Anesthesia PDF

anesthesia 1. A cardiac arrhythmia is ausculted during a preoperative examination in a three-year-old Thoroughbred gelding. The heart rate is 32 beats/minute [N=28-42] and the rhythm is regularly irregular. A representative ECG strip is shown below. What rhythm is this? Idiopathic bradycardia | At...

anesthesia 1. A cardiac arrhythmia is ausculted during a preoperative examination in a three-year-old Thoroughbred gelding. The heart rate is 32 beats/minute [N=28-42] and the rhythm is regularly irregular. A representative ECG strip is shown below. What rhythm is this? Idiopathic bradycardia | Atrial fibrillation | 2nd degree AV block | Sinus arrest 2nd degree AV block This is 2nd degree atrioventricular (AV) block. 2nd degree AV block is more common in horses at rest, when the heart rate is low, as it is associated with increased vagal (parasympathetic) tone. When sympathetic tone increases, as with exercise, excitement, pain, etc., the heart rate increases and AV block disappears. 2nd degree AV block can be diagnosed without an ECG. The rhythm is regularly irregular, the pause is equal to 2X the normal interval between contractions, the 4th heart sound (S4) is audible during the pause, and the irregularity disappears when the HR increases. Click this link to see this ECG with legend. Check out this Joint ACVIM/ECEIM Consensus Statement on Recommendations for Management of Equine Athletes with Cardiovascular Abnormalities. Refs: Wilson Clin Vet Advisor: The Horse, pp 55-8, Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. pp. 867-68 and Anesthesia & Analgesia for Vet Techs, 4th ed. pp. 20-1, 147-9. 2. Which drug is often used to control epilepsy (idiopathic seizures) when common metabolic and toxic causes have been ruled out? Pentobarbital | Phenobarbital | Secobarbital | Methohexital Phenobarbital These drugs are all barbiturates. Think of PHENObarb to control epilepsy/seizures. Can see agitation/excitement at first, or profound depression, so need to monitor. Methohexital is an ultra-short-acting barbiturates used to induce anesthesia. Pentobarbital and secobarbital are used primarily as euthanasia agents today. Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed., p. 1017, Papich, Saunders Handbook of Vet. Drugs: Sm and Lg An., 4th ed., Methohexital, Pentobarbital, Phenobarbital, Secobarbital. 3. Which one of the following types of nerve fibers normally respond to non-noxious stimuli like touch, pressure, and proprioception? A-beta | A-alpha | C | A-delta | B A-beta A-beta fibers normally respond to non-noxious stimuli, primarily touch, pressure, and proprioception. These are highly sensitive, low threshold receptors located in skin, muscles, and joints. Hypersensitization of pain pathways develops when sensory input is extreme or prolonged; new connections within the spinal cord develop, and response to A-beta receptors becomes painful as well. A-delta fibers and C fibers have specialized nerve endings that specifically respond to noxious/painful stimuli - these are the nociceptors. A-delta fibers have many low and some high threshold receptors that respond to mechanical and thermal stimuli. C fibers have primarily high threshold receptors that respond to many types of painful stimuli. A-delta receptors are highly sensitive; they respond quickly to transmit the 'first pain' response. The higher threshold C fibers respond later, providing the 'second pain' response. A-alpha fibers provide motor innervation to skeletal muscle. B fibers are found in the autonomic nervous system. See very good video overview of pain physiology - An introduction to pain pathways and mechanisms by Danielle R, Curran N, and Stephens R, from University College London Hospital, UK, and Lamont LA, DVM, Tranquilli WJ, & Grimm KA. 2000. Physiology Of Pain. Vet Clinics of NA: Small Animal Practice;30(4): 703-28. Refs: Gaynor & Muir Handbook of Vet Pain Mgt 2nd ed. pp. 14-9, Greene, Vet Anes and Pain Mgt Secrets pp. 323-5,. 4. Numerous pauses are heard on the Doppler of a dog anesthetized with isoflurane. The veterinary technician monitoring the dog is having trouble evaluating the heart rhythm from this electrocardiogram. Which of the following is the main problem? The paper speed is too slow | The wrong lead set up was used to record the ECG | Respiratory motion has distorted the baseline | This patient must be very large, the waveforms don’t fit on the paper Respiratory motion has distorted the baseline Respiratory motion has distorted the recording, causing the undulating wave-like baseline seen. To correct this, move the lead attachments further away from the chest, or select a different lead (Lead I or III) to see if this artifact remains. When the recording was corrected, second degree AV block was discovered, as seen in this ECG. This is a good example of one advantage of using a Doppler blood pressure monitor – since cardiac pulsations are continuously audible, it is obvious when an arrhythmia occurs. Refs: McCurnin's Clin Textbk for Vet Techs, 9th ed. pp. 860 and LP Tilly & NL Burtnick's, Eds. ECG for the SA Practitioner, pp. 96-7. 5. A 15-year-old horse is presented for chronic right forelimb lameness. Exam reveals a grade 3/5 lameness on the AAEP lameness scale (0/5 is sound, 5/5 is non-weight bearing) and mild sensitivity to hoof testers over the medial toe. Radiographs of the foot reveal the following. What is the most distal nerve block that is likely to improve this horse’s lameness? Low 4-point | Median and ulnar | Abaxial | Palmar digital | High 4-point Abaxial An abaxial nerve block is the most distal nerve blood that would alleviate this horse’s lameness; it usually desensitizes the entire foot. The palmar digital nerve block typically anesthetizes the heel portion (palmar/plantar ⅓) of the foot. The other nerve blocks listed are higher up the leg and would work, but are not necessary. In practice nerve blocks are not an exact science but these are good rules of thumb. There is a circular radiolucency visible at the solar margin of the third (distal) phalanx, consistent with a keratoma. This radiographic view is called a “65º dorsoproximal-palmarodistal oblique” or “solar margin view” because it highlights the solar margin of the third phalanx. Keratomas are benign masses that develop at the coronary band and grow down between the third phalanx and hoof wall. They cause lameness and radiolucency and must be removed surgically via hoof wall resection. Ref: Ross and Dyson, Diagnosis and Management of Lameness in the Horse, pp. 358-59. Images courtesy of Nora Grenager, VMD, DACVIM. 6. Which opioid choice provides good long-duration analgesia for mild to moderate pain in cats and can be given IM, IV, SQ, and transmucosally? Morphine | Oxymorphone | Buprenorphine | Naloxone | Butorphanol Buprenorphine Buprenorphine is one of the most popular and reliable opioid analgesics for use in cats. Cats are quite difficult to evaluate for pain; many studies of analgesic drugs have shown equivocal or variable result. However, buprenorphine has consistently provided good analgesia for cats with mild to moderate pain. It should not be used in patients with severe pain. Since it is a partial mu-agonist, it does not cause many of the side effects of pure mu-agonists such as nausea, vomiting, and dysphoria. Duration is long, six hours or more; onset is also long, 30 minutes to an hour in dogs and cats, depending on the route of administration. It is difficult to reverse as it binds very tightly to the mu-receptor. Buprenorphine can be given transmucosaly with almost 100% absorption as the pH of the feline mouth (8-9) favors this. It is also available as a transdermal patch for humans, but so far these have not been effective for use in cats. Excellent review of pain in cats: SA Robertson. Managing Pain in Feline Patients. Vet Clinics of NA: SA Practice 2008; 38: 1267–90. For a thorough review of physiology and clinical use of analgesia, check out Pain Management Guidelines for Dogs & Cats from the AAHA and the AAFP's Feline Acute Pain Scale from Colorado State Veterinary Medical Center. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 993. 7. Which choice is a consequence of overinflation of the endotracheal tube cuff? Tracheal necrosis | Increased Sp | Cyanosis | Lidocaine sensitivity | Choking Tracheal necrosis Overinflation of the cuff on an endotracheal tube can cause tracheal necrosis due to the pressure of the cuff on the mucosal lining of the trachea. Laryngospasm can result in cyanosis and hypoxia if the animal is not able to be intubated in a reasonable period of time. The CO2 may increase with overinflation, but the SpO2 would not increase, because the animal is not getting supplemental oxygen via the tube. Kelli Johnsen CVT, VTS (ECC) provides information on preventing tracheal trauma secondary to endotracheal intubation. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1071. 8. A young cat is under general anesthesia for a routine ovariohysterectomy. The technician notices that the cat has stopped breathing and her mucous membranes are a muddy blue color. The attached pulse oximeter is unable to detect a pulse. Of the following choices below, which one is the best next step? Ensure airway, oxygen supply, and breathing circuit are open | Give a specific sedative antagonist if available | Check for a pulse and measure blood pressure | Stop anesthetic administration and assess for cardiac arrest | Ventilate the cat  Stop anesthetic administration and assess for cardiac arrest Although all of the answers should be performed, there is little time to revive a patient in cardiac arrest. The first step should be stop administration of inhalant anesthetic and quickly assess cardiovascular status--i.e., check for pulse/heart rate. The technician should call for help to aid in a thorough assessment of the patient and to help perform cardiopulmonary resuscitation (CPR) if required. Even though patients that arrest under general anesthesia have a better chance for recovery, interruption of, or delay in, starting cardiac compressions is associated with poorer outcomes. The use of anesthetic monitors that constantly evaluate cardiovascular function and the presence of an anesthesia technician at all times has been shown to greatly improve outcome in cases with cardiac arrest. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. pp. 851-54. Image courtesy, Bill Rhodes. 9. What type of anesthetic breathing circuit is a Bain system when it is run at a high flow rate (~300 ml/kg/min)? Semi-closed system | Closed system | Open system | Nonrebreathing | Partial rebreathing Nonrebreathing A Bain anesthetic circuit run at a HIGH flow rate of ~300 ml/kg/min will not allow rebreathing of exhaled gasses so it is a nonrebreathing system. Remember that a Bain system is like a tube within a tube. New oxygen and anesthetic gas is inhaled down the inner tube, and exhaled gas exits through the outer tube. At MODERATE flow rates of ~20-300 ml/kg/min the Bain functions as a partial rebreathing system, and the animal rebreathes some of the exhaled gasses. Semi-closed and partial rebreathing systems are the same thing. They run at intermediate flow rates where fresh gas is delivered in excess of metabolic consumption, from about 10 ml/kg/min (large animals) to 30 ml/kg/min (small animals). A closed anesthetic rebreathing system only provides enough fresh gas flow to meet an animal's metabolic needs, a LOW flow rate of ~5-10 ml/kg/min (depending on animal size; flow is lower for larger animals and higher for smaller animals). Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. pp. 1025-27 and Tighe and Brown, Mosby's Comprehensive Review for Veterinary Technicians, 4th ed. p. 460. 10. In what position are dogs and cats typically intubated? Sternal | Dorsal | Standing | Sitting | Lateral Sternal Dogs, cats, and small ruminants are typically intubated in sternal recumbency. Horses, due to their large size, are typically intubated in lateral recumbency. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1032. 11. How can proper endotracheal tube placement be confirmed? SpO2 > 95% | Absence of a palpebral reflex | Expansion of the reservoir bag | Palpation of the neck | Normal breathing Palpation of the neck When palpating the neck, normally only one firm structure is present, the trachea. If you can feel two tubes, then the endotracheal tube is in the esophagus, not the trachea. If you feel only one firm tube, then the endotracheal tube is correctly placed in the trachea. An end tidal CO2 monitor can also show if you have correct placement (or not). If the tube placement is correct, then you will see a normal waveform. When a trach tube is misplaced into the esophagus, there is no waveform at all. Lastly, feeling breath moving out of the tube can also help confirm proper tube placement. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1032. 12. What key advantage do the alpha-2 agonists have over other sedatives? There is no advantage | Provide analgesia | Reversible | Able to be given orally | Less expensive  Provide analgesia The alpha-2 agonists provide analgesia in addition to sedation, whereas other sedatives, such as acepromazine and diazepam, do not. Combining the alpha-2 agonists with opioids increases the duration of analgesia. The duration will vary based on the opioid used. Dexmedetomidine can be reversed with atipamezole, while xylazine can be reversed with yohimbine. If these agents are fully reversed, their analgesic effects are also reversed. However, other sedatives’ effects can also be reversed (e.g., diazepam reversed with flumazenil), so this is not an advantage unique to alpha-2s. Dr. Sandra Allweiler provides this list of Drugs used to Relieve Pain. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 994. 13. Which of the following most correctly describes physiologic pain? Pain that originates from damage to peripheral nerves or the central nervous system | The sensation that results when electrolytes or other biochemical compounds are imbalanced | Pain that results when homeostasis is disturbed, as when dehydration is present | Pain caused by stretching, tension, or inflammation of viscera | A protective response to an actual or potentially damaging insult A protective response to an actual or potentially damaging insult Physiologic pain is a protective response to an actual or potentially damaging insult. Basically, this is a normal healthy pain response - an automatic mechanism to avoid or minimize injury, which initiates the physiologic and physical response to pain. Physiologic pain is also called nociceptive pain, as it involves the basic physiologic mechanisms of reception, transmission, and processing of stimuli that lead to perception of pain. Response to physiologic pain is behavioral, emotional, and physiologic; and both involuntary and voluntary. Classic example - when your hand touches something hot, you unconsciously withdraw, move away, and your heart rate increases, etc. The withdrawal and tachycardia are involuntary responses that occur almost immediately. The next event is behavioral and voluntary, where you move away, run cold water on the burn, and change how you handle the hot item, etc. The emotional component is when you exclaim "OUCH." Stretching, tension, or inflammation of viscera causes visceral pain, e.g. colic in horses. Neuropathic pain is caused by damage to neural tissue. See links with good pain information - Taxonomy of pain from the IASP, and Pain Management Guidelines for Dogs & Cats from the AAHA, and the AAFP. Refs: Gaynor & Muir Handbook of Vet Pain Mgt 2nd ed. pp. 14-30, 58, Greene, Vet Anes and Pain Mgt Secrets, pp. 323-7,. 14. Which one of the following combinations is necessary to perform a corneal scraping in a horse? Auriculopalpebral nerve block and topical proparacaine | Ophthalmic and lacrimal nerve blocks | Maxillary nerve block and intracameral tetracaine | Retrobulbar nerve block plus subconjunctival lidocaine | Infraorbital and supraorbital nerve blocks Auriculopalpebral nerve block and topical proparacaine An auriculopalpebral (AP) nerve block and topical proparacaine will enable examination and treatment of the cornea. Sedation may also be necessary in very painful or nervous horses. The auriculopalpebral nerve innervates the orbicularis oculi muscles. Blocking this nerve allows the examiner to hold the eyelids open easily, even though the horse can still feel the lids. A supraorbital nerve block desensitizes the upper eyelid; this is very helpful in addition to an AP and topical. Instillation of a topical anesthetic such as proparacaine onto the cornea is vital to allow manipulation, scraping for cytology, and debridement. The infraorbital and maxillary nerve blocks do not block any part of the eye. A retrobulbar nerve block is used for enucleation. An intracameral injection places anesthetic into the anterior chamber. This is invasive and not necessary for an ophthalmic exam. See a diagram of the locations of these blocks, courtesy Dr. JG Adams. Refs: Muir, Hubbell, Bednarski, and Skarda's Handbook of Veterinary Anesthesia, 4th ed. pp. 100-3, Muir and Hubbell's Equine Anesthesia, 2nd ed. pp. 221-3. 15. Which two drugs are contraindicated in animals with a history of seizures? Morphine, phenobarbital | Ketamine, diazepam | Xylazine, thiopental | Xylazine, ketamine  Xylazine, ketamine Ketamine and xylazine are contraindicated in animals with a history of seizures. Acepromazine was once thought to decrease seizure thresholds, but that information has since been proven incorrect. Thiopental is contraindicated in animals with history of asthma, because it can cause apnea, and in Greyhounds (Greyhounds have prolonged recoveries following anesthesia with thiopental due to a deficiency in the hepatic enzyme responsible for the first step in the metabolism of that drug). It is currently unavailable in the U.S. and Canada. Morphine should not be used in cases with high intracranial pressure (like head trauma after being hit by a car). Diazepam and phenobarbital are drugs used to TREAT seizures. Refs: Papich, Saunders Handbook of Vet. Drugs: Sm and Lg An., 4th ed., Acepromazine, Ketamine, Thiopental, Xylazine and Sams RA, Muir WW, Robinson EP. Comparative pharmacokinetics and anesthetic effects of methohexital, thiamylal, and thiopental in Greyhound dogs and non-Greyhound, mixed-breed dogs. Am J Vet Res 1985;46(8):1677-1683. STRATEGY HINT: This is a "frequency" question. That is, you can see how the choices "ketamine" and "xylazine" are repeated, twice. In this case, even if you have no idea what the right answer may be, simply narrowing down to the answer choices included most frequently increase your chances of picking correctly! Chances are that the correct choice will include the word that is repeated the most often. NOTE - if you know the correct answer without the aid of study tricks like this, choose the answer your brain tells you is correct. These kinds of study tricks are only a guide to use if you are lost, they are NOT a guarantee of getting the answer right every time. 16. Which anesthetic breathing system has the highest fresh gas flow rate during maintenance of anesthesia? Closed system | Partial rebreathing | Nonrebreathing | Open system | Semi-closed system Nonrebreathing In NONrebreathing systems, there is NO remixing of inhaled and exhaled gasses. These systems run at HIGH fresh gas flow rates, 100-300 ml/kg/min. A closed anesthetic rebreathing system only provides enough fresh gas flow to meet an animal's metabolic needs, about 5-10 ml/kg/min (depending on animal size; flow is lower for larger animals and higher for smaller animals). Semi-closed and partial rebreathing systems are the same thing. They run at intermediate flow rates where fresh gas is delivered in excess of metabolic consumption, from about 10 ml/kg/min (large animals) or 30 ml/kg/min (small animals). Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed., p. 1024 and Tighe and Brown, Mosby's Comprehensive Review for Veterinary Technicians, 4th ed. p. 460. 17. Ketamine is contraindicated for dogs having a history of which problem? Epilepsy | Bradycardia | Decreased intraocular pressure | Polyuria, polydipsia | Parvovirus Epilepsy Ketamine can cause seizures in some dogs (epilepsy is a form of seizures). Ketamine is contraindicated (do not use it) in dogs with increased intra-ocular pressure (like glaucoma) and it can also cause respiratory depression. Other contraindications include prior hypersensitivity reactions, animals to be used for human consumption, use of ketamine alone for general anesthesia, and increased CSF pressure or head trauma. Remember to protect a cat's eyes with ophthalmic ointment when using ketamine, because they remain open. Refs: Papich, Saunders Handbook of Vet. Drugs: Sm and Lg An., 4th ed., p. 427. 18. Which choice is the most likely adverse outcome if an endotracheal tube is placed that is too long for the size of the patient? Hyperventilation is stimulated | SpO2 is increased | Laryngospasm occurs | Dead space is significantly decreased | Only one lung is ventilated Only one lung is ventilated When an endotracheal tube is inserted too far into the airway, it can inadvertently be directed into only one lung instead of ventilating both lungs. This will cut down the anesthetic gas administered by half, making it difficult to keep the patient anesthetized. The other problem that may occur is an increase in the mechanical dead space because of the additional, unneeded length of the endotracheal tube. Harrie Phillips, a veterinary nurse in Australia, provides good instruction on correct placement of an endotracheal tube. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1030. 19. Which drug is the best choice for anesthesia in fish meant for human consumption in North America? Xylazine + potassium chloride | Tricaine methanesulfonate | Pentobarbital | Rapid chilling | 2-Phenoxyethanol Tricaine methanesulfonate Tricaine methanesulfonate (MS222, Tricaine mesylate) is the only anesthetic licensed in the United States and Canada for food fish intended for human consumption. At high doses, tricaine methanesulfonate is sometimes used to perform euthanasia in fish and amphibians. Metomidate hydrochloride (Aqua-Calm) can be used for sedation and anesthesia of ornamental fish. Click here for a review of fish sedation and anesthesia options, courtesy of the Canadian Council on Animal Care. Click here to see the AVMA's Guideline's for Euthanasia of Animals. Refs: The AVMA and Canadian Council on Animal Care. 20. On average, how often do soda lime (CO2 absorbent granules) in an anesthetic circuit need to be changed? 80 cumulative hours of anesthesia | Before every surgery | After 6-8 hours of use | Only when 100% of the granules have changed color | Weekly After 6-8 hours of use On average, soda lime should be changed after 6-8 hours of use. This will depend on the size of the patient, the duration of anesthesia, and the oxygen flow rate. A higher oxygen flow rate will deplete the granules more quickly than running a closed or semi-closed system with lower flow rates. If an anesthetic machine has sat unused for longer than 30 days, you should also change the granules. Harrie Phillips provides additional guidelines on use, changing, and disposal of soda lime. Ref: Tighe and Brown, Mosby's Comprehensive Review for Veterinary Technicians, 4th ed. p. 458. 21. At what pressure should a leak occur around the endotracheal tube after intubation? 20 cm H2O | There should be no leak around the tube | 95 mm Hg | 80 mcg | 2200 psi 20 cm H2O Leakage of air around the endotracheal tube at 20 cm H20 helps to ensure that the cuff is not over-inflated or under-inflated during anesthesia. Remember that the muscles will continue to relax as a deeper plane of anesthesia is achieved, and the cuff should be retested at that time. If the cuff is over-inflated, pressure necrosis or tearing of the trachea can occur. If the cuff is under-inflated, there is increased exposure of the surgical team to waste anesthetic gasses, and it may be more difficult to keep the patient anesthetized. The American Animal Hospital Association (AAHA) provides this info on Equipment Preparation prior to an anesthetic event. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1033. 22. What does low solubility tell you about an inhalant anesthetic? May be corrosive to rubber gaskets | Faster induction and recovery | More chance of cardiovascular complications | Requires higher oxygen flow rates | Greater risk of under-dosing Faster induction and recovery Low solubility means fast induction and recovery. Minimum alveolar concentration (MAC) is the minimum concentration of anesthetic in the alveolar gas that prevents a physical response in 50% of animals exposed to a surgical stimulus. It is a is a measure of anesthetic potency (inversely related). Desflurane has the highest MAC at 7.2 in dogs, 9.8 in cats, and 7.6 in horses. Isoflurane has the lowest MAC of 1.2 in dogs, 1.63 in cats, and 1.31 in horses. Sevoflurane has an intermediate MAC of 2.1 in dogs and 2.58 in cats, and 2.31 in horses. Inhalants with high potency have a lower MAC (need less drug to achieve anesthetic plane). These are also more soluble in blood and tissues; e.g., isoflurane is more soluble, desflurane is less soluble. The requirement (%) for less soluble drugs is greater, but induction is much faster. Anesthesia occurs only when the concentration of inhalant in the blood and alveoli are equal. Less soluble drugs achieve this equilibrium faster. Since there is also less drug in the tissues, recovery is also faster compared to more soluble drugs. When the vaporizer is turned off, alveolar levels drop rapidly, followed by blood and tissue levels. Refs: McCurnins’ Clinical Textbook for Vet Techs, 9th ed., p. 1018, Fossum’s Small Animal Surgery, 5th ed., pp. 125-39, and Auer and Stick Equine Surgery, 5th ed., p. 301. 23. When using a stylet to stiffen an endotracheal tube, how far past the tip should it extend? 1-2 mm | A stylet should never be used | 3-5 centimeters | It should not extend past the end at all | At least 2 inches to allow it to enter the laryngeal folds first It should not extend past the end at all If a stylet is needed to stiffen an endotracheal tube, it should never extend past the end of the tube. Numerous styles of stylets exist, and the size and length will vary depending on the size and length of the endotracheal tube. There is an increased chance of trauma to the laryngeal folds, oropharynx, and trachea if the stylet extends past the end of the endotracheal tube. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1030. 24. Before it is safe to attempt endotracheal intubation of an anesthetized dog, what two reflexes should be ABSENT? Triceps and Golgi tendon | Palpebral and stretch | Crossed extensor and corneal | Patellar and tonic vibration | Pedal and swallowing Pedal and swallowing Loss of both the pedal reflex, tested by pinching the toes and looking for withdrawal of the limb, and the swallowing reflex indicate readiness for intubation. Palpebral and corneal reflexes can be used to assess depth of anesthesia, but may still be present during intubation. A stretch reflex is contraction of a muscle in response to a lengthening stretch; the Golgi tendon reflex is the opposite reaction. Triceps and crossed extensor reflexes are mechanically tested with a reflex hammer. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1030. 25. A dog at first seems to relax but then begins paddling with all four legs during induction of anesthesia with alfaxalone after premedication with acepromazine and hydromorphone. He has nystagmus and is tossing his head back and forth. What is the correct interpretation of this scenario? Alfaxalone dose was inadequate, this is Stage II excitement | Overdose - this is Stage IV with seizure activity due to cerebral hypotension | Anaphylactic reaction to hydromorphone, epinephrine should be given at once | Allergic reaction to the soy bean oil in alfaxalone | Hydromorphone or thiopental injected perivascularly, causing pain Alfaxalone dose was inadequate, this is Stage II excitement This is the involuntary excitement of American Society of Anesthesia (ASA) Stage II anesthesia due to an inadequate dose of alfaxalone. As consciousness is diminishing, loss of voluntary control of movement occurs in ASA Stage II. Patients can have violent jerky movements and often "paddle" with all 4 limbs. Horses and cattle, and some dogs and cats, exhibit nystagmus. Excessive salivation and vomiting may also occur. ASA Stage II begins with loss of consciousness and lasts until a regular respiratory pattern is present. Ideally, ASA Stage II is bypassed with induction. Remember that muscle relaxation is poor with ketamine, and some patients may be stiff or show myoclonus with propofol or etomidate. This may be a temporary sign that will pass or another drug may be needed to produce relaxation. For more, see Anesthesia Monitoring (listed under "Lecture Schedule") by Lyon Lee DVM, PhD. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed., p. 1008-59. 26. Which of the following effects are seen with high doses of isoflurane? High systolic arterial blood pressure, loss of corneal reflex | Nausea, tachypnea | Respiratory depression, seizures | Decreased cardiac output, ileus | Tachycardia, vomiting Decreased cardiac output, ileus Ileus and decreased cardiac output can be seen with high doses of isoflurane. At high doses, cardiac output is DECREASED by all the inhalant anesthetics (including isoflurane) due to myocardial depression. This effect is most significant at deeper levels of anesthesia and in sick patients. At anesthetic concentrations of isoflurane used clinically, cardiac output is usually within the normal range but blood pressure may be decreased due to vasodilation. Vomiting, nausea, and respiratory depression are also seen with high doses of isoflurane. Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed., p. 1018. 27. Using a Bain non-rebreathing circuit, what is the recommended flow rate for animals weighing less than seven kg? 20-40 ml/kg/min | Only rebreathing systems are used in animals this small | 5 L/min | 300-400 ml/kg/min | 50-100 ml/lb/sec 300-400 ml/kg/min A Bain anesthetic circuit run as a non-rebreathing system needs to be set at 300-400 ml/kg/min. This high of a flow rate helps to prevent rebreathing of exhaled gasses. This rate is ~ 2-3 times the respiratory minute volume (RMV), or the amount of air that moves in and out of the lungs in a minute. This is calculated as tidal volume X respiratory rate. Remember that a Bain system is like a tube within a tube. New oxygen and anesthetic gas is inhaled down the inner tube and exhaled gas exits through the outer tube. At lower flow rates (i.e., 20-300 ml/kg/min) the Bain circuit functions as a PARTIAL rebreathing system and the animal rebreathes some of the exhaled gasses. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. pp. 1024, 1320. 28. Which choice can be used in combination with ketamine to induce anesthesia in horses? Guaifenesin | Halothane | Phenobarbital | Naloxone Guaifenesin Guaifenesin is an anti-tussive (anti-cough) and decongestant that also works as a muscle relaxant. It is used, in conjunction with ketamine, to support a smooth anesthesia induction and recovery in horses. It can also be part of "double-drip" or "triple-drip" injectable anesthesia used for short procedures (with just ketamine or with ketamine and xylazine, respectively). Naloxone is a reversal agent against opiate drugs (in horses, butorphanol (Torbugesic®) is the most commonly used opiate). Halothane gas would not work to mask a horse down into anesthesia because you would expect problems restraining the animal in the excitement phase of induction. Phenobarbital is a long-acting barbiturate used to control epilepsy/seizures, not induce. Refs: Clin Textbook for Vet Technicians, McCurnin & Bassert, 9th ed. p. 1018, Plumb's Vet Drug Handbook, 7th ed. pp. 653-6 and Tighe & Brown, Mosby's Comprehensive Review for Vet Techs, 2nd ed. p. 302. 29. Diazepam use is contraindicated in which of the following medical conditions? Seizure disorders | Heart disease | Liver failure | Hypertension | Diabetes mellitus Liver failure Avoid diazepam, a benzodiazepine, in patients with significant hepatic disease. Serious hepatotoxicity has been reported with diazepam use in CATS. Chronic oral use is generally NOT recommended in cats. Also use with caution in patients with renal disease, shock, coma, and aggression. Refs: Papich, Saunders Handbook of Vet. Drugs: Sm and Lg An., 4th ed. p. 228. 30. Which one of the following choices correctly pairs the drug listed with its receptor and action? Atipamezole - alpha-2 receptor - antagonist | Propofol - gamma-amino butyric acid (GABA) receptor antagonist - general anesthesia | Butorphanol - mu receptor agonist - analgesia | Detomidine - beta-1 agonist - sedation | Acepromazine - dopamine receptor agonist - sedation Atipamezole - alpha-2 receptor - antagonist Atipamezole is an alpha-2 receptor antagonist, used to reverse the effects of drugs such as xylazine, medetomidine, dexmedetomidine, detomidine, and romifidine. Other alpha-2 antagonists include yohimbine and tolazoline. Acepromazine is a sedative drug that antagonizes dopamine receptors in the brain. Butorphanol is a opioid drug that is a kappa receptor agonist but a mu receptor antagonist. Detomidine is an alpha-2 receptor agonist that produces profound sedation, used mostly in horses. Propofol is a general anesthetic that enhances the activity of the GABA receptor. Refs: Grimm, Tranquilli, and Lamont's Essentials of Anes and Analgesia in SA, 2nd ed. pp. 29-48, Muir, Hubbell, Bednarski, and Skarda's Handbook of Veterinary Anesthesia, 4th ed. pp. 44-50. 31. An anesthetic patient that meets the criteria for American Society of Anesthesiologists (ASA) level I (normal, healthy animal) should be monitored how often? At least once/minute | Whenever the multiparameter monitor indicates a significant change | Monitoring is only required if the anesthetic event lasts longer than 30 minutes | Only during induction and recovery | Every 5 minutes Every 5 minutes Healthy patients, placed in physical status category ASA I, should be monitored every 5 minutes. For ASA patients II through V, even more frequent monitoring would be indicated. If you monitor too infrequently, you can miss subtle changes in the anesthetic depth or patient condition. ASA categories: ASA I - a normal healthy patient ASA II - a patient with mild systemic disease ASA III - a patient with severe systemic disease ASA IV - a patient with severe systemic disease that is an immediate threat to life ASA V - Moribund patient who is not expected to survive without the operation Here is a review by Dr. Phil Zeltzman covering How ASA Scores Help to Make Anesthesia Safer. The American College of Veterinary Anesthesia (ACVA) provides these guidelines for monitoring anesthetized veterinary patients. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. pp. 1033-34. 32. A cat is anesthetized for ovariohysterectomy (OHE) with isoflurane in oxygen after premedication with atropine, acepromazine, and hydromorphone intramuscularly, and induction with midazolam and ketamine intravenously. As the surgeon exteriorizes the first ovary for ligation, the cat’s heart rate, blood pressure, and respiratory rate begin to increase rapidly, but she does not move. Which of the following is the next best step? Decrease the fluid rate | Put the cat on a ventilator | Increase analgesia with a dose of hydromorphone IV | Raise the inspired oxygen flow rate to a higher setting | Increase the isoflurane vaporizer setting Increase analgesia with a dose of hydromorphone IV Increase the analgesia: The cat is experiencing a sympathetic response to pain from surgical stimulation. Response during OHE is common at the skin incision, and with tension on the ovarian ligaments or uterus. Surgical stimulation raises sympathetic tone, which increases heart rate (HR), blood pressure (BP), and respiratory rate (RR). This is known as nociception since the animal is unconscious and therefore cannot "feel" pain. Increases in HR, RR, or BP do not necessarily mean the patient feels pain as awareness is lost before the autonomic response to surgery. The sympathetic responses may be blunted by increasing the concentration of inhalants, however, this does not address the underlying cause which is sympathetic response to pain. Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed., pp. 1035-9 and table 31.3, Thomas & Lerche Vet Anes and Analgesia for Vet Techs, 4thed. pp. 142-3, 177. 33. Non-steroidal anti-inflammatory drugs (NSAIDs) have a maximal effect when administered prior to surgery. What physiologic parameter needs to be monitored during the surgery if the animal is on preoperative NSAIDs? Blood pressure | Heart rate | Respiratory rate | Anesthetic depth | Bleeding Blood pressure Blood pressure needs to be closely monitored when non-steroidal anti-inflammatory drugs (NSAIDs) are given before a procedure because blood flow to the kidneys can be compromised with hypotension. This has the potential to cause significant renal insult and can lead to renal damage/failure after recovery from the anesthetic event. Administer intravenous fluids if a drop in blood pressure is seen. NSAIDs should not be administered to patients who have already received corticosteroids or aspirin, as this combination increases the chance of gastric ulceration. The American Animal Hospital Associations provides this information on NSAID use. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 990. 34. What is the main drawback of an inhalant anesthetic with a high solubility (high blood-gas partition coefficient) compared to an inhalant with a low solubility? Requires special vaporizer because boiling point is close to room temperature | Slower induction and recovery | Toxic metabolites in liver more likely to accumulate | Cost | Can corrode plastic components to breathing circuit Slower induction and recovery High solubility (i.e., high blood-gas partition coefficient) means the gas is mostly absorbed into the body tissues, causing slow anesthetic induction and slow recovery. Halothane has a relatively high solubility (~2.5), which is part of why is not used often in the U.S. anymore (though still sometimes overseas). Sevoflurane and isoflurane have much lower blood-gas partition coefficients (~0.68 and 1.46, respectively) and therefore have more rapid induction, recovery, and response to changes in anesthetic depth. Desflurane has a very low blood-gas partition coefficient (low solubility) but requires a special vaporizer because its boiling point is close to room temperature. Methoxyflurane has the highest solubility (blood-gas partition coefficient) but is no longer readily available. Refs:Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed., p.1018. 35. What fresh gas flow rate should you use during induction when using a semi-closed rebreathing anesthetic system in small animals? 5X the calculated maintenance flow | 200 ml/kg/min | 30-50 ml/kg/min | 100 ml/kg/min | 2-3 L/10# body weight to a maximum of 5 L 100 ml/kg/min The fresh gas flow rate during induction and recovery using a semi-closed rebreathing system is about 100 ml/kg/min, which is 2 to 3 times the calculated maintenance flow. During the maintenance of anesthesia, the flow is reduced to 30-50 ml/kg/min in small animals. The minimum flow rate is equal to the patient's metabolic oxygen requirement. Most use a higher flow rate as it is safer and requires less monitoring. Another consideration is the minimum setting required by the vaporizer, as some are not accurate at extremely low flows. Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed., p. 1024. 36. The image below is a cardiac waveform taken from an electrocardiogram of horse that was recorded using Lead I with a base-apex setup. Which of the following corresponds to the ventricular repolarization? P wave, #1 | QRS wave, #3-5 | T wave, #6-7 | A wave, #2 T wave, #6-7 The T wave, 6-7 represents ventricular repolarization. The ventricular muscle is refractory to another depolarization at this time while the membrane potential of the myocardial cells reset to normal. The shape and direction of each waveform is affected by placement of leads and the recording selected. In horses, the best ECG is obtained using Lead I with electrodes attached in the base-apex arrangement. The P wave will be positive, the QRS is negative, and the T wave varies in direction. With Lead III, the direction of waveforms is opposite. Refs: McCurnin's Clin Textbk for Vet Techs, 8th ed. pp. 935-7 and Thomas & Lerche Anes & Analgesia for Vet Techs, 4th ed. pp 145-7. 37. If inhalant anesthetic agents A and B are compared, which property would result in the quickest induction, recovery, and changes in depth of anesthesia? High solubility | High levels of analgesia | Low vapor pressure | Low blood-gas partition coefficient | High minimum alveolar concentration Low blood-gas partition coefficient Inhalant anesthetic agents with a low blood-gas partition coefficient have higher speeds of induction, recovery, and changes in depth of anesthesia. Sevoflurane and isoflurane are examples of inhalant agents with low blood-gas partition coefficients. Sevoflurane is less soluble than isoflurane leading to more rapid induction and recovery with this agent. Solubility determines the speed of anesthetic induction and recovery; therefore induction and recovery is slower with halothane than with sevoflurane or isoflurane. A gas with a very high solubility such as ether has an even slower induction and recovery. Desflurane, with its extremely low solubility, has the fastest induction and recovery, but is not typically used in veterinary medicine. Neither sevoflurane nor isoflurane provide any analgesia after recovery, and their minimum alveolar concentration (MAC) is a measure of the potency of the agent. The higher the MAC, the less potent the drug. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1018. 38. To what should the anesthetic dial be set to help most patients reach a surgical plane of anesthesia with most anesthetic agents? (MAC = minimum alveolar concentration) Equal to MAC | 2.0 x MAC | 3.0 x MAC | There is no standard setting | 1.5 x MAC 1.5 x MAC For most anesthetics and most patients, a dial setting of 1.5 x MAC is utilized to reach a surgical plane of anesthesia. The minimum alveolar concentration (MAC) of an anesthetic agent is the percent concentration at which 50% of patients would not respond to surgical stimulation. Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed., p. 1018. 39. A 50-lb mixed breed dog is heavily sedated with dexmedetomine and butorphanol given intravenously for repair of a laceration. His mucous membranes are pale, capillary refill time is 2 seconds, heart rate is 56 beats per minute [N=70-120 bpm], respiratory rate is 10 breaths per minute [N=18-34 brpm]. Which of the following is the next best step? Place an intravenous catheter and bolus 10 ml/kg of lactated Ringer's | Give an anti-cholinergic intramuscularly for the slow heart rate | Perform an electrocardiogram to determine the type of bradycardia | Administer an NSAID IV to counter surgical pain | No treatment is necessary, this is normal with alpha-2 agonists No treatment is necessary, this is normal with alpha-2 agonists No treatment is necessary. Bradycardia is a very common side effect of alpha-2 agonists in all species. It is a reflex, a baroreceptor response to the initial hypertension that is caused by intense vasoconstriction. The hypertension causes a reflex increase in vagal tone, which slows the heart rate (HR). In this case, the low HR should not automatically be treated, as this would further increase blood pressure (BP) and the workload of the heart. If the HR gets too slow or very dysrhythmic, or BP drops too low, reversal with atipamezole is indicated. Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. pp. 994, 1104 and Thomas & Lerche Vet Anes and Analgesia for Vet Techs, 4th ed. pp. 62-64. 40. Which choice indicates that the soda lime granules in a CO2 absorbent canister have become exhausted? Crystals become hard and turn off-white | Color change from purple to pink, crystals become powder | Crystals remain white, but patient won't stay asleep | Color stays pink, regardless of CO2 exposure | Color changes to brown and liquid accumulates at the base of the canister Crystals become hard and turn off-white Crystals become hard and turn off-white. The purpose of a canister of soda lime granules is to absorb carbon dioxide (CO2) from exhaled anesthetic gasses. Fresh absorbent crystals are white and can be crushed. But exhausted, saturated crystals become a distinct off-white color and are hard. Most granules contain a pH-sensitive dye that becomes visible as the absorbent granules become saturated. (The color itself is not so important as the color changing). A color change from white to purple or violet typically indicates that the CO2 scavenger granules have become saturated with CO2, but this color change does not always happen, and will dissipate after a few hours. The Veterinary Anesthesia and Analgesia Support Group is a nice online resource for anesthesia information. Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed., p. 1058. 41. Which anesthetic drug choice can cause seizures if given in high doses? Xylazine | Isoflurane | Phenobarbital | Diazepam | Ketamine Ketamine Dissociative anesthetics, like ketamine or tiletamine, can cause seizures at high doses. Three of the other drugs listed here are sedatives, not anesthetics (diazepam, xylazine, and phenobarbital), and isoflurane is an inhalant anesthetic. Diazepam injectable is often used to stop seizures, while phenobarbital tablets can be used to help prevent seizures. Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1017, Papich, Saunders Handbook of Vet Drugs, 4th ed., methohexital and Tighe and Brown, Mosby's Comprehensive Review for Vet Techs, 2nd ed. p. 301. 42. What might happen if you push the oxygen flush button on an anesthetic machine? The patient may start to wake up | Oxygen is flushed out of the system | Anesthetic gas concentration goes up in the breathing circuit | The patient will go to a deeper anesthetic plane | Flow rate increases The patient may start to wake up The patient may wake up. The oxygen flush sends pure oxygen into the breathing circuit, BYPASSING the vaporizer. Anesthetic gas concentration DECREASES and patients may start to wake up. Remember you should NOT hit the oxygen flush button if the pop-off valve is closed, or when using a non-rebreathing system, because you can deliver dangerously high airway pressure to the patient. STRATEGY HINT: This is a kind of "frequency" question. That is, you can see how the choice "wake up" and the "deeper anesthesia" choice are flip sides of the same possibility. (Kind of like being repeated, or increased frequency!). Chances are that the correct choice will include the choice that is repeated the most often. In this case, even if you have no idea what the right answer may be, simply narrowing down to the two answer choices will increase your chances of picking correctly to 50:50! Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1024. 43. Which choice is the most effective and practical measure to decrease exposure of the surgical staff to waste anesthetic gasses (WAGs) in the surgical suite? Limiting procedures to less than 30 minutes | Leaving doors to surgical suite open | Keeping oxygen flow rate under two l/min | Use of a scavenger system | Wearing N95 surgical masks Use of a scavenger system The use of either an active (central vacuum) or passive (charcoal absorbers) scavengers are recommended for removal of exhaled WAGs. Regular anesthetic machine service and leak monitoring helps to decrease WAGs. Change charcoal absorbers after 50 grams of weight gain to ensure that they can effectively remove exhaled anesthetic gasses. Management of waste anesthetic gasses is covered by OSHA. Every hospital's safety manual should include OSHA’s guidelines. Ref: Tighe and Brown, Mosby's Comprehensive Review for Veterinary Technicians, 4th ed. p. 461. 44. For anesthetics, what does the minimum alveolar concentration (MAC) measure? Minimum safe concentration | The rate of metabolism through the kidneys | Anesthetic fat solubility | Speed of expected induction | Measure of anesthetic potency Measure of anesthetic potency Minimum alveolar concentration (MAC) is a measure of anesthetic potency. Technically, it is the minimum concentration of anesthetic in the alveolar gas that prevents a physical response in 50% of animals exposed to a surgical stimulus. Because you want to be 100% sure that an animal is completely anesthetized, you usually use MULTIPLES of MAC to determine vaporizer settings (e.g., 1-2X MAC) to guarantee appropriate anesthesia during surgery. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1018. 45. Propofol is a non-barbiturate agent used to induce anesthesia. Which statement is most correct about propofol? Open vials must be discarded within one hour of opening | Slowly cleared from the body | Provides minimal to no analgesic effects | Highly irritating if accidentally injected perivascularly | Can cause respiratory excitation if given too rapidly Provides minimal to no analgesic effects Propofol has little to no analgesic effects. Be sure to identify whether the propofol being used has preservatives in it, as this can affect how long it can be used once open. Propofol without preservatives should be discarded within six hours of opening. Propofol-28 is good for 28 days after opening. Propofol is RAPIDLY cleared and is NOT particularly irritating to tissues if it goes outside the vein accidentally. Propofol can cause APNEA (breathing stops) if given too rapidly. Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1016 and Papich, Saunders Handbook of Vet. Drugs: Sm and Lg An., 4th ed. p. 684. 46. A nine-year-old male castrated Doberman is presented for a 1-cm ulcerated skin mass on his sternum. The owner would like it removed because when the pet is resting, pressure on the mass causes it to bleed. The dog has a history of dilated cardiomyopathy which is currently well-controlled with medication. Which one of the following combinations is the most safe and humane anesthesia protocol for this procedure? Alpha-2 adrenergic agonist, inhalant anesthesia, opioid | Ketamine, inhalant anesthesia | Inhalant anesthesia, acepromazine, alpha-2 adrenergic agonist | Ketamine, local anesthesia, alpha-2 adrenergic agonist | Opioid, benzodiazepine, local anesthesia Opioid, benzodiazepine, local anesthesia A protocol with an opioid, a benzodiazepine, and local anesthesia is the safest route for this dog with dilated cardiomyopathy (DCM). For removal of a small skin mass, mild sedation and local anesthesia is adequate. Combinations of an opioid (such as morphine or butorphanol) and a benzodiazepine (such as midazolam) for sedation are typically safe for most patients with heart disease. Local injectable anesthesia (lidocaine, bupivicaine) can be used to numb the area of the mass to allow for removal. Alpha-2 adrenergic agonists should be avoided in pets with heart disease due to bradycardia, conduction disturbances, myocardial depression, and arrhythmogenicity. Ketamine is a positive inotrope, however it may cause excitation leading to increased oxygen demand and may trigger myocardial ischemia and arrhythmias. Inhaled maintenance anesthetics may cause a dose-dependent depression of myocardial contraction and should be used judiciously. Refs: Cote, Clinical Vet Advisor–Dogs and Cats, 4th ed. pp. 1129-30 and Papich, Saunders Handbook of Veterinary Drugs, 4th ed. 47. A five-year-old gelding is going to be placed under general anesthesia and maintained with isoflurane and controlled mechanical ventilation for a left front metacarpophalangeal joint arthroscopy. If he is placed in right lateral recumbency, which lungs will suffer the most ventilation/perfusion (V/Q) mismatch during the procedure? Right | Depends on arterial blood gas reading | Left | Dorsocaudal lung fields | None; this is prevented by assisted ventilation Right In right lateral recumbency, the right lungs are on the down side and the left lungs are on the upper side. The down side will have reduced lung volume which causes ventilation/perfusion (V/Q) mismatch and impaired gas exchange in the lungs on the bottom. Horses in dorsal recumbency will have decreased lung volume in the dorsal lung fields, and if they have abdominal enlargement (i.e., gas-distended bowel or pregnant uterus) the GI compartment/diaphragm exerts even more pressure on the thorax, worsening ventilation of the dorsal lung fields. Horses undergoing anesthetic procedures over 90 minutes, or any horse under gas anesthesia, are typically maintained on controlled mechanical ventilation to increase alveolar ventilation and mitigate V/Q mismatch. Furthermore, it is recommended to place an arterial catheter for monitoring arterial blood gas in these patients. This allows the anesthetist to stay on top of hypoxemia or pH disturbances. Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. pp. 1049-53, Hornof, et al, "Effects of lateral recumbency on regional lung function in anesthetized horses" in American Journal of Vet Research and Mosing and Senior, “Maintenance of equine anaesthesia over the last 50 years: Controlled inhalation of volatile anaesthetics and pulmonary ventilation” in Equine Vet Journal. 48. Which choice is the most likely reason for the reservoir bag to overinflate during an anesthetic procedure? Hyperventilation | Active scavenger is too strong | Oxygen pressure is too high | Patient is experiencing conscious pain | Pop-off valve is closed Pop-off valve is closed Several things can cause a reservoir bag to distend, including accidental pop-off valve closure, a flow rate that is too high, or inadequate scavenging. When you close the pop-off valve to bag a patient, ALWAYS REMEMBER TO REOPEN IT. The oxygen flow rate needs meet the patient’s oxygen requirement, but increasing levels too high is wasteful. If the active scavenger is malfunctioning or the charcoal canister is exhausted, the reservoir bag can also fill up. The main elements of a pre-surgery anesthetic machine check include: 1. Are oxygen tank levels adequate? 2. Is the vaporizer filled? 3. Are the pressure checks ok? 4. Are the soda lime and charcoal canisters fresh? Here is a good summary of anesthetic equipment preparation courtesy of the American Animal Hospital Association (AAHA) that shows a good picture of a pop-off valve. Ref: Tighe and Brown, Mosby's Comprehensive Review for Veterinary Technicians, 4th ed. p. 470. 49. Which one of the following regional nerve blocks does not affect sensory function but blocks motor function of the upper eyelid, and is indicated to allow complete ophthalmic examination in the horse? Ocular | Auriculopalpebral | Supraorbital | Zygomatic | Frontal Auriculopalpebral The auriculopalpebral nerve, located along the dorsal zygomatic arch of the eye, provides motor innervation to the upper orbicularis oculi muscle. Anesthesia of this nerve prevents the horse from being able to blink the eye and facilitates complete ophthalmic examination. The frontal nerve is a branch of the trigeminal nerve and provides sensory innervation to the upper eyelid. Click here to see a good summary on ophthalmology surgical emergencies in horses, with images, courtesy of the American College of Veterinary Surgeons (ACVS). Refs: Smith, Large Animal Internal Medicine, 4th ed. pp. 793-8. 50. How can laryngospasms be prevented during anesthetic induction in cats? Give acepromazine one hour prior to induction | Administer atropine 15 minutes prior to induction | Avoid inhalant anesthesia | Use a Murphy tube | Pretreat with topical lidocaine Pretreat with topical lidocaine Laryngospasm can be prevented by applying lidocaine gel or spray to the larynx before attempting intubation. Remember that topical lidocaine requires 15-20 seconds for full effect. Laryngeal spasm is a problem for cats, small ruminants, and swine. It can be associated with overzealous manipulation of the larynx either by a laryngoscope or during the intubation itself. Dr. Pacharinsak presents other Challenges in Feline Anesthesia, including laryngospasm. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1030. 51. Minimum alveolar concentration (MAC) is the minimum concentration of anesthetic in the alveolar gas that prevents a physical response in 50% of animals exposed to a surgical stimulus. It is a measure of anesthetic potency. Which of the following inhalant anesthetics has the lowest MAC? Isoflurane | Halothane | Methoxyflurane | Sevoflurane | Desflurane Desflurane Desflurane has the highest minimum alveolar concentration (MAC) at 7.2 in dogs, 9.8 in cats, and 7.6 in horses. Sevoflurane has an intermediate MAC of 2.1 in dogs, 2.58 in cats, and 2.31 in horses. Isoflurane has low MAC of 1.2 in dogs, 1.63 in cats, and 1.31 in horses. Methoxyflurane has a MAC of 0.23 in dogs, but is expensive and not currently being produced. Halothane is rarely used in clinical practice any more (MAC = 0.88). Inhalants with high potency have a lower MAC (need less drug to achieve anesthetic plane). These are also more soluble in blood and tissues; e.g., isoflurane is more soluble, desflurane is less soluble. The requirement (%) for less soluble drugs is greater, but induction is much faster. Anesthesia occurs only when the concentration of inhalant in the blood and alveoli are equal. Less soluble drugs achieve this equilibrium faster. Since there is also less drug in the tissues, recovery is also faster compared to more soluble drugs. When the vaporizer is turned off, alveolar levels drop rapidly, followed by blood and tissue levels. Refs: McCurnins’ Clinical Textbook for Vet Techs, 9th ed., p. 1018, Fossum’s Small Animal Surgery, 5th ed., pp. 125-39, and Auer and Stick Equine Surgery, 5th ed., p. 301. 52. Which of the following correctly describes the concept of 'wind-up' pain? Slowly increasing a painful stimulus in order to increase the patient’s tolerance | Damaged peripheral receptors are non- responsive to stimuli that would normally elicit a painful response | Situation when reversal agents for alpha-agonists and opioids are ineffective for pain control | Using opioids and NSAIDs to preemptively address pain in surgical patients | Central sensitization of nociceptors responding to bombardment by painful stimuli Central sensitization of nociceptors responding to bombardment by painful stimuli Wind-up, or central sensitization, occurs when spinal neurons have been bombarded by high-intensity or repetitive nociceptive impulses from C-fibers. This causes nociceptors (pain receptors) to respond over a wider area than usual, at faster rates, and to stimuli that are not normally painful. The wind-up pain response has two parts. 1. Hyperalgesia: it takes less input to stimulate a painful response (i.e., the pain threshold is set lower). 2. Allodynia: the body has a painful response to stimuli that would normally NOT be painful (i.e., non-pain fibers are recruited). Wind-up can occur in response to tissue damage from trauma or surgery. This chronic pain is very difficult to treat so prevention is key. N-methyl-D-aspartate (NMDA) receptors in the spinal cord are activated in the wind-up phenomenon. Ketamine, an NMDA receptor antagonist, is used to help prevent the development of wind-up. Other NMDA antagonists include methadone, amantadine, and dextromethorphan. Opioid receptors are also down-regulated during wind-up, making pain control difficult. Gabapentin is a GABA-analogue that blocks calcium- dependent channels on neurons, suppressing stimulated neurons so it is often part of the therapeutic plan to prevent/treat wind-up. Click here for a very thorough presentation of Neurophysiology of Pain and Delivery of Pain Care by Dr. Mark Epstein. Refs: Gaynor & Muir Handbook of Vet Pain Mgt 2nd ed. pp. 34-6, 57-9, Greene, Vet Anes and Pain Mgt Secrets, pp. 323-33, 345-7. 53. A dog under anesthesia for teeth cleaning develops a sinus bradycardia (heart rate 50 beats per minute). One minute following treatment with atropine, an irregular rhythm is identified on the Doppler and the electrocardiogram, seen in the image below. Which of the following correctly identifies this rhythm? Respiratory sinus arrhythmia | Atrial fibrillation | Second degree AV block | Asystole Second degree AV block This dog has second degree AV block which is a failure of conduction through the AV node. Atropine may initially cause a transient slowing of heart rate (HR) and AV block as low doses stimulate presynaptic inhibitory receptors. As drug level increases, muscarinic blockade predominates and HR increases. The ECG is characterized by occasional P waves without a QRS that follows. There is a 'dropped beat' as the ventricles do not contract. This rhythm is heard as a pause equal to 2X the normal R-R interval. Click this link to see image of the ECG with explanation. Refs: McCurnin's Clin Textbk for Vet Techs, 8th ed. pp. 942-3, Thomas & Lerche Anesthesia & Analgesia for Vet Techs, 4th ed. p. 58. 54. Which of the following inhalant anesthetics typically has slowest induction/recovery time? Desflurane | Guaifenesin | Sevoflurane | Propofol | Isoflurane Isoflurane Isoflurane has the slowest induction and recovery times because it is the most soluble of the inhalant anesthetics available. Minimum alveolar concentration (MAC) is the minimum concentration of anesthetic in the alveolar gas that prevents a physical response in 50% of animals exposed to a surgical stimulus. It is a measure of anesthetic potency (inverse correlation). Isoflurane has the lowest MAC of 1.2 in dogs, 1.63 in cats, and 1.31 in horses. Sevoflurane has an intermediate MAC of 2.1 in dogs and 2.58 in cats, and 2.31 in horses. Desflurane has the highest MAC at 7.2 in dogs, 9.8 in cats, and 7.6 in horses. Inhalants with high potency have a lower MAC (need less drug to achieve anesthetic plane). These are also more soluble in blood and tissues; e.g., isoflurane is more soluble, desflurane is less soluble. The requirement (%) for less soluble drugs is greater (such as Desflurane), but induction is much faster. Anesthesia occurs only when the concentration of inhalant in the blood and alveoli are equal. Less soluble drugs achieve this equilibrium faster. With less soluble drugs, since there is less drug in the tissues, recovery is faster compared to drugs with a lower MAC. When the vaporizer is turned off, alveolar levels drop rapidly, followed by blood and tissue levels. Propofol and guaifenesin are not inhalant anesthetics. Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1018, Fossum’s Small Animal Surgery, 5th ed. pp. 125-39, and Auer and Stick Equine Surgery, 5th ed. p. 301. 55. Which choice is a normal capnography reading for a patient under inhalant anesthesia? 20-30 mm H20 | 75-85 ml/min | 95-100% | 40-55 mm Hg | 0-10 mg Ag 40-55 mm Hg Capnography measures the amount of expired carbon dioxide (CO2) in each breath. This is commonly called ‘end-tidal CO2.’ The level should rise to 40-55 mm Hg at peak expiration when under inhalant anesthesia. In awake animals, the level should be 0 mm Hg on inhalation and rise to 35-45 mm Hg on exhalation. Higher levels of CO2 indicate hypoxia and the anesthetist needs to take measures to increase the patient’s oxygen intake and decrease the CO2 levels. Lower levels indicate that the patient is hyperventilating. In this article, Samantha Adshead, VTS (Anesthesia & Analgesia) helps explain capnography, including interpreting the readout on a multiparameter monitor. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. pp. 850, 1044. 56. Which sedative typically causes the least cardiac and respiratory depression? Butorphanol | Dexmedetomidine | Acepromazine | Propofol | Xylazine Acepromazine Acepromazine causes the least respiratory and cardiac depression of the agents listed. It is a phenothiazine tranquilizer that causes mild sedation. It is often given in combination with other agents as a pre-anesthetic or for stronger sedation. Unlike other sedatives listed it provides no analgesic effects. Xylazine and dexmedetomidine are alpha-two adrenergic agonists used as sedatives. They can cause significant bradycardia, reduction in cardiac output, hypotension, cardiac arrhythmias, and respiratory depression. Butorphanol is a mixed opioid agonist–antagonist. It can cause respiratory depression and bradycardia. Propofol can lead to significant respiratory depression, apnea, bradycardia, and decreased cardiac contractility. Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed., p. 1013 and Papich, Saunders Handbook of Vet. Drugs: Sm and Lg An., 4th ed. p. 1. 57. Which choice is important to remember when administering inhalant anesthesia to a bird? Inhalant anesthesia is very irritating to their trachea and lung tissues | The trachea terminates directly into the right and left lungs | They have complete tracheal rings | The trachea is located to the right of the esophagus | Their MAC is much lower than in mammals They have complete tracheal rings The avian trachea is made of completely closed cartilaginous rings which can be damaged by a cuffed endotracheal tube. Therefore, use only NON-cuffed endotracheal tubes for intubation. A Cole tube is an example of an non-cuffed endotracheal tube. If you use a cuffed tube in birds, the pressure of the inflated cuff can damage the mucosal layer in the trachea and lead to tracheal stricture. Remember to place a mouth gag AFTER intubation to prevent the beak of larger birds from severing the endotracheal tube during anesthetic recovery. This article by Sondra Biggs, LVT, provides more in-depth information on avian anesthesia. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 771. 58. Post-anesthetic induction apnea commonly occurs with propofol. What piece of monitoring equipment is used to measure carbon dioxide levels to ensure ventilation efforts are not excessive? 6-lead ECG monitor | Esophageal stethoscope | End-tidal CO2 | Capnograph | Pulse oximeter Capnograph Carbon dioxide (end tidal CO2) levels are measured using a capnograph monitor. Pulse oximeters measure oxygen saturation of RBCs, and an ECG measures cardiac electrical conduction. An esophageal stethoscope is used to more directly monitor cardiac pulses during anesthesia. Additional monitoring during anesthesia may include invasive and noninvasive blood pressure monitoring, thermometers, and measurements of respiratory rate and volume. Ref: Bassert and Thomas, McCurnin's Clinical Textbook for Vet Technicians, 9th ed. p. 1038. 59. Which of the following choices are effects of acepromazine in dogs and cats? Anti-emesis, vasodilation | Anti-arrhythmic, hypertension | Muscle relaxation, analgesia | Increase blood pressure, muscle tremors | Sedation, piloerection Anti-emesis, vasodilation Acepromazine is a phenothiazine that causes vasodilation while acting as an anti-emetic, sedative, muscle relaxant, and anti- arrhythmic. Acepromazine has two main mechanisms of action: - blocks peripheral alpha-1 receptors, which produces vasodilation and hypotension - blocks dopamine receptors in the brain, which produces sedative, anti-emetic, and anti- arrhythmic effects, as well as causing muscle relaxation It does NOT provide analgesia or cause vasoconstriction. Refs: Tranquilli, Thurmon, and Grimm's Lumb & Jones Veterinary Anesthesia, 4th ed. pp. 207-9, Muir, Hubbell, Bednarski, and Skarda's Handbook of Veterinary Anesthesia, 4th ed. pp. 29-34, and Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1013. 60. Why are atropine or glycopyrrolate (anti-cholinergics) often given as a premedication to dogs and cats before inducing anesthesia with ketamine or tiletamine (dissociative anesthetics)? Decreases salivation | Slows the heart rate | Helps keep eyes closed | Lowers body temperature | Increases airway secretions Decreases salivation Anti-cholinergics like atropine or glycopyrrolate are given as pre-meds to DECREASE salivation, DECREASE airway secretions, and INCREASE heart rate. They do NOT affect whether eyes are open or closed, but they do DILATE the pupils. Remember that many anesthetic drugs (like opiates, barbiturates, and gas anesthetics) promote bradycardia (slowed heart rate) and some dissociative anesthetics (like ketamine, tiletamine) cause excessive salivation. Refs: Papich, Saunders Handbook of Veterinary Drugs: Sm & Lg An., 4th ed. pp. 61, 361 and Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1013. 61. A low-pressure system check on an anesthetic machine monitors for leaks between or in which part(s) of the system? Flowmeter to patient | Pressure manometer | Soda lime canister to scavenger system | Endotracheal tube to flutter valves | Oxygen connector to Y tubes Flowmeter to patient A low-pressure check detects leaks in the anesthetic system from the flowmeter to the patient. This includes the vaporizer, flutter valves, soda lime canister, endotracheal tube, rebreathing bag, delivery hoses, and pop-off valve. Low pressure monitoring ensures that there are no leaks in the anesthetic system contributing waste anesthetic gasses into the surgical suite air and ensures that adequate vaporized anesthetic is reaching the patient. Here is an article covering both high- and low- pressure system checks for the oxygen delivery system and anesthetic machine. Ref: Tighe and Brown, Mosby's Comprehensive Review for Veterinary Technicians, 4th ed. P. 462. 62. A young female dog under inhalant anesthesia for ovariohysterectomy has the following arterial blood gas findings. Which one of the following choices is the most accurate interpretation of these findings? Hypoventilation leading to respiratory acidosis | Metabolic acidosis due to intravenous potassium supplementation error | Metabolic alkalosis due to H+ sequestration | Respiratory alkalosis resulting from too-frequent mechanical ventilation | Metabolic acidosis due to fluid loss Hypoventilation leading to respiratory acidosis Hypoventilation under anesthesia leading to respiratory acidosis is the most likely explanation for the findings on this dog. DEcreased pH=acidosis and INcreased PaCO2 with INcreased HCO3 indicates primary respiratory acidosis with incomplete metabolic compensation. Notice that although there is compensation the pH is not completely normalized (it takes time). PaO2 is higher than the reference range for an animal breathing room air despite hypoventilation because a dog under inhalant anesthesia is breathing nearly 100% oxygen. PaO2 is expected to be closer to 500 mm Hg with oxygen supplementation under anesthesia. Appropriate mechanical ventilation should correct the increased PaCO2 and acidemia quickly. Refs: See this informative article in dvm360 and this helpful reference on the Cornell University eclinpath website. 63. Which drug can reverse the effects of xylazine (an alpha2-adrenergic agonist with analgesic and sedative effects)? Pralidoxime | Yohimbine | Diazepam (Valium®) | Propofol | Atropine Yohimbine Yohimbine is the reversal agent for xylazine. Yohimbine is also an antidote for amitraZ, the drug used to treat generalized demodicosis. Remember "X goes with Y and Y goes with Z." Remember 2 things about xylazine: 1. Cattle are EXTREMELY SENSITIVE; cow xylazine dose is about 1/10 the dose in dogs or horses 2. Xylazine is used as an EMETIC in CATS (causes vomiting) Pralidoxime is used to treat organophosphate toxicity, along with a sedative for seizures (e.g., diazepam (Valium®) or pentobarbital) and atropine. Refs: Papich, Saunders Handbook of Vet. Drugs: Sm and Lg An., 4th ed. p. 853 and Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed., p. 1015. 64. Which of the following inhalant anesthetics is the least soluble? Isoflurane | Halothane | Desflurane | Propofol | Sevoflurane Desflurane Desflurane is the least soluble of the inhalant anesthetics available and therefore has the fastest induction and recovery times. Minimum alveolar concentration (MAC) is the minimum concentration of anesthetic in the alveolar gas that prevents a physical response in 50% of animals exposed to a surgical stimulus. It is a is a measure of anesthetic potency (inverse correlation). Desflurane has the highest MAC at 7.2 in dogs, 9.8 in cats, and 7.6 in horses. Isoflurane has the lowest MAC of 1.2 in dogs, 1.63 in cats, and 1.31 in horses. Sevoflurane has an intermediate MAC of 2.1 in dogs and 2.58 in cats, and 2.31 in horses. Inhalants with high potency have a lower MAC (need less drug to achieve anesthetic plane). These are also more soluble in blood and tissues; e.g., isoflurane is more soluble, desflurane is less soluble. The requirement (%) for less soluble drugs is greater, but induction is much faster. Anesthesia occurs only when the concentration of inhalant in the blood and alveoli are equal. Less soluble drugs achieve this equilibrium faster. Since there is also less drug in the tissues, recovery is also faster compared to more soluble drugs. When the vaporizer is turned off, alveolar levels drop rapidly, followed by blood and tissue levels. Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed., p. 1018, Fossum’s Small Animal Surgery, 5th ed., pp. 125-39, and Auer and Stick Equine Surgery, 5th ed., p. 301. 65. The basic physiology of pain includes 5 phenomena that occur along the pain pathway to alert the patient to a painful stimulus. Which of the following choices occurs in the cerebral cortex? Projection | Transmission | Modulation | Transduction | Perception Perception Perception is the final step in the transfer of a painful stimulus. The patient perceives the presence of pain once neurons in the cerebral cortex are activated. Step I - transduction of the stimulus by pain receptors (or nociceptors) located on the nerve endings of A-delta and C fibers. Step 2 - transmission to the dorsal horn of the spinal cord, where the cell bodies of the nociceptors are located. Here, the signal is (3) modulated – amplified and/or suppressed. It is then (4) projected to the midbrain periaqueductal gray area, the thalamus, and parts of the brainstem, where it is further processed and sent to the cerebral cortex for (5) perception. Modulation also occurs in the cortex both before, during, and after perception. Note: some omit projection, and call it 'central transmission'. See very good video overview of pain physiology: An introduction to pain pathways and mechanisms by Danielle R, Curran N and Stephens R, from University College London Hospital, UK. Lamont LA, DVM, Tranquilli WJ, & Grimm KA. 2000. Physiology Of Pain. Vet Clinics of NA: Small Animal Practice;30(4): 703-28. Refs: Gaynor & Muir Handbook of Vet Pain Mgt 2nd ed. pp. 17-9, 26-8, Greene, Vet Anes and Pain Mgt Secrets pp. 323-5. 66. What is the primary use of xylazine in cattle? Chemical restraint | Maintenance of anesthesia | Prevention of hypoxemia | Postoperative pain control | Induction of anesthesia Chemical restraint Xylazine is primarily used for chemical restraint in cattle. Xylazine has sedative, analgesic, and muscle relaxation properties. Cattle are very sensitive to xylazine - the bovine dose is about 1/10 the dose used in dogs or horses. It is often used in combination with ketamine and butorphanol. Bloat and hypoxemia are a concern when you use xylazine in cattle at doses that cause recumbency. Xylazine is reversed with yohimbine, atipamezole, or tolazoline. 67. How do you prevent laryngospasm in cats during induction and maintenance of anesthesia? Pre-medicate with acepromazine | Pre-medicate with atropine | 1-2% Lidocaine spray | Avoid halothane 1-2% Lidocaine spray Prevent laryngospasm by spraying larynx with 1-2% lidocaine. Laryngeal spasm is primarily a CAT problem associated with overzealous manipulation of the larynx by laryngoscope or during intubation. AVOID BENZOcaine in cats. Commercial topical preparations of benzocaine (like "Cetacaine") shouldn't be used because of reports of methemoglobinemia associated with their use. Pigs are also prone to laryngospasm. Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. pp. 1033-34 and Cote Clinical Veterinary Advisor: Dogs and Cats, 4th ed. pp. 576-78. 68. Which of the following most correctly describes neuropathic pain? The sensation that results when nociceptors are activated | A painful response caused by damage to neural tissue | Amplification of the peripheral pain response | Pain that results when homeostasis is disturbed, as when disease is present | Intense discomfort caused by stretching, tension, or inflammation of viscera A painful response caused by damage to neural tissue Neuropathic pain (NP) is a painful response caused by damage to neural tissue. Axons, cell bodies, and the myelin sheath of nerve fibers located peripherally or centrally may all be affected. NP results from direct injury to nerve tissue, or occurs indirectly following the inflammatory and neurochemical response to injury of non-neural tissue. Humans describe NP as shooting or stabbing pain, often with a continuous burning sensation. It is most often seen in patients with chronic pain, but recent information suggests it develops with acute pain also. Sensitization occurs such that hyperalgesia (a heightened response to painful stimuli) and allodynia (pain response to stimuli that are not normally painful) both develop and last long after the initial injury is healed. Neuropathic pain is possible but does not occur in all patients with neuropathy. Many medications have been used to treat NP - gabapentin, originally developed and used for seizures, is used often. See proceedings article on Neuropathic pain in veterinary patients by Dr. Mark Epstein, and an excellent review : Mathews KA. 2008. Neuropathic Pain in Dogs and Cats: If Only They Could Tell Us If They Hurt. Vet Clin of NA, SA Practice; (38): 1365–1414. Refs: Gaynor & Muir Handbook of Vet Pain Mgt 2nd ed. pp. 57-9, 267-9, 439, Greene, Vet Anes and Pain Mgt Secrets pp. 323-30, 345-7. 69. A dog is presented with a lick granuloma and treated with gabapentin to address neuropathic pain. What is the most common side effect that clients may see in pets treated with gabapentin? Increased thirst | Miotic pupils | Excessive salivation | Sleepiness | Rear leg weakness Sleepiness Sleepiness is the most commonly seen side effect of gabapentin, usually only at higher doses. Note, the human gabapentin elixir can contain xylitol and should not be used on veterinary patients as this is associated with hypoglycemia and seizures. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 996. 70. Which of the following correctly describes the phenomenon of hyperalgesia? Increased response to a stimulus that normally produces pain | Stimuli that are not normally painful produce a pain response | A protective response to an actual or potentially damaging insult | Lack of or decreased response to stimuli that usually cause pain | A greater analgesic effect seen with treatment of a patient in pain Increased response to a stimulus that normally produces pain Hyperalgesia is an increased response to a stimulus that normally produces pain. Injured areas can develop an exaggerated response or hypersensitivity to painful stimuli. The cascade of events following trauma and inflammation transforms the response of nociceptors in the area. They respond at lower levels of input and to stimuli that normally would not produce such a strong response. Components of damaged tissue stimulate influx of activated inflammatory cells that secrete numerous mediators - a 'sensitizing soup' develops in the injured area. Bradykinins, cytokines, serotonin, histamine, and many others amplify the inflammatory response and the resulting pain. Pain is defined as protective response to an actual or potentially damaging insult. Allodynia is the triggering of a painful response by stimuli that are not normally painful. Hypoalgesia is a decreased response to normally painful stimuli. Refs: Gaynor & Muir Handbook of Vet Pain Mgt 2nd ed., pp. 28-36, 57-9, Greene, Vet Anes and Pain Mgt Secrets, pp. 323-7. 71. Which one of the following choices best explains the concept of balanced anesthesia? Maintaining the same ratio of anesthetic gas to oxygen used | Matching the dose of anesthetic drug used to the body weight of patient | Using similar drugs to achieve full anesthetic depth | Use of two or more drugs to achieve the desired level of anesthesia | Varying the dose of the anesthetic used to maintain a certain depth Use of two or more drugs to achieve the desired level of anesthesia Balanced anesthesia is the use of two or more drugs to achieve the desired level of anesthesia using agents with complimentary effects. Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed., p. 1011. 72. When is the best time to change the activated charcoal cartridges that anesthetic machines use to scavenge anesthetic gasses? When indicator on label indicates that the charcoal is exhausted | Daily | Following 30 hours of use | After 50 grams of weight gain | Weekly After 50 grams of weight gain Activated charcoal canisters (i.e., F/air) used to scavenge anesthetic gasses should be changed after 50 grams of weight gain. This may take one day or weeks, depending on the machine usage. Weight gain is dependent on the size and respiratory rate for the patient. There is no indicator on the label, but there is a chart to record weight changes. If you instead change it based on the hours of use, this can result in a canister not being changed at the correct time. If not changed on schedule, the anesthetic gasses will not be removed, and will instead be released into the room environment, thus increasing staff exposure to waste anesthetic gasses (WAGs) Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1029. 73. What is the oxygen content administered to a patient being manually ventilated with a bag valve mask (BVM, Ambu bag) using room air? 89% | 43% | 21% | 10% | 67% 21% Room air contains approximately 21% oxygen and 78% nitrogen. The remaining 1% is composed of minor gasses including carbon dioxide, argon, neon, helium, and xenon. When a patient is receiving inhalant anesthesia, it is mixed with 100% oxygen. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 640. 74. How long before an anesthetic procedure can a diabetic dog or cat be safely fasted? Half day and withhold insulin | 6 pm the evening before surgery | Midnight of day of procedure | 2-4 hours | They should never be fasted 2-4 hours Fast diabetic animals for 2-4 hours before anesthesia. Monitor their blood glucose before, during, and after anesthesia so that you can give insulin can as indicated. Obesity has increased the incidence of diabetes in the pet population. A diabetic pet may require anesthesia for dental procedures, neutering or diabetic complications. The American Animal Hospital Association provides these Fasting Guidelines for dogs and cats. Ref: American Animal Hospital Association Global Assets Anesthesia Guidelines. 75. Which of the following inhalant anesthetics is most soluble? Propofol | Sevoflurane | Isoflurane | Guaifenesin | Desflurane Isoflurane Isoflurane is the most soluble of the inhalant anesthetics available and therefore has the slowest induction and recovery times. Minimum alveolar concentration (MAC) is the minimum concentration of anesthetic in the alveolar gas that prevents a physical response in 50% of animals exposed to a surgical stimulus. MAC is expressed as a percentage. It is a is a measure of anesthetic potency (inverse correlation). Isoflurane has the lowest MAC of 1.2% in dogs, 1.63% in cats, and 1.31% in horses. Sevoflurane has an intermediate MAC of 2.1% in dogs and 2.58% in cats, and 2.31% in horses. Desflurane has the highest MAC at 7.2% in dogs, 9.8% in cats, and 7.6% in horses. Inhalants with high potency have a lower MAC (need less drug to achieve anesthetic plane). The lower the MAC value, the more soluble the anesthetic in blood, fat, and tissues; e.g., isoflurane is more soluble, desflurane is less soluble. The requirement (%) for less soluble drugs is greater, but induction is much faster. Anesthesia occurs only when the concentration of inhalant in the blood and alveoli are equal. Less soluble drugs achieve this equilibrium faster. Since there is also less drug in the tissues, recovery is also faster compared to more soluble drugs. When the vaporizer is turned off, alveolar levels drop rapidly, followed by blood and tissue levels. Propofol and guaifenesin are not inhalant anesthetics. Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed., p. 1018, Fossum’s Small Animal Surgery, 5th ed., pp. 125-39, and Auer and Stick Equine Surgery, 5th ed., p. 301. 76. Which choice is the best way to increase the amount of anesthetic gas present in the reservoir bag when managing inhalant anesthesia for a dog or cat? Disconnect the animal from the circuit to allow room air to flow in | Gently squeeze both sides of patient’s chest twice with open palms | Turn down the vaporizer | Increase the oxygen flow rate | A quick push on the flush valve Increase the oxygen flow rate The best method to safely increase the volume of gas in the reservoir bag is to turn up the flow meter to increase the oxygen flow rate. If the flush valve is used, only oxygen is used to fill the reservoir bag, with no anesthetic gas. This could allow the patient to enter a lighter plane of anesthesia and also has the potential of over-pressurizing the lungs. Disconnecting the circuit is unsafe - it allows the gas in the reservoir bag to escape into the room without the benefit of a scavenger. Turning down the vaporizer would lighten the plane of anesthesia, but will not fill up the reservoir bag. Clapping the chest walls is difficult with a fully draped surgical patient, and would have no effect on increasing the gas in the reservoir bag. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1028. 77. Which one of the following choices is the correct explanation of the function of a pulse oximeter? Amplifies the pulse rate and oxygenation of venous blood without touching patient | Measures the oxygen saturation of hemoglobin and pulse rate | Automatically measures and records the pulse rate and rhythm | Measures carbon dioxide concentration after every 10th pulse | Detects the flow of blood through small arteries and measure blood pressure Measures the oxygen saturation of hemoglobin and pulse rate A pulse oximeter is used primarily to measure the oxygen saturation of hemoglobin in arterial blood. A stable pulse is required for a good measurement, so the heart rate will also be measured. An esophageal stethoscope amplifies the sound of the heart to allow monitoring at a distance. An electrocardiogram (ECG) records heart rate and rhythm. A doppler monitor detects the flow of blood through small arteries and can be used to measure blood pressure. Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed., p. 845. 78. During which phase of anesthesia is the American Association of Anesthesiologists (ASA) classification for risk of adverse outcomes assigned? At the time the appointment is scheduled | Preanesthetic | Induction | Recovery | Maintenance Preanesthetic An anesthetist assigns the ASA status during the preanesthetic phase. This phase is also when the preanesthetic sedation and analgesics are chosen and administered. The patient’s health status and stability before anesthesia determines the ASA physical status. ASA classifications range from I-V, from healthy/minimal risk to moribund/high risk (see below). An increase in ASA status increases the chances of anesthesia-related death. ASA I - normal and healthy, minimal anesthetic risk ASA II - mild systemic disease ASA III - severe systemic disease ASA IV - severe systemic life-threatening disease ASA V - extreme anesthetic risk, patient may not survive without surgery Any emergency is assigned an “E” in addition to the ASA classification. For example: A dog with gastric torsion admitted for emergency surgery would be ASA IV E. The American Animal Hospital Association (AAHA) provides these Guidelines for assignment of ASA status. Here is a review by Dr. Phil Zeltzman covering How ASA Scores Help to Make Anesthesia Safer. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1011. 79. When might epidural anesthesia be contraindicated in a cow with dystocia? If the fetus is alive | It should always be performed | If Caesarian-section is likely | When planning vaginal delivery | Possible candidate for fetotomy When planning vaginal delivery Epidural anesthesia can be contraindicated in cases where vaginal delivery is the planned method of delivery because it means the cow will not be able to assist in delivering the calf. Epidural anesthesia helps minimize the pain caused by vaginal manipulation of a dystocia. However, sometimes the cow will become recumbent, which can be contraindicated when trying to pull a calf. It also reduces the force of uterine contractions so manipulation is easier to accomplish. Refs: Bassert and Thomas, McCurnin’s Clinical Textbook for Veterinary Technicians, 8th edition, p. 965. 80. Which piece of monitoring equipment is the best choice to confirm whether an endotracheal tube is accidentally placed in the esophagus or not? Esophageal stethoscope | Capnometer | Doppler blood pressure | Electrocardiograph (ECG) | Pulse oximeter Capnometer A capnometer measures CO2 levels and can confirm proper placement of an endotracheal tube. This image shows a CO2 monitor -- the endotracheal tube would be connected to the open end of the monitor; this information is sent to a screen for review. An end tidal CO2 (ETCO2) reading is obtained when a capnometer is attached between the endotracheal tube and the anesthetic system. If there is NO readout from the capnometer, then the endotracheal tube is probably in the esophagus. You should not find measurable CO2 in the esophagus. Here is a review by Jenny Flynn LVT, covering capnography and anesthesia. Here is a typical capnograph, showing exhalation on the left side and inhalation on the right side. You attach a capnometer to the endotracheal tube to get the capnograph. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1057. 81. Which one of the following is the most correct explanation of how electrical defibrillation works in patients with cardiac arrest? Re-starts all myocardial cells at once, eliminating the unorganized rhythm and poor contractility seen with fibrillation | Reroutes electrical signals from the pacemaker to the SA node | Accentuates strength of depolarization wave generated by pacemaker cells; they overwhelm fibrillation waves and restart cardiac rhythm | Abnormal myocardial cells that are fibrillating are cauterized | Shock stops all cells in heart simultaneously, allowing pacemaker cells to regain control of myocardial contraction Shock stops all cells in heart simultaneously, allowing pacemaker cells to regain control of myocardial contraction Shock stops all cells in heart simultaneously, allowing pacemaker cells to regain control of myocardial contraction. Defibrillation is performed with electrical shock to stop the activity of all myocardial cells at once. Essentially, the heart is put into asystole, to allow the pacemaker cells to regain control of the cardiac rhythm. Pacemaker cells can produce an effective depolarization and contraction only when the myocardial cells are able to respond. They must not be actively contracting (or fibrillating) or in a refractory period. Click here to download Vet Emergency and Critical Care with CPR guidelines for animals. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. pp. 852-54. 82. A seven-week-old female intact domestic short hair (DSH) kitten weighing 1.5 kg is presented for an eye enucleation. When should food be withheld prior to anesthesia? Just after administration of pre-anesthetic NSAIDs | 1-2 hours before induction | This patient should not be fasted | Full day preceding hospital admittance | 6 pm the night prior to surgery 1-2 hours before induction Due to their small size and lack of glucose stores, animals less than 2 kg should not be fasted longer than 2 hours prior to anesthesia. Before anesthesia, routine fasting prevents gastric regurgitation of food into the esophagus or mouth that can cause aspiration into the lungs. Regurgitation can also lead to esophageal strictures due to the high acidity of the gastric fluid. The American Animal Hospital Association provides these Fasting Guidelines for dogs and cats. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 1011. 83. Which advanced monitoring method is most indicated and helpful if there is a concern that hypoxemia, hypoventilation, and hypotension may occur during inhalant anesthesia? Central venous access | End-tidal CO2 monitoring | Arterial catheterization | Manual bagging 3-4 times/minute | Measure urine production Arterial catheterization Arterial catheters allow direct arterial blood sampling which can be used to assess pulmonary function and for direct blood pressure measurements. This is routinely done on most horses undergoing inhalant anesthesia. Remember that only arterial blood can be used to measure oxygen transfer from the lungs. Venous blood returning to the heart has already off-loaded the oxygen to the cells and uploaded carbon dioxide for removal by the lungs. Blood gas measurements can be used to evaluate partial pressure of carbon dioxide and oxygen in the blood. If these values may need to be tested repeatedly, placing a catheter is safer and easier on the patient and for the person having to collect the samples. End-tidal CO2 is an indirect measurement of ventilation; manual bagging is not a monitoring method; and urine production can give an idea of kidney function, but is best used over a longer period of time. Natasha Summerfield covers the Why, When, and How of Arterial Catheters, while Dr. Stein provides a step-by-step process of setting up the measuring devices and catheter placement. Ref: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed. p. 560. 84. A 12-year-old Warmblood mare has been sedated intravenously with a combination of xylazine and butorphanol for dental evaluation because she has been dropping feed. You listen to the heart immediately after sedation and note a heart rate of 20 beats per minute [Normal = 28-44 bpm] with an occasional “dropped” beat; the horse is standing quietly. What is the most appropriate action to take next? Nothing; this is a normal response | Prepare a dose of naloxone to reverse the butorphanol | Prepare a dose of atropine to increase heart rate | Prepare a dose of yohimbine to reverse the xylazine | Prepare a dose of dobutamine to improve cardiac contractility Nothing; this is a normal response Nothing; this is a normal response. Bradycardia commonly occurs immediately after induction of sedation with alpha-two agonists, such as xylazine, in horses. This bradycardia is sometimes accompanied by transient second degree atrioventricular block and a decreased respiratory rate. Atropine is an antimuscarinic agent that increases the heart rate. It is rarely indicated in these cases and is associated with an increased risk of colic. Butorphanol is a mixed opioid kappa agonist–mu antagonist and may uncommonly cause bradycardia. Opioid reversal with naloxone would not be indicated because the butorphanol is not likely the cause of the bradycardia. In addition, reversal of a mixed agonist-antagonist is not complete. The effects of the alpha-2 agonists can be reversed with yohimbine, tolazoline, or atipamezole. This is unnecessary when the horse is standing quietly with a heart rate of 20 bpm and second degree atrioventricular block. Dobutamine is a beta-one agonist and increases cardiac contractility with little effect on the heart rate. Refs: Bassert, Beal and Samples, McCurnin's Clinical Textbook for Veterinary Technicians, 9th ed., p. 1014, Papich, Saunders Handbook of Vet. Drugs: Sm and Lg An., 4th ed. pp. 850-851. 85. Which one of the following anesthetic drugs is contraindicated in patients with congestive heart failure? Diazepam | Dexmedetomidine | Etomidate | Butorphanol tartrate | Midazolam Dexmedetomidine Dexmedetomidine, an alpha-2 adrenergic agonist, is contraindicated in cardiac patients. Potential adverse effects include bradycardia, atrioventricular block and possible death due to circulatory failure. Benzodiazepines (e.g., diazepam, midazolam) and opioids (e.g., butorphanol) are generally safe in cardiac patients. Etomidate, an injectable anesthetic, may be a useful alternative to propofol in cardiac patients because it has minimal cardiovascular effects. Refs: The Merck Veterinar