ANESTHETIC PROBLEMS AND EMERGENCIES CHAPTER 12 Every anesthetic procedure has the potential to cause death of the animal

Emergencies are uncommon and the overwhelming majority of patients recover from anesthesia with no ill lasting effects

WHY,WHY,WHY DO ANESTHETIC PROBLEMS AND EMERGENCIES ARISE? 1. HUMAN ERROR!

HUMAN ERROR FAILURE TO OBTAIN AN ADEQUATE HISTORY OR PHYSICAL EXAMINATION ON THE PATIENT. *Ideally, every patient scheduled for anesthesia should have a complete physical examination, and a thorough history should be obtained with the owner present. Less than ideal circumstances are common: Owner drops patient off in a hurry Patient brought in by neighbor or friend Receptionist takes the history Physical exam is cursory or omitted HISTORY? PHYSICAL?

HUMAN ERROR LACK OF FAMILIARITY WITH THE ANESTHETIC MACHINE OR DRUGS USED The confident, knowledgeable, experienced RVT! The not so confident kennel worker who was asked to assist in surgery today.

HUMAN ERROR INCORRECT ADMINISTRATION OF DRUGS INACCURATE WEIGHT MATHEMATICAL ERRORS USE OF WRONG MEDICATION *Be aware of medications that come in different concentrations ADMINISTRATION OF MEDS BY INCORRECT ROUTE *knowledge of pharmacology *drugs with narrow margin of safety CONFUSION BETWEEN SYRINGES *ALWAYS LABEL SYRINGES USE OF INAPPROPRIATE SYRINGE SIZE

HUMAN ERROR PRESSURES AND DISTRACTIONS Feeling hurried or rushed Distraction because of ineffective multi-tasking Fatigue Inattentiveness Be proactive, rather than reactive! Recognize early signs of trouble Pay attention to patient and machines

WHY,WHY,WHY DO ANESTHETIC PROBLEMS AND EMERGENCIES ARISE? 2. EQUIPMENT FAILURE *In many cases the failure of the machine is in fact a failure of the operator.

EQUIPMENT FAILURE CO2 ABSORBER EXHAUSTION *In re-breathing systems, if CO2 is not removed from the circuit, the patient will experience hypercapnia. * In a non re-breathing system, if the gas flow is too low, there may also be a significant re-breathing of expired gases. ↑ CO2 = Tachypnea, tachycardia, brick red mucous membranes, cardiac arrhythmias, respiratory acidosis Human error!

EQUIPMENT FAILURE INSUFFICIENT O2 FLOW You will need to check both the flowmeter and the oxygen tank pressure gauge. Oxygen tank runs out Hose becomes disconnected Obstruction or leak occurs *If the oxygen flow stops while the patient is hooked up to a non re-breathing system, the anesthetist should disconnect the hose from the Endotracheal tube, allowing the patient to breathe room air. If a re-breathing (circle) system is being used, the patient can remain connected for a short period of time, provided the reservoir bag remains inflated. Human Error

EQUIPMENT FAILURE ANESTHETIC MACHINE MISASSEMBLED Take time to learn and follow the direction and path of gas flow within the machine. Every time a connection is added or removed, the anesthetist should ensure that the correct pattern of flow is maintained and that all connections are secure. **Soda-Lyme container main leak

EQUIPMENT FAILURE ENDOTRACHEAL TUBE PROBLEMS BLOCKED TUBES Twisting or kinking of the tube (inappropriate positioning) Accumulation of material such as blood, saliva, excess lubricant Tube advanced too far into a bronchus CHECK TUBE FUNCTION: BAG the patient – watch for chest rising Disconnect the patient – feel for air coming out of the tube when the patient’s chest is compressed If an accumulation of material is causing the obstruction, it may be helpful to suction with a syringe through a red-rubber catheter or feeding tube.

EQUIPMENT FAILURE VAPORIZER PROBLEMS Wrong anesthetic in the vaporizer Vaporizer is empty Do not tip the vaporizer – could result in leakage into the oxygen bypass Vaporizer dial may be jammed Don’t overfill the vaporizer

EQUIPMENT FAILURE POP-OFF VALVE PROBLEMS The pop-off valve is inadvertently left closed Closed pop-off valve →pressure rises in the circuit →reservoir bag expands, as well as the patient’s lungs →exhalation is prevented *This can lead to decreased cardiac output, low blood pressure, and death. If pressure rises in the circuit and the bag is full and tight, the anesthetist should attempt to open the pop-off valve and/or decrease the oxygen flow rate.

WHY,WHY,WHY DO ANESTHETIC PROBLEMS AND EMERGENCIES ARISE? 3. ANESTHETIC AGENTS Every injectable or inhalation agent has the potential to harm a patient and, in some cases, cause death. Review the description of the pharmacologic and physiologic effects of pre-anesthetic and general anesthetic agents in chapters 1 and 3.

WHY,WHY,WHY DO ANESTHETIC PROBLEMS AND EMERGENCIES ARISE? 4. PATIENT FACTORS pre-operative status age concurrent disease breed

PATIENT FACTORS GERIATRIC PATIENTS (75% of life expectancy) POTENTIAL PROBLEMS Reduced organ function- liver, kidney, heart Poor response to stress At risk for degenerative disorders- diabetes, CHF, cancer Increased risk for hypothermia and overhydration Prolonged recovery

Geriatric Patients solutions POTENTIAL SOLUTIONS Reduce anesthetic dosages Increase preanesthetic blood work from mini to a general profile, include u/a, x-rays, ECG if needed Allow a longer time for response to drugs Reduce fluid rate Keep patient warm Choose anesthetic agents with minimal CV effects Pre-oxygenate

PATIENT FACTORS PEDIATRIC PATIENTS (<3 months) POTENTIAL PROBLEMS Increased risk for hypothermia and overhydration Increased risk of hypoglycemia, hypotension, Bradycardia Inefficient excretion of drugs-reduced kidney and liver function Difficult intubation Difficult IV cath placement POTENTIAL SOLUTIONS Be proactive about heat preservation Avoid prolonged fasting (+/- 5% dextrose administration) Reduce anesthetic dosages Use a gram scale to weigh Use inhalant anesthetics

PATIENT FACTORS BRACHYCEPHALIC DOGS POTENTIAL PROBLEMS Conformational tendency toward airway obstruction Elongated soft palate Small nasal openings Hypoplastic trachea Difficult to intubate Abnormally high vagal tone Bradycardia POTENTIAL SOLUTIONS Use an anticholinergic Pre-oxygenate Induce rapidly with IV agents Delay extubation Close monitoring during recovery- recover in a excitement free area

PATIENT FACTORS SIGHTHOUNDS POTENTIAL PROBLEMS POTENTIAL SOLUTIONS Increased sensitivity to barbiturates Lack of body fat for redistribution/elimination of the drug POTENTIAL SOLUTIONS Use alternative agents

PATIENT FACTORS OBESE PATIENTS POTENTIAL PROBLEMS POTENTIAL SOLUTIONS Accurate dosing is difficult- lower dose /kg Poor distribution of drugs Respiratory difficulty- shallow rapid respirations during anesthesia POTENTIAL SOLUTIONS Dose according to ideal weight Pre-oxygenate Induce rapidly Delay extubation Close monitoring during recovery

PATIENT FACTORS CESAREAN PATIENTS- normally an emergency POTENTIAL PROBLEMS DAM: increased workload to heart Respiration compromised Increased risk of hemorrhage- shock/hypotension Increased risk of vomiting/regurgitation- not normally fasted Hypoxemia Hypercarbia Acid/base imbalance Tissue trauma Cardiac arrhythmias OFFSPRING: susceptibility to the effects of the anesthetic agents (reduced Cardio and Respiratory function)

Cesarean patients POTENTIAL SOLUTIONS DAM: IV fluids Clip patient before induction, in lateral recumbency Pre-oxygenate Reduce anesthetic dosages OFFSPRING: use doxapram and/or atropine aspirate fluids from mouth Administer oxygen via face mask, intubate with 18 or 16g IVC Keep warm Encourage nursing

Patient Factors TRAUMA PATIENTS POTENTIAL PROBLEMS POTENTIAL SOLUTIONS Respiratory distress common- decrease in tidal volume, increase in CO2 Cardiac arrhythmias Shock and hemorrhage- hypotension Internal injuries POTENTIAL SOLUTIONS Stabilize patient if possible Obtain chest rads, ECG Check for other concurrent injuries

Anesthetic Problems and Emergencies: Patient Factors Change in blood pressure Resulting from a change in cardiac output or vascular tone Anesthetic depth will affect both parameters Hypotension → decreased tissue perfusion → tissue hypoxia/anoxia → anaerobic glycolysis → lactic acid production → acid/base imbalance Monitor blood pressure closely Doppler or oscillometric methods Digital pulse palpation Capillary refill time

TREATMENT OF HYPOTENSION REDUCE ANESTHETIC DEPTH PRESERVE WARMTH FLUID THERAPY- SHOCK RATE ADMINISTRATION OF EMERGENCY DRUGS: Corticosteroids Sodium bicarbonate Cardiac inotropes (dopamine, dobutamine, ephedrine)

Fluid Therapy for Hypotension Crystalloid fluid administration May have to deliver small boluses for rapid therapy Crystalloid fluids stay in intravascular space <2 hours Watch for fluid overload, especially in cats Monitor heart rate, blood pressure, mucous membrane color, and capillary refill time

Fluid Therapy for Hypotension (Cont’d) Colloid fluid administration Helpful if blood pressure can’t be maintained Remain in the intravascular space longer than crystalloids Will increase colloidal osmotic pressure and help stabilize blood pressure Given in smaller volume in conjunction with crystalloids Hetastarch, Dextran 40 or 70, 10% Pentastarch, plasma, whole blood

Respiratory problems in the trauma patient Direct trauma to the chest leading to lung collapse or failure of alveolar gas exchange Must remove air/fluid from chest cavity prior to anesthesia Deliver supplemental oxygen Oxygen delivery methods Flow-by-oxygen Nasal catheters Oxygen collars

Thoracocentesis (Chest Tap) To relieve pneumothorax or pleural effusion from chest cavity Performed by veterinarian Prepped by veterinary technician Temporary bandage over chest wound Place animal in sternal recumbency or standing position Shave lateral chest wall between the 7th and 9th intercostal spaces caudal to point of the elbow Aseptically prepare 4 cm × 4 cm area Prepare a 20- to 22-gauge, 1- to 1½-inch catheter with a three-way stopcock and large syringe video

PATIENT FACTORS CARDIOVASCULAR DISEASE POTENTIAL PROBLEMS Circulation compromised Pulmonary edema common Increased tendency to develop arrhythmias and tachycardia POTENTIAL SOLUTIONS Alleviate pulmonary edema (diuretics) Pre-oxygenate Avoid agents that may cause arrhythmias Prevent overhydration- cut fluids in 1/2

Preexisting cardiovascular disease Anemia Shock Cardiomyopathy (primary or secondary) Congestive heart disease (mitral valve insufficiency) Heartworm disease Coexisting imbalances (e.g., hypoxia, hypercapnia, electrolyte imbalances)

Bradycardia Most common cardiac anesthetic problem Caused by preanesthetic or anesthetic drugs Force of cardiac contraction may also be decreased Blood return to the heart may be decreased (preload) Treat with drugs or adjustment of anesthetic depth

Cardiac arrhythmias Caused by anoxia/hypercarbia, poor tissue perfusion, acid/base imbalance, myocardial damage Difficult to detect on physical examination; may find dropped beats Diagnose with ECG and report immediately to veterinarian who will determine the treatment required Concurrent pulmonary disease is sometimes seen

PATIENT FACTORS RESPIRATORY DISEASE POTENTIAL PROBLEMS Poor oxygenation of tissues Patient may be anxious and difficult to restrain Increased risk of respiratory arrest POTENTIAL SOLUTIONS Avoid unnecessary handling Pre-oxygenate Induce with injectable agents Intubate rapidly; control ventilation Monitory closely during recovery

Respiratory disease Caused by: Clinical signs Tachypnea Dyspnea Pleural effusion Diaphragmatic hernia Pneumothorax Pneumonia Tracheal collapse Pulmonary edema Clinical signs Tachypnea Dyspnea Cyanosis

Anesthetic considerations VT is reduced and respiratory rate is decreased in most anesthetized animals A decrease in VT will result in a decreased alveolar gas exchange Lighten anesthesia as much as possible in a patient with respiratory disease Provide intermittent ventilation Evaluate oxygen-carrying capacity with PCV or pulse oximeter Preoxygenation is necessary prior to induction

Diaphragmatic Hernia Dysnpnea- pre oxygenate Avoid head down positions Intubate rapidly “bagging” patient Pay close attention to pulse ox, capnograph, and do a arterial blood gas if available.

PATIENT FACTORS HEPATIC DISEASE POTENTIAL PROBLEMS Liver necessary for drug metabolism, blood clotting factors, plasma proteins, carbohydrate metabolism Decreased synthesis of clotting factors Possibly hypoproteinemic Dehydration common Anemic and/or icteric Prolonged recovery POTENTIAL SOLUTIONS Pre-anesthetic blood work Preanesthetic agents must be chosen with care Use inhalant anesthetics Close monitoring during recovery

PATIENT FACTORS RENAL DISEASE POTENTIAL PROBLEMS POTENTIAL SOLUTIONS Delayed excretion of anesthetic agents Electrolyte imbalances common Dehydration may be present POTENTIAL SOLUTIONS Pre-anesthetic blood work Rehydrate before surgery Reduce anesthetic dosages IV fluids

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 Diagnosis: urine specific gravity, BUN, creatinine Offer water up to 1 hour prior to premedication Correct dehydration prior to anesthesia

Anesthetic Problems and Emergencies: Patient Factors (Cont’d) Urinary blockage Clinical signs Depression Dehydration Uremia Acidosis Hyperkalemia (can lead to cardiac arrest) Inhalation agents are less hazardous for the patient

ANESTHETIC PROBLEMS AND EMERGENCIES Anesthetic problems will inevitably occur at some point in your career. No anesthetic experience is the same, so beware of the false sense of security!

ANESTHETIC PROBLEMS AND EMERGENCIES The Role of the Veterinary Technician in Emergency Care

ANIMALS THAT WILL NOT STAY ANESTHETIZED Animals won’t stay anesthetized Check vaporizer setting Check level of anesthetic in the vaporizer Proper ET tube placement or air leakage around it Patient apnea Shallow respirations Proper assembly of anesthetic machine with tight connections Adequate oxygen flow Anesthetic machine/vaporizer is working properly Agonal breathing vs. light plane breathing

ANIMALS THAT ARE TOO DEEPLY ANESTHETIZED Animals are too deeply anesthetized <6 bpm; shallow respirations, dyspnea Pale/cyanotic mucous membranes Capillary refill time >2 seconds Bradycardia Weak pulse; systolic blood pressure <80 mm Hg Cardiac arrhythmias; irregular QRS complexes or VPCs Hypothermia Absent reflexes Flaccid muscle tone Dilated pupils

TREATING EXCESSIVE ANESTHETIC DEPTH ADJUST THE VAPORIZER: NOTIFY THE VETERINARIAN: BAG THE ANIMAL 1. Close the pop-off valve 2. fill the reservoir bag with oxygen 3. gently squeeze the bag until the patient’s chest rises slightly (15-20 cm H2O) 4. Repeat until animal shows signs of recovery

PALE MUCOUS MEMBRANES Pale mucous membranes Preexisting conditions Blood loss during surgery Anesthetic agent that causes vasodilation and hypotension Hypothermia Pain

TREATMENT OF PALE MUCOUS MEMBRANES Ascertain the animal’s anesthetic depth: HR, RR, pulse quality, CRT Consult the veterinarian Fluids, blood transfusion

Anesthetic Problems and Emergencies (Cont’d) Prolonged capillary refill time (>2 seconds) Blood pressure cannot adequately perfuse superficial tissues May result from conditions present prior to induction May be secondary to blood loss during surgery May be seen in animals in deep anesthesia

DYSPNEA AND/OR CYANOSIS DYSPNEA: respiratory difficulty CYANOSIS: bluish coloration of the mucous membranes indicating inadequate tissue oxygenation Assessment Respiratory character and volume Depth of anesthesia Associated with pain Proper ET tube placement ET tube blockage Oxygen saturation Arterial or end-tidal CO2

Treatment of cyanosis/dyspnea 1. Check O2 flow meter 2. Turn off vaporizer and begin to bag the patient (IPPV) If the anesthetic machine is unavailable, an Ambu bag can be used to deliver room air 3. Reintubate if necessary 4. Continue until patient improves 5. Close monitoring to ensure that cardiac arrest does not occur Radiographs and thoracocentesis might be needed

TACHYPNEA TACHYPNEA: rapid respirations CAUSES: Surgical stimulation Commonly seen with opioid use Associated with light anesthesia accompanied by tachycardia and spontaneous movement May be seen in hyperthermic animals

TREATMENT OF TACHYPNEA CHECK ANESTHETIC DEPTH Is the animal too light? CAPNOGRAPH READING Obese patients Assist or control ventilation

RESPIRATORY ARREST Not all cases require immediate action by the anesthetist: Cessation of respiratory efforts Can lead to cardiac arrest Temporary arrest May follow injection of respiratory depressants or following a period of prolonged bagging Evaluate other vital signs HR/pulse quality: MM: ECG Pulse oximeter reading:

Respiratory arrest (Cont’d) True arrest Requires immediate action Can result from anesthetic overdose, cessation of oxygen flow, or preexisting respiratory disease May be preceded by dyspnea or cyanosis and abnormal vital signs May use Ambu bag, mouth-to-ET tube, or mouth-to-muzzle resuscitation

Use of an Ambu Bag

TREATMENT OF TRUE RESPIRATORY ARREST 1. NOTIFY THE VETERINARIAN 2. Turn off the vaporizer 3. Place ET tube if not already done Emergency tracheotomy? http://www.youtube.com/watch?v=3doQewrHdhQ 4.Monitor for cardiac arrest 5.Restore oxygen flow and begin bagging the patient 6. Continue bagging every 5 seconds until vital signs improve 7. Administer shock fluids 8. Preserve warmth

CARDIAC ARREST Cardiac arrest Some prior warning is usually present No heartbeat is auscultated or palpated Normal QRS complexes are absent No arterial pulse and blood pressure <25 mm Hg Gray or cyanotic mucous membranes Widely dilated pupils, no corneal reflex Agonal breathing Some prior warning is usually present Respiratory distress or arrest, cyanosis/dyspnea, prolonged capillary refill time, arrhythmia

CARDIAC ARREST - ABCDEF There is a critical 4 MIN window to restore oxygen delivery to the brain! Five people (ideal) involved 1 performs chest compressions 2 bags the animal 3 assesses the pulse during compressions and checks the pulse or ECG when compressions are stopped 4 draws up and administers drugs as per the veterinarian’s instructions 5 maintains a record of the patient’s status and resuscitative treatment

Anesthetic Problems and Emergencies Cardiac arrest with CPCR A = airway B = breathing C = circulation D = drugs E = ECG Circulation is the most important step so the correct order is CABDE

CARDIAC ARREST - ABCDEF AIRWAY and BREATHING; IMMEDIATELY CALL FOR HELP, NOTE THE TIME! An Endotracheal tube must be placed! Begin bagging at 1 breath every 10-12 seconds Do not overinflate

CARDIAC ARREST - ABCDEF CIRCULATION – cardiac compressions should be initiated POSITIONING: right side down with feet toward the compressor LARGE DOGS: The heel of the compressor’s hand should compress the chest against a firm object placed under the dog’s chest just behind the elbow. Also, dog can be placed in dorsal recumbency and compression applied to the caudal 1/3 of the sternum

CARDIAC ARREST - ABCDEF Medium sized dogs: The chest is compressed between two hands, one underneath the chest and the other at the 5th intercostal space over the heart itself. Small dogs or cats: compression applied using the thumb to compress the chest against the fingers of the same hand.

Circulation Most important factor is return of spontaneous circulation (ROSC) Cardiac compressions Method depends on the size of the animal Compress chest about 1/3 the diameter of the chest wall 1-2 compressions/second generates 100 bpm heart rate Compressions manually force blood through the heart and into tissues Each compression should produce a palpable femoral pulse

Circulation (Cont’d) Bag the patient every 10-12 seconds Simultaneously with compressions Some results should be seen within 2 minutes Internal compressions may be necessary Resuscitation is unlikely to be successful after 15 minutes Once spontaneous cardiac contractions are established, continue bagging until spontaneous breathing is established (several hours)

These patients are not on their right side- boooo

CARDIAC ARREST - ABCDEF Drugs Veterinarian authorizes dosage, route, and nature of drugs Catheterized animals Drugs administered IV followed by rapid fluid administration Be careful of overhydration Injections into the base of the tongue or by the intratracheal route are the second choice Intracardiac injections should be avoided

Commonly used drugs Epinephrine Vasopressin Atropine Cardiac arrest Vasopressin In place of or alternated with epinephrine Atropine Anesthesia-related cardiac arrest Dopamine or dobutamine Increase force and rate of cardiac contractions

Monitor cardiovascular and respiratory function Blood pressure, blood gases, pulse oximetry, ECG, capnography Drug and fluid therapy varies Assess brain function Repeat arrest within 24 hours is common Following successful ROSC, other conditions may arise Pulmonary or cerebral edema

CARDIAC ARREST - ABCDEF ECG Periodically check for spontaneous contractions by discontinuing external compression and either palpating for a pulse or looking for QRS complexes on the ECG. Differentiate between different forms of cardiac arrest to more effectively pick the treatment

ECG Don’t use alcohol if a defibrillator is present Asystole No electrical activity Ventricular fibrillation Coarse vertical zig-zag lines resulting from disorganized muscular heart activity Pulseless electrical activity (electromechanical dissociation, EMD) Normal or near-normal complexes

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 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

Seizures should be differentiated from excitement 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 excitement

Dyspnea in cats Dyspnea is usually 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) during inspiration Differentiate from growling during expiration May resolve itself or may need oxygen administration via facemask, intubation, or a tracheotomy Is easier to prevent than treat

Dyspnea in dogs Breed-related Airway obstruction 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