Podcast
Questions and Answers
What is the relationship between MAC and anesthetic potency?
What is the relationship between MAC and anesthetic potency?
Which of the following factors can alter a patient's MAC?
Which of the following factors can alter a patient's MAC?
Isoflurane is commonly used in which of the following species?
Isoflurane is commonly used in which of the following species?
What is a significant cardiovascular effect of Isoflurane?
What is a significant cardiovascular effect of Isoflurane?
Signup and view all the answers
Which anesthetic agent is known for having the lowest blood-gas partition coefficient?
Which anesthetic agent is known for having the lowest blood-gas partition coefficient?
Signup and view all the answers
What is a primary action of Doxapram?
What is a primary action of Doxapram?
Signup and view all the answers
What potential adverse effect can occur with Doxapram administration?
What potential adverse effect can occur with Doxapram administration?
Signup and view all the answers
How does Nitrous Oxide affect MAC levels?
How does Nitrous Oxide affect MAC levels?
Signup and view all the answers
Which inhalation agent is characterized by a need for a precision vaporizer due to high vapor pressure?
Which inhalation agent is characterized by a need for a precision vaporizer due to high vapor pressure?
Signup and view all the answers
What happens when desiccated carbon dioxide absorbent is exposed to Isoflurane?
What happens when desiccated carbon dioxide absorbent is exposed to Isoflurane?
Signup and view all the answers
Which effects are primarily associated with alpha2-agonists used in anesthetic protocols?
Which effects are primarily associated with alpha2-agonists used in anesthetic protocols?
Signup and view all the answers
What is a key monitoring consideration when using alpha2-agonists during anesthesia?
What is a key monitoring consideration when using alpha2-agonists during anesthesia?
Signup and view all the answers
Which pharmacodynamic effect of alpha2-agonists is most crucial during surgical procedures?
Which pharmacodynamic effect of alpha2-agonists is most crucial during surgical procedures?
Signup and view all the answers
When administering alpha2-agonists, which side effect should veterinary technicians be vigilant for?
When administering alpha2-agonists, which side effect should veterinary technicians be vigilant for?
Signup and view all the answers
Which statement about alpha2-agonists is true in their application in veterinary anesthesia?
Which statement about alpha2-agonists is true in their application in veterinary anesthesia?
Signup and view all the answers
What is an important consideration when deciding to use alpha2-agonists for anesthesia?
What is an important consideration when deciding to use alpha2-agonists for anesthesia?
Signup and view all the answers
Which of the following best describes a risk associated with the use of alpha2-agonists?
Which of the following best describes a risk associated with the use of alpha2-agonists?
Signup and view all the answers
In the context of alpha2-agonists, what role does patient monitoring play during anesthesia?
In the context of alpha2-agonists, what role does patient monitoring play during anesthesia?
Signup and view all the answers
Which adjunctive agent is often used alongside alpha2-agonists to enhance analgesia?
Which adjunctive agent is often used alongside alpha2-agonists to enhance analgesia?
Signup and view all the answers
What mechanism of action do alpha2-agonists employ to produce their sedative effects?
What mechanism of action do alpha2-agonists employ to produce their sedative effects?
Signup and view all the answers
What is a common effect of propofol when administered as an anesthetic?
What is a common effect of propofol when administered as an anesthetic?
Signup and view all the answers
Which injectable anesthetic is primarily noted for its short duration of action and is a steroid molecule?
Which injectable anesthetic is primarily noted for its short duration of action and is a steroid molecule?
Signup and view all the answers
Which pharmacological property is associated with halogenated inhalation anesthetics that affects their delivery?
Which pharmacological property is associated with halogenated inhalation anesthetics that affects their delivery?
Signup and view all the answers
What is a potential adverse effect of using dissociative anesthetics?
What is a potential adverse effect of using dissociative anesthetics?
Signup and view all the answers
What is the recommended handling procedure for propofol after it has been opened?
What is the recommended handling procedure for propofol after it has been opened?
Signup and view all the answers
What does the minimum alveolar concentration (MAC) refer to in inhalation anesthetics?
What does the minimum alveolar concentration (MAC) refer to in inhalation anesthetics?
Signup and view all the answers
Which injectable anesthetic is typically used in combination with tranquilizers and opioids for general anesthesia?
Which injectable anesthetic is typically used in combination with tranquilizers and opioids for general anesthesia?
Signup and view all the answers
Inhalation anesthetics primarily exert their effects on which part of the body?
Inhalation anesthetics primarily exert their effects on which part of the body?
Signup and view all the answers
What is a key indication for the use of guaifenesin in an anesthetic protocol?
What is a key indication for the use of guaifenesin in an anesthetic protocol?
Signup and view all the answers
What effects can alpha2-agonists cause at the dosing level?
What effects can alpha2-agonists cause at the dosing level?
Signup and view all the answers
When administering alpha2-agonists, which patient population should be monitored closely during treatment?
When administering alpha2-agonists, which patient population should be monitored closely during treatment?
Signup and view all the answers
Which of the following is a potential effect of alpha2-agonists in animals?
Which of the following is a potential effect of alpha2-agonists in animals?
Signup and view all the answers
What adverse cardiovascular effect is commonly associated with alpha2-agonist usage?
What adverse cardiovascular effect is commonly associated with alpha2-agonist usage?
Signup and view all the answers
What is an essential precaution when using alpha2-agonists?
What is an essential precaution when using alpha2-agonists?
Signup and view all the answers
Which effect should a veterinarian anticipate from the use of alpha2-agonists?
Which effect should a veterinarian anticipate from the use of alpha2-agonists?
Signup and view all the answers
During recovery from alpha2-agonist use, which of the following is crucial to monitor closely?
During recovery from alpha2-agonist use, which of the following is crucial to monitor closely?
Signup and view all the answers
How do alpha2-agonists interact with the body’s cardiovascular system?
How do alpha2-agonists interact with the body’s cardiovascular system?
Signup and view all the answers
In what context should alpha2-agonists be used with caution?
In what context should alpha2-agonists be used with caution?
Signup and view all the answers
Study Notes
Controlled Substance Regulations
- DEA - U.S.: Responsible for enforcing regulations
- CDSA - Canada: Canadian government agency for controlled substances
- RCMP - Canada: Canadian law enforcement agency involved in enforcing regulations
Controlled Substances Recordkeeping
- Two-year inventory in veterinary practice
- Controlled substances log required for monitoring use.
Ordering Controlled Substances
- Schedule II drugs: Ordered using DEA Form 222 for careful tracking.
- Schedule III and IV drugs: Special order forms not required.
Secure Storage of Controlled Substances
- Schedule II to V drugs: Stored in a securely locked, well-constructed cabinet.
- Opioid agonists and antagonists: Stored in a safe or steel cabinet.
- Report significant loss or suspected theft: Within one business day to the DEA and local police.
Precautions for Prescribing Controlled Substances
- Securely store prescription pads.
- Prevent illegal alteration of prescriptions.
Preanesthetic Medications
- Calm or sedate an excited animal.
- Minimize adverse drug effects.
- Reduce the dose of concurrent drugs.
- Ensure smoother anesthetic induction and recovery.
- Provide analgesia.
- Relax muscles.
Anxiolytics
- Minimize stress, anxiety, and fear.
- Gabapentin (mostly cats): Analgesic properties, especially for neuropathic pain. Provides anxiolysis similar to tranquilizers in dogs and cats.
- Trazodone (mostly dogs): Reduces stress, fear, and anxiety.
Preanesthetic Anticholinergics
- Parasympatholytic drugs that block acetylcholine.
- Prevent and treat bradycardia.
- Decrease salivary secretions.
-
Atropine and glycopyrrolate (dogs and cats): Can be administered intravenously, intramuscularly, subcutaneously, or intratracheally.
- Atropine: Faster onset, shorter peak, and shorter duration.
- Glycopyrrolate: Slower onset, longer peak, and longer duration.
Anticholinergic Effects
- Central nervous system: Limited effect.
- Cardiovascular: Prevents bradycardia.
- Respiratory and salivary secretions: Decreased.
- Bronchodilation: Occurs.
- Eye: Mydriasis and corneal drying.
- Gastrointestinal and lacrimal secretions: Decreased.
Anticholinergic Adverse Effects
- Cardiac arrhythmia: Is a contraindication in animals with elevated heart rates or cardiac diseases.
- Temporary bradycardia: Can occur with the use of atropine.
- Thickened respiratory and salivary secretions: May lead to airway blockage, especially in cats and ruminants.
- Intestinal peristalsis inhibition: May lead to colic in horses or bloat in ruminants.
Tranquilizers and Sedatives
- Tranquilizer: Reduces anxiety but not awareness or wakefulness.
- Sedative: Reduces mental activity and causes sleepiness.
-
Three classes used in veterinary medicine:
- Phenothiazines
- Benzodiazepines
- Alpha2-adrenoceptor agonists
General Risks of Tranquilizers and Sedatives
- Never leave a sedated patient unattended due to potential fall risk.
- Sedatives can cause respiratory distress.
- Animals may exhibit unusual behavior when sedated, including aggression.
Phenothiazines: Acepromazine Maleate
- Also known as acepromazine or “ace.”
- Typically used as an anesthetic adjunct.
- Usually administered intravenously or intramuscularly.
Effects and Adverse Effects of Phenothiazines
- Calming/sedation.
- Tachycardia or bradycardia.
- Antiarrhythmic effects.
- Peripheral vasodilation.
- Hypotension.
- Antiemetic.
- Hypothermia.
- Penile prolapse in large animals.
- Decreased packed cell volume (PCV).
Acepromazine Use
- Dose and needle placement: Important to consider.
- Increased potency and duration: Seen in geriatric, neonates, and debilitated animals.
-
Breed considerations:
- Australian Shepherds, Collies: Use low doses.
- Giant breeds, Boxers, Greyhounds: Increased sensitivity.
- Terriers and cats: Resistance.
- Overdose Treatment: Must be considered.
Benzodiazepines
- Minor tranquilizers (controlled substances): Diazepam, Zolazepam, Midazolam
- Rapid onset of action.
- Short duration of action.
- May produce the opposite effect in young, healthy animals.
Effects and Adverse Effects of Benzodiazepines
- Calming and antianxiety in old or ill patients.
- Anticonvulsant.
- Disorientation and excitement in young dogs.
- Dysphoria/aggression in cats.
- Muscle fasciculations in horses.
- Ataxia or recumbency in large animals.
- Few cardiopulmonary effects.
- Skeletal muscle relaxation.
- Diazepam: IM injections may be painful.
Alpha2-Adrenoceptor Agonists
- Also written alpha2-agonists or 2-agonists.
- Noncontrolled agents.
- Produce sedation, analgesia, and muscle relaxation.
- Administered intravenously or intramuscularly.
- Used before minor procedures.
- Readily reversed with an alpha2-antagonist.
Effects and Adverse Effects of Alpha2-Agonists
- Dose-dependent sedation.
- Analgesia.
- Agitation or aggression.
- Reaction to loud noises.
- Muscle tremors in horses.
- Cattle may lie down.
- Initial hypertension, bradycardia, pale mucous membranes; then hypotension, decreased output, decreased heart rate.
- Severely decreased heart rate, blood pressure, cardiac output, tissue perfusion.
- Respiratory depression (can be severe).
- Muscle relaxation.
- Vomiting (in cats and dogs).
- Adverse GI effects: Bloat, colic.
- Hyperglycemia.
- Hypothermia.
- Increased urination.
- Premature parturition (cattle).
- Sweating (horses).
Use of Alpha2-Agonists
- Use with caution and monitor patients closely.
- Avoid using in geriatric, diabetic, pregnant, pediatric, or ill patients.
- Administer anticholinergics 10 to 20 minutes before.
Alpha2-Antagonists
-
Reverse all effects of alpha2-agonists:
- Beneficial effects: Analgesia and sedation.
- Detrimental effects: Bradycardia.
- Wide margin of safety.
-
Effects of overdose:
- Neurological: Excitement and muscle tremors.
- Cardiovascular: Hypotension and tachycardia.
- Gastrointestinal: Salivation and diarrhea.
Opioids
- Produce analgesia and sedation.
- Induce anesthetic with other drugs.
- Classified as agonists, partial agonists, agonist-antagonists, and antagonists.
- Most are controlled substances.
- Administered via multiple routes : IV, IM, SC, Oral, Rectal, Transdermal, Subarachnoid, Epidural.
- Wide margin of safety.
Commonly Used Opioids
- Agonists: Morphine, Hydromorphone, Methadone, Oxymorphone, Fentanyl, and Meperidine.
- Partial agonist: Buprenorphine
- Agonist-antagonists: Butorphanol and Nalbuphine.
- Antagonists: Naloxone
Opioids: Pharmacodynamics
- Mimic endogenous opioid peptides: Beta-Endorphins, Dynorphins, Enkephalins.
- Analgesia and sedative effects: Result from action on receptors in the brain and spinal cord. - Types of receptors: Mu (μ), kappa (κ), and delta (δ), plus many subtypes. Each opioid has a different action at each receptor.
- Agonists: Bind to and stimulate mu and kappa receptors. Best for moderate to severe pain.
- Partial agonists: Bind to and partially stimulate receptors.
- Agonist-antagonists: Bind to mu and kappa receptors, but only stimulate kappa receptors.
- Antagonists: Bind to mu and kappa receptors, but don't stimulate them.
Effects and Adverse Effects of Opioids
- CNS depression or excitement: Depends on dose, route, agent used, species, temperament, and pain level.
- Excellent somatic and visceral analgesia.
- Dose-dependent bradycardia and respiratory depression.
- Panting (dogs).
- Hypothermia (dogs) or hyperthermia (cats).
- Salivation/vomiting (small animals).
- Initial vomiting, diarrhea, and flatulence, then constipation.
- Colic and sweating (horses).
- Increased responsiveness to noise.
- Miosis (dogs), mydriasis (cats and large animals).
- Decreased urine production and urine retention.
Use of Opioids:
- Preanesthetic: Can be used alone or in combination with tranquilizers and anticholinergics.
- Analgesia: Prevents and treats postoperative pain. Can be used with a tranquilizer to produce neuroleptanalgesia.
Neuroleptanalgesia
- A profound state of sedation and analgesia: Induced by simultaneous administration of an opioid and a tranquilizer.
- Wide margin of safety when properly administered:
- Provides sedation for minor procedures.
-
Induces general anesthesia in dogs:
- Not in young, healthy dogs.
- Not in cats.
Opioid Antagonists
-
Reverse undesirable effects of opioids:
- Central nervous system depression and respiratory depression.
- Wake up patient following sedation.
-
Naloxone hydrochloride:
- Intramuscular or slow intravenous administration: Used in dogs, horses, cats, and exotic mammals.
-
Naltrexone:
- Used in wild animals.
- Longer-lasting effect.
Effects of Opioid Antagonists
- Reverses the effects of opioid agonists, partial agonists, and agonist-antagonists.
- Reversal can be complete within a few minutes.
-
Adverse effects are rare:
- Sudden analgesia loss: May cause excitement, anxiety, and sympathetic nervous system stimulation. Prevention through using an agonist-antagonist.
Use of Opioid Antagonists
- Emergencies for opioid reversal.
- Overdose for opioid reversal.
- Reverse neuroleptanalgesia.
-
Reviving neonates delivered by C-section:
- If dam received opioids
- One drop placed under the tongue
Maintenance:
- How fast will the anesthetic depth change in response to changes in the vaporizer setting?
Recovery:
- How long will the patient sleep after anesthesia?
Minimum Alveolar Concentration (MAC)
- Measure of the potency of a drug that determines the average vaporizer setting needed for surgical anesthesia.
- The lower the MAC: The more potent the anesthetic agent and the lower the vaporizer setting.
- Factors that can alter MAC: Age, metabolic activity, body temperature, disease, pregnancy, obesity, and other agents present.
- Individual monitoring: Essential for every patient
Halogenated Organic Compounds: Isoflurane
- Approved for use in dogs and horses: Commonly used in other species.
- Most commonly used inhalant agent in North America.
Physical and Chemical Properties of Isoflurane
- High vapor pressure: Precision vaporizer needed.
- Low blood: gas partition coefficient: Rapid induction and recovery.
- Good for induction with mask or chamber.
- MAC = 1.30% to 1.63%: Helps determine initial vaporizer setting.
- Low rubber solubility.
- Stable at room temperature: No preservatives needed.
- Maintains cardiac output, heart rate, and rhythm: Fewest adverse cardiovascular effects.
- Depresses the respiratory system.
- Maintains cerebral blood flow.
- Almost completely eliminated through the lungs.
- Induces adequate to good muscle relaxation.
- Provides little to no analgesia after anesthesia.
- Can produce carbon monoxide: When exposed to a desiccated carbon dioxide absorbent.
Halogenated Organic Compounds: Sevoflurane
- High vapor pressure: Precision vaporizer required.
- Blood-gas partition coefficient: Rapid induction and recovery.
- Good for induction with mask or chamber.
- High controllability of anesthesia depth.
- MAC = 2.34% to 2.58%
Halogenated Organic Compounds: Desflurane
- Related to isoflurane.
- Expensive.
- Lowest blood-gas partition coefficient: Very rapid induction and recovery.
- Special precision vaporizer required.
- MAC = 7.2% and 9.8%: Least-potent inhalant agent.
- Eliminated by the lungs.
Halogenated Inhalation Agents : Nitrous Oxide
- Used some in veterinary medicine.
- Gas is at room temperature: No vaporizer required.
- Used with a flowmeter and mixed with O2.
- Reduces MAC by 20% to 30%.
Miscellaneous Anesthetic Adjuncts
-
Doxapram:
- Analeptic agent.
- Non-controlled substance.
- Stimulates respiration and speeds recovery.
- Used in neonate puppies and kittens after C-section.
- Intravenous administration or sublingual drops: For neonates
- Mode of action: Stimulates the central nervous system, including respiratory centers in the brain.
Effects and Adverse Effects of Doxapram:
- Wide margin of safety.
- Can cause hyperventilation, hypertension, arrhythmia.
- Lowers seizure threshold.
- Must be used in the presence of adequate oxygen levels in the brain.
- Can cause central nervous system damage.
Use of Doxapram
- Repeat injections may be necessary.
- Reverses respiratory depression: From inhalant agents and barbiturates.
Injectable Anesthetics
- Injectable anesthetics can produce unconsciousness.
- Injectable anesthetics do not provide analgesia or muscle relaxation.
- Injectable anesthetics must be used with other agents to produce complete effects of general anesthesia.
- Injectable anesthetics are administered intravenously “to effect.”
- Commonly used injectable anesthetics include propofol, etomidate, alfaxalone, and barbiturates.
Propofol
- Propofol is an ultra-short-acting, nonbarbiturate anesthetic.
- Propofol is classified as a Schedule IV drug for anesthetic induction and short-term maintenance.
- Propofol is used in small animals, small ruminants, exotic animals, and neonates of all species.
- Propofol is used as an intravenous bolus and CRI to treat status epilepticus in dogs and cats.
Effects and Adverse Effects of Propofol
- Propofol produces dose-dependent CNS depression ranging from sedation to general anesthesia
- Propofol can cause transient excitement and muscle tremors during induction.
- Propofol causes bradycardia, decreased cardiac output, hypotension, respiratory depression, and apnea.
- Propofol can also cause prolonged apnea, decreased oxygen saturation, cyanosis, and muscle relaxation.
- Propofol has an antiemetic effect, decreases intracranial and intraocular pressure, and can cause pain on IV injection.
Propofol Handling and Storage
- Propofol should be shaken thoroughly before use.
- Propofol has poor storage characteristics due to bacterial growth caused by egg lecithin, glycerol, and soybean oil.
- Aseptic technique should be used when handling propofol.
- Discard unused propofol within 6 hours of opening.
- Unopened propofol has a 3-year shelf life.
Alfaxalone
- Alfaxalone is short-acting and has a wide margin of safety.
- Alfaxalone is administered intravenously for induction anesthesia and maintenance.
- Alfaxalone is administered intramuscularly in cats for deep sedation or light anesthesia.
- Alfaxalone is classified as a Schedule IV controlled substance in the United States.
- Alfaxalone is a steroid molecule that functions similarly to other hypnotics.
Effects and Adverse Effects of Alfaxalone
- Alfaxalone produces dose-dependent CNS depression.
- Alfaxalone causes minimal cardiovascular depression.
- Alfaxalone can cause tachycardia and hypotension.
- Alfaxalone can cause respiratory depression, including apnea.
- Alfaxalone causes muscle relaxation.
- Alfaxalone can cause excitement during recovery.
Etomidate
- Etomidate is administered only intravenously.
- Start by administering ¼ to ½ the calculated dose of etomidate.
- The most common adverse effect of etomidate is vomiting.
- Muscle contractions can be minimized with premedication.
- Etomidate can be administered in repeated boluses for short-term anesthesia.
Barbiturates
- Barbiturates are a large class of controlled drugs.
- The use of barbiturates as general anesthetics has declined due to new drug development.
- Short-acting pentobarbital sodium is used to induce and maintain general anesthesia in lab animals, treat status epilepticus in small animals, and is an euthanasia agent.
- Long-acting phenobarbital is often used for seizure control and occasionally as a sedative in dogs and cats.
Dissociative Anesthetics
- Ketamine is the only dissociative anesthetic used in veterinary medicine.
- Ketamine can be used alone in cats for minor procedures or to facilitate restraint.
- Ketamine can be used with other drugs, such as tranquilizers and opioids, to induce general anesthesia.
- Ketamine can be administered as a subanesthetic dose as a CRI for analgesia.
Actions and Effects of Dissociative Anesthetics
- Dissociative anesthetics disrupt nerve transmission in some brain sections.
- Dissociative anesthetics cause selective stimulation in parts of the brain.
- Dissociative anesthetics decrease windup through NMDA inhibition.
- Dissociative anesthetics produce a trancelike state where the animal appears awake but immobile and unaware of its surroundings.
- Dissociative anesthetics are metabolized in the liver or excreted unchanged in the urine.
Effects and Adverse Effects of Dissociative Anesthetics
- Dissociative anesthetics produce a cataleptoid state with intact reflexes.
- Dissociative anesthetics cause open eyes with central and dilated pupils.
- Dissociative anesthetics cause normal or increased muscle tone.
- Dissociative anesthetics cause analgesia, particularly for somatic pain.
- Dissociative anesthetics can cause increased sensitivity to stimuli.
- Dissociative anesthetics can cause nystagmus.
- Dissociative anesthetics cause increased heart rate, cardiac output, and mean arterial pressure.
- Dissociative anesthetics can cause decreased inotropy, apneustic respiration at higher doses, increased salivary and respiratory tract secretions, and pain after IM injection.
Use of Dissociative Anesthetics
- Dissociative anesthetics are administered intramuscularly or intravenously.
- Dissociative anesthetics have a wide margin of safety.
- Dissociative anesthetics are particularly useful in cats and horses.
- Dissociative anesthetics are frequently used in combination with tranquilizers for short procedures, anesthetic induction for intubation, chemical restraint in cats, immobilization of large and exotic animals, and for pain control.
- There is no effective reversal agent for dissociative anesthetics.
Dissociative Anesthetic: Use of Guaifenesin
- Guaifenesin is often used with ketamine in an anesthetic induction protocol.
- Premedication with an alpha2-agonist or acepromazine is advised when using guaifenesin.
- The "triple drip" combination of guaifenesin (GG), ketamine, and xylazine is useful for maintaining anesthesia in horses for less than an hour.
- Guaifenesin is administered intravenously rapidly until the animal is ataxic after premedication.
- Guaifenesin helps to provide a smooth recovery.
Use of Guaifenesin with Dissociative Anesthetics
- Guaifenesin is a component of anesthetic induction protocols in combination with ketamine.
- Premedication is essential when using guaifenesin because it may cause excitement or an increased risk of side effects if not premedicated.
- Guaifenesin is not used as a sole anesthetic agent because its sedation and analgesia are inadequate for surgery.
Inhalation Anesthetics
- Common inhalation anesthetic agents include isoflurane, sevoflurane (halogenated compounds), nitrous oxide, desflurane, enflurane (no longer used in veterinary medicine), halothane (no longer available), and methoxyflurane (no longer available).
Inhalant Anesthetics: Halogenated Organic Compounds
- Isoflurane and sevoflurane are the most commonly used halogenated organic compounds.
- The halogenated organic compounds are liquids at room temperature.
- Halogenated anesthetic agents are stored in a vaporizer on an anesthetic machine.
- The halogenated organic compounds are vaporized in oxygen that flows through the vaporizer.
Halogenated Organic Compounds: Mode of Action and Pharmacology
- Liquid anesthetic is vaporized and mixed with oxygen gas.
- The gas mixture is delivered to the patient via a mask or endotracheal tube.
- The gas mixture travels to the lungs (alveoli), and diffuses into the bloodstream.
- The diffusion rate is dependent on the concentration gradient and lipid solubility.
- The concentration gradient is greatest during the initial induction phase.
- Distribution into the tissues is dependent on blood supply with lipid solubility determining entry into tissues through cell walls.
- The depth of anesthesia is dependent on the partial pressure of the anesthetic in the brain.
- The partial pressure in the brain is dependent on the partial pressure of the anesthetic in the blood and alveoli.
- Maintenance of anesthesia is dependent on sufficient quantities of anesthetic delivered to the lungs.
Effects and Adverse Effects of Halogenated Inhalation Anesthetics
- Halogenated anesthetics cause dose-related CNS depression, hypothermia, and paddling, excitement, and muscle fasciculations during recovery.
- The effects of halogenated anesthetics on heart rate are variable, but they can cause vasodilation and hypotension, decreased cardiac output, and decreased tissue perfusion.
- Halogenated anesthetics cause dose-related respiratory depression with potential hypoventilation, retention of carbon dioxide, and respiratory arrest.
- Halogenated anesthetics provide adequate to good muscle relaxation.
- Halogenated anesthetics can cause depression of respiration in neonates.
- Halogenated anesthetics can produce carbon monoxide when exposed to desiccated CO2 absorbent.
Inhalant Anesthetics: Physical and Chemical Properties
- Inhalant anesthetics have important physical and chemical properties including vapor pressure, partition coefficient, minimum alveolar concentration (MAC), and rubber solubility.
Vapor Pressure
- Vapor pressure is the tendency of an inhalation anesthetic to vaporize into its gaseous state.
- Vapor pressure determines how readily an inhalation anesthetic will evaporate in the anesthetic machine vaporizer.
- Vapor pressure is dependent on temperature and the anesthetic agent.
Vapor Pressure (Volatile vs Nonvolatile Agents )
- Volatile agents have a high vapor pressure.
- Examples of volatile anesthetics include isoflurane, sevoflurane, desflurane, and halothane.
- Volatile anesthetics are delivered from a precision vaporizer to control delivery concentration.
- All precision vaporizers are made to deliver only one specific halogenated agent.
- Nonvolatile agents have a low vapor pressure.
- Nonvolatile agents are delivered from a nonprecision vaporizer.
Blood-Gas Partition Coefficient
- The blood-gas partition coefficient measures the solubility of an inhalation anesthetic in blood compared to alveolar gas (air).
- The blood-gas partition coefficient indicates the speed of induction and recovery for an inhalation anesthetic agent.
- A low blood-gas partition coefficient indicates the agent is more soluble in alveolar gas than in blood at equilibrium.
- A low blood-gas partition coefficient means the agent is less soluble in blood and causes faster induction and recovery.
- A high blood-gas partition coefficient indicates the agent is more soluble in blood than in alveolar gas at equilibrium.
- A high blood-gas partition coefficient means the agent is less soluble in alveolar gas, is absorbed into blood and tissues (sponge effect), and causes slower induction and recovery.
Blood-Gas Partition Coefficient and Clinical Use
- The blood-gas partition coefficient determines the clinical use of an anesthetic agent because it affects induction and recovery time, as well as how readily a mask can be used.
Minimum Alveolar Concentration (MAC)
- MAC is the minimum alveolar concentration of an inhalation anesthetic that prevents movement in 50% of patients in response to a painful stimulus.
- MAC is helpful in determining anesthetic potency.
- A high MAC is associated with low potency.
- A low MAC is associated with high potency.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Test your knowledge on the intricacies of veterinary anesthesia, focusing on factors such as MAC and anesthetic potency. The quiz covers key anesthetic agents like Isoflurane and Doxapram, their effects, and crucial monitoring considerations during procedures. Perfect for veterinary students and professionals seeking to deepen their understanding.
