Advanced Anesthesia Monitoring

Inadequate training

Personnel who are not properly trained running anesthesia, cannot register abnormalities or how to address them

Lack of familiarity

Anesthesia is constantly changing → new technology and anesthetic agents are introduced, high level of comfort must require full dedication and time to learn it, training sessions are important

Failure to adequately prepare patient

Failing to ask important questions that could hinder anesthetic protocols

Drug calculation or administration errors

Many agents have a narrow margin or safety, failure to weigh the patient appropriately, math errors, wrong medication used, incorrect route administered, confusion between syringes

Errors caused by fatigue, hate, or inattention

Rushed or tired nurses/personnel are more likely to make mistakes, ask for help or take a break if needed!, inattention to parameters can lead to emergencies

Equipment related issues

Machines, monitors and associated equipment all require regular maintenance, failure to use equipment correctly can cause anesthetic complications, inappropriately setting up the machine can be fatal

High risk patients

Neonates, geriatrics, brachycephalic, sighthounds (long muzzle dogs), obese animals, trauma related emergencies, cardiac, renal, and hepatic related diseases

What do neonates have an increased risk of?

Hypothermia, dehydration, overhydration, hypoxemia, hypotension, hypoventilation, hypoglycemia

Neonate monitoring

is similar to adult anesthesia but have different normal values- higher heart rate + respiratory rates, slightly lower blood pressure than adults, watch closely for bradycardia in neonates

Strategies used to decrease neonate risk

Minimize heat loss, avoid prolonged fasting and don’t withhold water, consider IV 5% dextrose in isotonic crystalloids using infusion pump, weigh the patient accurately and dilute injectable drugs if necessary, reduce anesthetic doses, inhalant agent preferred to injectables, minimize dead space

Factors that increase risk for geriatrics

Reduced organ function, poor response to stress, serious illness not uncommon, increased susceptibility to hypothermia, hypotension, respiratory depression and overhydration

Strategies to use for geriatric patients

carefully assess and stabilize the patient prior to procedure, use premeds to minimize adverse effects of general anesthetics, reduce anesthetic doses by 30-50%, allow longer time for response to drugs, administer fluids at reduced rate, keep patient warm

Oxygen for geriatric patients

Pre-oxygenate for at least 3 minutes prior to surgery and during post op recovery after extubation

Geriatric patient history

Pay special attention for diabetes, hyperadrenocorticoism, hypothyroidism

Geriatric recovery

Keep a close eye, stay warm, monitor for aspiration pneumonia (keep sternal)

Factors that increase risk for obese patients

accurate dosing difficult, may have respiratory difficulties, may exhibit rapid, shallow respirations

Strategies for obese patients

determine dose according to ideal weight, preoxygenate, induce rapidly, assist ventilation if necessary, delay extubation, observe closely in recovery

Obese patients and anesthetics

Obese patients have higher percentage of body fat than patients of normal body weight, since blood supply to fat is low → anesthetics is not efficiently distributed to fat store

Obese patients and respiration

Usually have some degree of respiratory difficulty, pre-oxygenate for 5 minutes prior to induction, often exhibt rapid, shallow respirations during anesthesia → result in hypercapnia or/and difficulty keeping patient under anesthesia

Factors that increase risk for brachycephalic patients

Conformational tendency toward airway obstruction, abnormally high parasympathetic tone, small trachea in comparison with physical body size

Strategies for brachycephalic patients

Include anticholinergic in anesthestic protocol, preoxygenate, rapid induction using IV agents, place ET quickly and efficiently; may need a smaller diameter tube

Factors that increase risk for sighthound patients

Increased sensitive to barbiturates

Strategies for sighthound patients

Use alternative agent

Brachycephalic characteristics that impede air exchange

stenoic nares, elongated soft palate, everted laryngeal saccules, small diameter trachea

Brachycephalic recovery

Leave ETT in as long as possible..until walking out the door!, have propofol, tube, and oxygen ready in case of reintubation if emergency happens post extubation, keep excitement and stress to a minimum to prevent hyperventilation/respiratory distress, steroids can be helpful in minimizing airway swelling

Sighthound anesthesia

Greyhounds, Saluki, Afghan hound, Whippet and Russian Wolfhound show increased sensitivity to some anesthetic agents, used to be sensitive to thiobarbiturates, now we used propfol, midazolam, diazepam + ketamine, alfaxalone to avoid this sensitivity

Factors that increase risk for cardiovascular disease patients

Circulation is compromised, pulmonary edema common, increased tendency to develop arrhythmias, tachycardia and overhydration

Strategies for cardiovascular disease patients

Identify specific disease process through careful patient assessment and stabilize as needed, minimize stress and restrain gently, customize anesthetic protocol for each patient, monitor carefully for changes in cardiopulmonary function, preoxygenate for 5 min before induction, avoid agents that depress myocardial contractility, increase cardiac work, or cause arrhythmias, avoid overhydration, titrate drug dosages

Anesthesia for cardiovascular disease patients

Careful PE w/ special focus on cardiovascular system, keep stress to a minimum, manage dehydration and hypovolemia, pre-oxygenate for 5 min prior to induction, reduced fluid rate (1-3 ml/kg/hr)

Factors that increase risk for respiratory disease patients

Poor oxygenation of tissues, patient may be anxious and difficult to restrain

Strategies for respiratory disease patients

Stabilize prior to induction, preoxygenate but avoid stress and unnecessary handling, induce with injectable agents, intubate rapidly and control ventilation if necessary, be prepared to perform tracheostomy, check airway frequently and avoid compressing chest, monitor SpO2 and end-tidal CO2, monitor closely during recovery

Respiratory disease patient anesthesia

Thorough PE and blood work and x-rays, minimize stress, avoid dorsal or lateral recumbency, avoid drugs that cause respiratory depression or cause upper airway muscle relaxation (collapse airway)

Respiratory disease patient recovery

swab/suction mouth and throat out after extubation to prevent obstruction, may require oxygen therapy post extubation

Factors that increase risk for hepatic disease patients

Delayed metabolism of anesthetic agents, decreased synthesis of blood clotting factors, may be hypoproteinemic, dehydration common; may be anemic and/or icteric

Strategies for hepatic disease patients

Base protocol on results of preanesthetic blood work and other tests, may reduce dosages of, or omit preanesthetic medication, inhalation agents preferred over injectable agents, expect prolonged recovery, reversible agents are preferred

Hepatic disease patient anesthesia

Acepromazine + benzodiazpines should be avoided in hepatic disease patients, short acting drugs that require minimal hepatic metabolism should be used - isoflurane or sevoflurane

Characteristics of hepatic disease patients

Dehydrated, thin, icteric, anemia, may also have hepatic encephalopathy, have low BG and should be check prior to anesthesia

Factors that increase risk for renal disease patients

Electrolyte imbalances common, including hyperkalemia and metabolic acidosis, dehydration usually present, delayed excretion of anesthetic agents

Strategies for renal disease patients

Withhold water for 1h or less, rehydrate before surgery, obtain renal function test results and electrolyte values, and address abnormalities, administer intraoperative IV fluids at appropriate rates, reduce doses of anesthetic agents, monitor blood pressure and manage hypotension promptly

Renal disease patient anesthesia

Prior bloodwork (BUN, creatinine, SDMA), pre-op water deprivation isn’t recommended, maintain adequate renal perfusion during anesthesia, anesthesia may be hazardous because renal blood flow is decreased during anesthesia and renal function may be further compromised (injectable NSAIDS may reduce renal perfusion)

Factors that increase risk for c-section dam

Increased workload to heart, respiration may be compromised, increased risk of vomiting or regurgitation, increased risk of hypotension and hemorrhage

Factors that increase risk for c-section offspring

Anesthetic agents cross placenta and may reduce respiratory and cardiovascular function, hypoxemia and hypercapnia secondary to respiratory depression

Strategies for c-section dam

Administer IV fluids, clip, prep and establish IV access before induction, pre-oxygenate, use lowest effective dose of general anesthetic, induce IV and intubate quickly, consider epidural analgesia combined with neuroleptanalgesia, monitor for vomiting during recovery

Strategies for c-section offspring

Clear airway with bulb syringe, use reversal agents under the tongue to stimulate breathing, administer oxygen by face mask, administer atropine for bradycardia

Factors that increase risk for trauma patients

Respiratory distress common, cardiac arrhythmias common for 72h after incident, shock and hemorrhage common, internal injuries often present

Strategies for trauma patients

Thorough physical examination necessary to check for concurrent injuries, obtain thoracic radiographs and electrocardiogram, stabilize before anesthesia, preoxygenate

Trauma patient problems

May have problems affecting multiple body systems that greatly increase anesthetic risk, any of these can lead to decrease in oxygen exchange which will lead to cardiovascular issues, loss of blood results in hypotension and anemia may be present, stabilize patients prior to anesthesia

Emergency anesthetic situations

Animals that will not stay anesthetized, animals that are too deeply anesthetized, pale MM, prolonged CRT, hypotension, dyspnea and/or cyanosis, tachypnea, abnormalities in cardiac rate and rhythm, apnea, respiratory arrest, cardiac arrest

Reasons patients might not stay anesthetized

Inadequate vaporizer setting, vaporizer that is inadequately filled with liquid anesthetic, blocked, misplaced or disconnected ETT, ETT is too small or inadequately cuffed, apnea or inadequate tidal volume (occurs after induction with IV agent), misassembly or leakage of anesthetic machine, inadequate oxygen flow, malfunction or incorrect calibration of vaporizer

Signs a patient is too deep

RR of 6 breaths/min or fewer, shallow respirations or exaggerated respiratory movements, pale or cyanotic MM, CRT >2secs, bradycardia, weak pulse, hypotension, cardiac arrhythmias, cold extremities, absent reflexes, including palpebral + corneal reflexes, flaccid muscle tone, dilated pupils

What to do with patients that are too deep

Decrease vaporizer setting and inform DVM, if DVM has warranted resuscitation efforts are warranted begin to ventilate pure oxygen (every 5 seconds until signs of recovery), use of IV fluids, external heat and drugs such as specific reversing agents may also expedite recovery, when in doubt turn it down while carefully observing patient for signs of arousal (If DVM is unable to check)

Treating pale MM

ascertain the animal’s anesthetic depth and monitor vital signs; rule out → hypothermia, hypotension, drug reactions, blood loss, pain; consult with DVM to possibly administer pain medications or other drugs or to initiate treatments (warming patient, IV fluid therapy, blood transfusion)

Causes of pale MM

Anemia, blood loss, hypotension, hypothermia, pain, peripheral vasoconstriction

Treating prolonged CRT

Immediately check the animal’s pulse and blood pressure reading, closely observe patient for other signs of shock → hypothermia and tachycardia

Treatment of hypotension

Reduce anesthetic depth, use of anesthetic drugs that cause vasodilation should be minimized, pain control should be optimized with injectable analgesics to allow inhalants to be decreased

Crystalloid fluids should be administered rapidly at 3-10ml/kg in dogs and 3-5ml/kg in cats

Bolus of 20-40ml/kg can be given over 15min for dogs and 10-20ml/kg for cats