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!

Can you spot the problem?

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

Propofol? IV IM or Sub Q

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  CO 2 ABSORBER EXHAUSTION *In re-breathing systems, if CO 2 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. ↑ CO 2 = Tachypnea, tachycardia, brick red mucous membranes, cardiac arrhythmias, respiratory acidosis Human error!

EQUIPMENT FAILURE  INSUFFICIENT O 2 FLOW You will need to check both the flowmeter and the oxygen tank pressure gauge. Oxygen tank runs out or leak Hose becomes disconnected Obstruction or leak occurs Knob can become stripped, check bobbin tract *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

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  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  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  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: Pleural effusionDiaphragmatic hernia PneumothoraxPneumonia Tracheal collapsePulmonary edema Clinical signs  Tachypnea  Dyspnea  Cyanosis

 Anesthetic considerations V T is reduced and respiratory rate is decreased in most anesthetized animals A decrease in V T 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

Respiratory Volumes  Tidal volume-  Inspiratory Reserve Volume  Expiratory Reserve Volume  Residual volume  Minute Volume

Respiratory Capacities (involve 2 or more pulmonary volumes)  Inspiratory Capacity  Functional Residual Capacity  Vital Capacity  Total Lung Capacity

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 Preanesthetic agents must be chosen with care

PATIENT FACTORS  RENAL DISEASE POTENTIAL PROBLEMS  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

How to fix it…  Low heart rate- access depth- BP, jaw tone, opiods. Fix- decrease anesthetic, consider anticholincergic Increased heart rate- same checks as above Fix – turn up gas But…. Low BP- HR increases as compensatory stage – decrease gas

Lost ECG or sudden abnormal reading  Check patients vitals manually  Check lead attachment, apply more alcohol  IF you cannot hear heart rate, tell DR.!

Low EtCO2  Check pulse and BP- precursor to cardiac arrest  If normal BP and pulse: check O2 flow rate  If BP is low- decrease anesthetic  High EtCO2- check trache tube, soda lime Then use ventilator, esp. in obese patients

Low Blood Pressure  Low- check cuff size, and position- is it on a joint?  Check with a doppler if oscillometic is being used  Check anesthetic depth, decrease vaporizer - Still low? - Try shock rate - Still low? - Alert vet and start colloids or what ever Dr. prescribes.

High Blood Pressure  Check cuff size and position  Check against doppler  Check anesthetic depth, and increase gas  Consider drugs given, type of surgery, or what surgeon is doing to patient at that time  Cut fluids off

I smell gas  Machine leak- sealed hoses  Trache tube leak  Inadequate machine scavenging system  Exhausted F-air canister  Loose vaporizer cap  Vaporizer leak