Anesthetic Problems and Emergencies PDF

Chapter 13 Anesthetic Problems and Emergencies Anesthesia and Analgesia for Veterinary Technicians and Nurses, 6th ed. Thomas and Lerche Learning Objectives—Lesson 13.1 1. List the most common reasons that anesthetic emergencies occur, including problems arising from in...

Chapter 13 Anesthetic Problems and Emergencies Anesthesia and Analgesia for Veterinary Technicians and Nurses, 6th ed. Thomas and Lerche Learning Objectives—Lesson 13.1 1. List the most common reasons that anesthetic emergencies occur, including problems arising from increased patient risk, human error, equipment failure, and the adverse effects of anesthetic agents. 2. Explain how anesthesia of pediatric and geriatric patients differs from anesthesia of healthy adult dogs and cats. 3. Describe the problems involved in anesthetizing each of the following: obese animals; brachycephalic dogs; sighthounds; and patients affected by trauma or cardiovascular, respiratory, hepatic, or renal disease.  Causes of Anesthetic Problems  Human error  Equipment-related issues  Adverse effects of anesthetic agents  Increased patient risk  Anesthetic Problems and Emergencies: Human Error  Inadequate training  Lack of familiarity with equipment or agents  Failure to adequately prepare the patient  Drug calculation and administration errors  Errors caused by fatigue, haste, or inattention  Anesthetic Problems and Emergencies: Equipment Issues (1 of 2)  Equipment failure  Carbon dioxide absorbent exhaustion (rebreathing system)  Failure of oxygen supply  Endotracheal tube (ET) blockage  Anesthetic Problems and Emergencies: Equipment Issues (2 of 2)  Vaporizer problems  Using the wrong anesthetic agent  Vaporizer is overfilled  Tipping the vaporizer  Vaporizer dial becomes stuck or jammed  Two vaporizers used at the same time  Adjustable pressure limiting (APL) valve problems  Leaving the APL valve in a closed position Reducing the Adverse Effects of Anesthetic Agents  Choose a protocol suitable for the condition or needs of the patient  Be familiar with side effects and contraindications for preanesthetic and general anesthesia agents  Multidrug protocols are safer than single drug protocols  Anesthetic Problems and Emergencies: High-Risk Patients  Neonates  Geriatric animals  Brachycephalic dogs  Sighthounds  Obese animals  Cesarean deliveries  Trauma victims  Cardiac issues  Chronic disease  High-Risk Patients: Neonates (1 of 2)  Neonates and pediatric animals are less than 3 months old  Preoperative fasting can cause hypoglycemia and dehydration: water should not be withheld  Intravenous isotonic, crystalloid solution with 5% dextrose during anesthesia  Use pediatric fluid infusion pump or syringe pump at 60 drops/mL  Use pediatric or gram scale to weigh animals less than 5 kg  Injectable agents may require dilution  High-Risk Patients: Neonates (2 of 2)  Monitor dose closely due to plasma protein binding of drugs and inefficient metabolism within the liver  Inefficient renal function  Inhalants commonly used in neonates and prenates  Increased risk for hypothermia, hypotension, hypoxemia  Endotracheal tube may need to be shortened  High-Risk Patients: Geriatric Animals  Have reached 75% of life expectancy  Decreased heart, lung, and liver function  Presence of degenerative disorders  Poor response to stress  Reduced anesthetic requirements  Prolonged recovery  Tendency for hypothermia  High-Risk Patients: Obese Animals  Anesthetics are not efficiently distributed to fat stores  Lower doses per kilogram required in dogs  May have respiratory issues  Hypercapnia may result from rapid shallow respirations  High-Risk Patients: Brachycephalic Animals  Avoid agents that depress respiration or relax muscles of the pharynx/larynx  Prone to bradycardia  Difficult induction period; preoxygenate if possible  Difficult to intubate  Use laryngoscope and smaller diameter tube  Use agents that allow rapid recovery  Monitor closely during recovery for dyspnea  Recover in an excitement-free or stress-free environment  Postoperative tranquilizers may be needed  High-Risk Patients: Sighthounds  Increased sensitivity to some anesthetic agents  High-Risk Patients: Cardiovascular Disease  Anemia, shock, cardiomyopathy, congestive heart disease  Preanesthetic evaluation, laboratory evaluation, and evaluation of heart rate and synchrony with the pulse are part of the cardiovascular evaluation  Most common problem is bradycardia  High-Risk Patients: Respiratory Disease (1 of 2)  Delay if possible until respiratory function is improved  Avoid use of NO2  Sigh the patient every 5 to 10 minutes to reduce these issues of hypoventilation, atelectasis, and/or apnea  Oxygen-carrying capabilities should be assessed by PCV  O2 saturation evaluated with a pulse oximeter or blood gas analysis  High-Risk Patients: Respiratory Disease (2 of 2)  Evaluate patient for  Dyspnea or cyanosis  Examine for  Respiratory character  Depth of anesthesia  Correct placement of the endotracheal tube  Occlusion of the endotracheal tube  Oxygen saturation  Arterial or end-tidal CO2  High-Risk Patients: Hepatic Disease  Liver is necessary for drug metabolism, blood clotting factors, plasma proteins, carbohydrate metabolism  Preanesthetic agents must be chosen with care  Avoid use of ketamine and diazepam  High-Risk Patients: Renal Disease  Kidneys maintain volume and electrolyte composition of body fluids  Renal excretion removes anesthetic agents and metabolites from the body  General anesthesia is associated with decreased blood flow to the kidneys  Correct dehydration before anesthesia  Animals with renal disease may have prolonged recovery when conventional doses are used  High-Risk Patients: Cesarean Delivery (1 of 4)  Most often an emergency surgical procedure  Patient is in compromised condition due to advanced pregnancy  Patient is not properly prepared for surgery (e.g., not fasted)  Most anesthetic agents will cross the placenta and affect fetuses  Patient is at risk for going into shock during surgery  High-Risk Patients: Cesarean Delivery (2 of 4)  Unique risks  Aspiration of vomitus  Decreased lung capacity  Increased cardiac load  Physiologic anemia  Poor regulation of blood pressure  Decreased anesthetic requirements  All drugs readily cross the placenta  Hemorrhage is common  Increased risk of shock  High-Risk Patients: Cesarean Delivery (3 of 4)  Anesthesia protocols  Epidural with tranquilizers or neuroleptanalgesic  General anesthesia with injectable or inhalant agents  Opioid agents  Reversible in both mother and neonate  High-Risk Patients: Cesarean Delivery (4 of 4)  Anesthetic concerns  Hypoxemia  Hypercarbia  Hypotension  Physiological anemia  Acid-base imbalance  Tissue trauma  Cardiac arrhythmias  Care of Puppies and Kittens Delivered by Cesarean Section (1 of 2)  Respiratory function  Deliver oxygen by facemask  Intubate with 16- or 18-gauge IV catheter and gently bag every 5 seconds  Aspirate fluid from the mouth and nose with eyedropper or bulb syringe  Administer reversal agents, doxapram, and/or dilute atropine as needed  Care of Puppies and Kittens Delivered by Cesarean Section (2 of 2)  Cardiac function  Gentle cardiac massage  Deliver oxygen by facemask  Allow to nurse as soon as mother is recovered  Watch neonates if mother is still groggy  Anesthetic agents secreted in milk don’t affect neonates  High-Risk Patients: Trauma Patients  Recent trauma that requires emergency attention  Increases anesthetic risk  Respiratory difficulties are common  Stabilize before anesthesia  Allows more complete assessment of injury  Stabilization reduces anesthetic risk  Trauma Patients: Diaphragmatic Hernia  Common surgery to animals in respiratory distress  Preoxygenation advised for 5 to 10 minutes prior to surgery  Avoid head-down position  Injectable agent preferred over mask induction  Be prepared to assist in the control of ventilation  Closely monitor for cyanosis  Observe closely during recovery  Learning Objectives—Lesson 13.2 (1 of 2) 4. Describe the role of the veterinary technician or nurse in responding to anesthetic emergencies. 5. List common causes of and responses to the following anesthetic problems: inadequate anesthetic depth, excessive anesthetic depth, pale mucous membranes, prolonged capillary refill time, and hypotension. 6. List common causes of and responses to the following anesthetic problems: cyanosis and dyspnea, tachypnea, apnea, respiratory arrest, abnormalities in cardiac rate and rhythm, and cardiac arrest.  Learning Objectives—Lesson 13.2 (2 of 2) 7. Explain the principles of cardiopulmonary resuscitation as recommended in the RECOVER Guidelines, including basic life support and advanced life support. 8. List the most common problems that may arise in the recovery period and the appropriate action that can be taken to prevent or treat these problems.  Anesthetic Problems and Emergencies: General  Role of the Veterinary Technician  Active role in resuscitation  Advised to roleplay emergency situations with full staff  Emergency, after-hour care in the absence of the veterinarian allowed in most states and provinces  Responding to an Emergency  Think before acting  Crash cart supplied and ready  Drug list and supplies up to date  Do no harm  Post-emergency follow up discussion  Common Emergencies During Anesthesia  Animals that will not stay anesthetized  Animals that are too deeply anesthetized  Pale mucous membranes  Prolonged capillary refill time  Hypotension  Dyspnea and/or cyanosis  Tachypnea  Abnormalities in cardiac rate and rhythm  Apnea  Respiratory arrest  Cardiac arrest  Animals That Will Not Stay Anesthetized  An inadequate vaporizer setting  A vaporizer inadequately filled with liquid anesthetic  A blocked, misplaced, or disconnected endotracheal tube  An endotracheal tube too small or inadequately cuffed  Apnea or inadequate tidal volume  Misassembly or leakage of the anesthetic machine  Inadequate oxygen flow  Malfunction or incorrect calibration of the vaporizer  Responding to Inadequate Anesthetic Depth (1 of 2)  Check that the vaporizer setting is appropriate and adjust it accordingly  Check that the vaporizer contains an adequate amount of liquid anesthetic and fill it if necessary  Confirm that the endotracheal tube is not blocked, is in the trachea, and that the breathing circuit is attached  Check that air is not leaking around the endotracheal tube  Responding to Inadequate Anesthetic Depth (2 of 2)  Check that the patient is breathing and that chest excursions are adequate  Check that oxygen flow is adequate  Re-check the patient’s monitoring parameters  If none of the previously listed causes are identified, switch the patient to another machine  Animals That Are Too Deeply Anesthetized (1 of 2)  A respiratory rate of 6 breaths/min or fewer; shallow respirations or exaggerated respiratory movements  Pale or cyanotic mucous membranes  Capillary refill time greater than 2 seconds  Bradycardia  Weak pulse  Hypotension (systolic blood pressure less than 80 to 90 mm Hg)  Cardiac arrhythmias  Animals That Are Too Deeply Anesthetized (2 of 2)  Cold extremities; body temperature is often less than 35° C  Absent reflexes, including palpebral and corneal reflexes  Flaccid muscle tone  Dilated pupils; absent pupillary light reflex  Responding to Excessive Anesthetic Depth  Immediately decrease the vaporizer setting and inform the veterinarian  If warranted, begin to ventilate the animal with pure oxygen  Use of intravenous fluids, external heat, and specific reversing agents (such as yohimbine, atipamezole, or naloxone) may be advised  Safest to assume that the animal’s anesthetic depth is too deep and to decrease the vaporizer setting while observing the animal carefully for signs of arousal  Pale Mucous Membranes  Causes:  Preexisting conditions  Blood loss during surgery  Anesthetic agent that causes vasodilation and hypotension  Hypothermia  Pain  Treating a Patient with Pale Mucous Membranes  Ascertain the animal’s anesthetic depth  Monitor vital signs including heart rate, respiration, pulse strength, and capillary refill time  Rule out possible causes, including hypothermia, hypotension, drug reactions, and blood loss, and pain  Consult the attending veterinarian  Prolonged Capillary Refill Time (>2 Seconds)  Blood pressure cannot adequately perfuse superficial tissues  May result from conditions present before induction of anesthesia  May be secondary to blood loss during surgery  May be seen in animals in deep anesthesia  Treating Prolonged Capillary Refill Time  Immediately check the animal’s pulse and blood pressure reading (if available)  Roughly estimate the systolic pressure by palpating a peripheral pulse  Closely observe the animal for other signs of shock, including hypothermia and tachycardia (or bradycardia in later stages of shock)  Treatment of Hypotension  Anesthetic depth should be reduced, if possible  Minimal use of vasodilation drugs  Optimize pain control with injectable analgesics  Crystalloid fluids should be administered at rates of 3 to 10 mL/kg/hr in dogs and large animals and 3 to 5 mL/kg/hr in cats  If blood pressure cannot be maintained, colloids may be given in concert with crystalloids  Several drug options to stabilize blood pressure  Keep the patient warm through by supplemental heat  Dyspnea and/or Cyanosis  Causes  The animal is unable to obtain oxygen from the anesthetic machine  The animal is unable to breathe normally  Heavy surgical drapes or constricting bandages are impairing normal respiration  The animal is too deeply anesthetized  Treating Dyspnea and/or Cyanosis  The anesthetist must first ensure that oxygen is being delivered to the patient  Once oxygen flow has been established, the vaporizer should be turned off, and the animal should be bagged with 100% oxygen  Rarely, an emergency tracheostomy will allow the insertion of a breathing tube, if necessary  Administer intravenous fluids or emergency drugs  Close observation during resuscitative efforts for signs of cardiac arrest  Supplemental oxygen should be continued into the recovery period as necessary  Abnormalities in Cardiac Rate and Rhythm  Tachycardia  May result from drug administration  May be a preexisting condition  Not all cases require treatment  Bradycardia  May be secondary to drug administration, vagal stimulation, deep anesthesia, or physiologic imbalances  May not require treatment  Cardiac arrhythmia  Caused by anoxia/hypercarbia, poor tissue perfusion, acid/base imbalance, myocardial damage  Diagnose with ECG; report to veterinarian  Treating Tachypnea  Assess the anesthetic depth  Check the CO2 absorber granules or the capnogram for hypercapnia  If anesthetic depth is inadequate, increase anesthetic administration to bring the patient into an appropriate plane.  If anesthetic depth, body temperature, and vital signs appear to be within acceptable limits, the anesthetist should refrain from changing the vaporizer setting Treatment of Cardiac Arrhythmias  Continuous electrocardiographic monitoring to track the status of the arrhythmia  Rule out inadequate oxygen flow or carbon dioxide accumulation  Increase ventilation by periodic intermittent manual ventilation bagging or use of a ventilator  Antiarrhythmic drugs such as atropine or lidocaine (without epinephrine) may be administered on the veterinarian’s orders  Apnea  Temporary cessation of breathing secondary to anesthetic administration, hyperventilation, and a variety of other causes  Occurs following anesthetic induction by intravenous injection, mask, or chamber  Monitor heart rate, mucous membrane color, oxygen saturation, and end-tidal CO2  Patient may not require treatment  Respiratory Arrest  The total cessation of breathing  Causes: period of prolonged apnea, anesthetic overdose, cessation of oxygen flow, and preexisting respiratory disease  Potentially fatal  Warning signs: a slowing respiratory rate, dyspnea, and/or cyanosis (other vital signs are often normal)  Periodic, intermittent, manual ventilation should continue until heart rate, mucous membrane color, and pulse ox values return to normal  Treatment of Respiratory Arrest (1 of 2)  Inform the veterinarian  If the patient is not already intubated, an endotracheal tube should be immediately inserted and the patient connected to an anesthetic machine delivering 100% oxygen  Check the heart rate to ensure that cardiac arrest has not occurred  Turn off the anesthetic vaporizer  Ensure oxygen flow is adequate by checking the tank pressure gauge and flowmeter  Treatment of Respiratory Arrest (2 of 2)  Ensure the airway is not obstructed by bagging the patient and observing that the chest rises when squeezing the bag (during inspiration)  Bag with oxygen at a rate of once every 3 to 5 seconds. Continue bagging until vital signs improve  The veterinarian may advise that doxapram, reversal agents, or other drugs be given.  Ensure that the patient is kept warm  Cardiac Arrest  Cardiac arrest is a cessation of circulation of oxygenated blood to the tissues due to failure of the heart to pump effectively  Follows abnormal electrical cardiac activity  Can occur at any time during general anesthesia  May be preceded or followed by respiratory arrest  Signs are typically evident before the event  Cardiopulmonary Arrest  Cardiac arrest and respiratory arrest often closely follow one another  Once arrest occurs, permanent brain damage may result if oxygen delivery to the brain is not reestablished within approximately 5 minutes  Coordinated action by all hospital staff members is essential to reverse cardiopulmonary arrest  Cardiopulmonary Resuscitation in Veterinary Species  RECOVER initiative (Reassess Campaign on Veterinary Resuscitation)  Guidelines differ from traditional CPR  All personnel must be competently prepared for an event of CPA  Challenging to do alone – 3 to 5 staff members are ideal  Cardiopulmonary Resuscitation in Veterinary Species – Terminology  Terms to know  BLS Basic Life Support  ALS Advanced Life Support  ROSC Return of Spontaneous Circulation  PAC Post-Arrest Care  Basic Life Support (1 of 3)  In a nonresponsive patient  FIRST quickly (5 to 10 seconds) determine whether the animal has arrested  Chest compressions should begin  Followed by endotracheal intubation and manual ventilation  Basic Life Support (2 of 3)  STEP #1 Chest Compressions  High-quality chest compressions  Patient placed on its right or left side with feet away from care-giver  Two-handed technique over the widest part of the chest  Compressions 100 to 120 bpm  Compress 1/2 to 1/3 of the chest width, allowing the chest to re-expand between compressions  Alternate method: Interposed abdominal compressions  Basic Life Support (3 of 3)  STEP #2 Intubation and Ventilation  In combination with chest compressions, ventilation support must be provided Endotracheal intubation  Lateral recumbency, ventilate with 100% oxygen  10 breaths per minute  Tidal volume of 10 mL/kg Mouth to mouth  Following 30 chest compressions  Two quick breaths  Compressions do NOT stop when breaths are given  Advanced Life Support (1 of 6)  STEP #3 ECG and End-Tidal CO2 Monitoring  Place ECG leads (do not stop compressions)  DO NOT USE ALCOHOL (use physiologic saline solution)  Monitor the quality of chest compressions with a capnograph  Advanced Life Support (2 of 6)  STEP #4 Obtaining Vascular Access  Place an IV catheter in a peripheral vein  Alternative intraosseous route can be used  If not possible, drugs can be given by the intratracheal route  Intracardiac injections should be avoided if possible  Advanced Life Support (3 of 6)  STEP #5 Administration of Reversal Agents  Administer appropriate reversal agents if sedative or anesthetic drugs given before arrest  Dose according to the CPR Emergency Drugs and Doses  Advanced Life Support (4 of 6)  Additional steps  Briefly pause compressions following each 2-minute cycle of BLS  Change compressors  Evaluate patient for ROSC  Evaluate ECG tracing for rhythm diagnosis  Advanced Life Support (5 of 6)  Normalizing the heart rhythm  Therapy appropriate to ECG diagnosis  Treatment of asystole or pulseless electrical activity (PEA)  May be treated with low-dose epinephrine or vasopressin  Advanced Life Support (6 of 6)  Open-chest CPR  When external compressions are not effective  Lateral thorax is clipped and rinsed with alcohol  Self-adhering drape applied  Skin incision made between the 7th & 8th rib  Incision through muscle into chest cavity  Hand is used to firmly pump heart at a rate of 100 times/min  Aftercare  Monitoring is essential  Common for another cardiac arrest within 24 hours  Complex; based on many factors  Many patients cannot be successfully revived Regurgitation During Anesthesia  A passive process under anesthesia  No retching, just fluid draining from animal’s mouth or nose  Stomach contents may be aspirated into respiratory tract  Most common occurrence in head-down surgical positions and in ruminants  Treatment  Immediate placement of cuffed ET tube  Clean out regurgitated material with suction  Vomiting During or After Anesthesia  Common in brachycephalic dogs or nonfasted animals  An active process usually accompanied by retching  Usually occurs as the animal is losing or regaining consciousness  Signs  Airway obstruction leading to dyspnea/cyanosis, bronchospasm  Treatment  Intubation and suction if unconscious  Lower head and clean oral cavity if conscious  Seizures After Anesthesia  Seizures  Seen with ketamine administration, after diagnostic procedures (myelography), or preexisting conditions  Signs  Spontaneous twitching; uncontrolled movements of head, neck, and limbs; opisthotonus; triggered by a stimulus  Treatment  Reduce stimuli, postoperative analgesia, diazepam or propofol, monitor for hyperthermia  Emergence Delirium After Anesthesia  Emergence delirium  Seen after barbiturate anesthesia or high opioid doses, as spontaneous paddling and vocalization  Treatment may not be necessary  Sedatives may help  Naloxone can reverse opioids  Seizures should be differentiated from emergence delirium  Dyspnea in Dogs  Breed-related  Brachycephalic dogs  Airway obstruction  Anatomy, foreign objects, postsurgical tissue swelling  Humidified oxygen can be delivered to an awake animal  By facemask, nasal cannula, E-collar, or oxygen cage/tent  Dyspnea in Cats  Dyspnea caused by laryngospasm sometimes triggered by removal of the ET tube  Laryngeal edema may result from repeated intubation attempts  May breathe with an audible stertor (wheeze) Differentiate from growling during expiration  May resolve or may need oxygen via facemask, intubation, or a tracheotomy  Easier to prevent than treat  Causes of Prolonged Recovery  Impaired renal or hepatic function  Hypothermia  Patient susceptibility to anesthetic agent  Breed variation  Coexisting disorder  Prolonged anesthesia or deep anesthesia