Pre anesthetic work up Flashcards

Question

5 classes of patients based on anaesthetic risk

Answer 1

PS1 minimal risk PS2 Low risk PS3 moderate risk PS4 high risk PS5 extreme risk; patient will die without procedure

Answer 2

Based on minimal patient database 5 classes of patients based on anaesthetic risk There is NEVER no risk

Answer 3

Goal: stabilise patient as much as possible prior to any anaesthetic/surgical procedure; this ensures least patient risk Depends on whether procedure is elective, required or emergency

Answer 4

Fluids to restore dehydration Postpone until ideal BCS Stop bleeding, treat infections, blood transfusions In the event of an emergency, you may not be able to wait and “E” is placed after PS score. Example: PS3E

Answer 5

CNS depression Suppression of hypothalamic control of temp and other homeostatic functions Also decreases ability to vasoconstrict in response to any drops in blood pressure Decreased HR, cardiac output Decreased RR, tidal volume Vasodilation due to gas anaesthetics will contribute to hypotension Risk of esophageal reflux and aspiration pneumonia

Answer 6

Fasting Temp support O2 support Fluid support Patient monitoring

Answer 7

Fast = no food, can have water NPO= nil per os= nothing per mouth= no food or water Fasting is important before anesthetic induction Decreases risk associated with vomit and regurgitation during induction, surgery and recovery Job of RVT to instruct client on fasting protocol BEFORE surgery date Must confirm at time of admitting that patient was fated If the client is uncertain, assume the patient has not been fasted. May require postponing surgery

Answer 8

Food: 8-12h Water: 2-4h

Answer 9

Food: 8-12h Water: 0-2h Horses have risk of gastric ulceration if empty stomach; OK if horse gets small mount of hay if anaesthetic is short

Answer 10

Food: 24-48h water; 8-12h

Answer 11

Food: 12-18h Water: 8-12h

Answer 12

Patients less then 2 kg Neonates <8 weeks Exotics Diabetics- also need to instruct on insulin Patients with cachexia or less than ideal BCS There is an increased risk of hypoglycemia in all of the above groups

Answer 13

Emergent cases may not have time to fast Need to weigh risk of postponing surgery against possible complications Options Increase monitoring Use positioning of body to decrease risk of aspiration Can induce vomit Can place stomach tube

Answer 14

Esophageal reflux Esophageal trauma Aspiration pneumonia

Answer 15

Different from vomiting Gastroesophageal sphincter relaxes under GA→ when patient is in lateral, there is passive flow of stomach contents into the esophagus Risk of reflux increases if not fasted Occurs intraop and recovery (risk until patient can swallow and hold head)

Answer 16

Complication of esophageal reflux Stomach acid enters esophagus and causes damage to the esophageal lining Clinical signs: vomit, nausea, dysphagia, post op anorexia If severe enough, this could eventually lead to esophageal stricture- scar tissue develops where trauma occurred

Answer 17

Complications of esophageal reflux Stomach contents flow into oral cavity and from the oral cavity, enter the airways while patient is recumbent high risk during recovery

Answer 18

Filling of alveoli with fluid (acute airway obstruction) Infection and inflammation of the lungs (24-72 h post op) Can be very severe, fatal

Answer 19

Crackles on auscultation Decreased oxygenation; cyanosis Fluid oral cavity Fluid from nares Post op ADR, fever, increased resp sounds, tachypnea

Answer 20

Fasting Keep ETT cuff inflated until patient swallows Stomach tube Patient positioning If patient has not aspirated yet but is at risk Lateral? If patient has aspirated and is unconscious Sternal?

Answer 21

Nausea V/D Side effect of hydro and/or GA Filled intestines and bladder Decreases accessibility to abdominal organs Increased risk of contamination Longer surgery times Bloating in ruminants Require a stomach tube to release rumen gasses even if they have been fasted

Answer 22

Thermoregulation is a homeostatic process controlled by the hypothalamus Core heating is by - Shivering, muscle contraction, increased metabolic rate, vasoconstriction of peripheral blood vessels Core cooling is by - Decreased metabolic rate, vasodilation of peripheral blood vessels, panting, salivation, sweating

Answer 23

Depression of the hypothalamus (thermoregulatory centre) Decreased metabolic rate Muscles don't contract/loss of shiver Vasodilation (especially acepromazine and inhalants) Cold 100% O2 Open body cavity (especially if open abdomen) Evaporation of alcohol during surgical prep Conduction loss to stainless steel

Answer 24

Intrinsic (patient) factors that cant be altered - BCS - Size of animal – smaller animals have higher surface area to body mass so lose heat faster - Neonates and geriatrics have less thermoregulation Extrinsic (external) factors that can be altered - Drug selection – some cause more vasodilation than others - Ambient temp - Duration of GA – longer procedure = colder - Degree of shaving and type/volume of surgical scrub

Answer 25

Know temp BEFORE premedicating From the time of induction, monitor every 15 minutes until patient is recovered After recovery, monitor every 30 min until patient can sustain temperature >37.4 °C Methods: Esophageal thermometer - most accurate Rectal thermometer – most convenient Axillary/ear is not accurate enough

Answer 26

36-38 °C – allowable range under GA >37.4 °C – patient can maintain own temp; do not heat 36-37 °C – must provide active heating support <36 °C – must inform DVM <33 °C – dying

Answer 27

Prolongs anaesthetic recovery and general recovery (especially in cats) Predisposes patient to anaesthetic overdose Due to decreased metabolism of drugs Can maintain cool patients on lower anaesthetic dose Shivering during recovery will increase oxygen demands Below 33*C, brainstem is depressed and theres is cardiac malfunction

Answer 28

Stabilize room temperature prior to premedication (turn up heat, especially in winter) Prudent use of alcohol and scrub water (don’t drown your patient; remove excess scrub/alcohol) Place barrier between patient and table top Warm IV fluids to ~37.5°C; same for saline used for abdominal flushes Blankets, circulating warm water blanket; forced warm air blanket (Bair huggers); warm water bottles Minimize surgical and general anesthetic times

Answer 29

Electric Heating pads and Lamps - Often poor control and get too hot - Sedated/anesthetized patient can’t move away - Cause contact area burns (even if mild heat for a prolonged time) - Especially cats (genetic predisposition) - ~ 1 week to appear; can cause sepsis Aggressive heating of exterior body surface - Causes peripheral vasodilation (body thinks it is too hot vasodilation of surface capillaries cooled blood from surface goes to core and drops temp furthe

Answer 30

>39 °C Most often seen just before/during recovery Causes from most to least common: Excessive external heat source (too much warming) Cat that reacts to mu-agonists (hydromorphone, fentanyl) Malignant hyperthermia (rare, more common in pigs)

Answer 31

Remove heat source; fans Reverse drug if possible Cold IV fluids Turn up 100% oxygen flow

Answer 32

Decreased RR and tidal volume with Mu-agonsits Alpha-2 agonists (all species; most severe in ruminants) ALL general anesthetics Propofol, alfaxalone cause induction apnea Isoflurane suppresses CO2 drive Decreased ventilation results in less O2 uptake and decreased CO2 exhaustion Also decreases ability to move O2 and CO2 around body

Answer 33

Patients under GA require a minimum of 33% O2 to maintain oxygen saturation of blood Room air is 21% O2; not sufficient to meet tissue demands when combined with depresses resp function Must have 100% O2 support to achieve maximum oxygen saturation of blood

Answer 34

Tidal volume already decreased under GA Increased weight requires more effort to expand and expel lungs: especially if animal is recumbent Dependant lung areas (“down” side of patient in lateral) may develop atelectasis Alveoli partially collapse in this area due to poor inflation Applies to Morbidity obese animals Large animals (Eq, Bovine) May require manual/automatic ventilation

Answer 35

Risk of soft palate collapse. If animal also has stenotic nares, their entire airway could be cut-off Watch for resp distress, increasing lethargy, cyanosis Continuous monitoring from time of sedation until completely recovered Worst risk is sedation and recovery (i.e., not intubated) When intubated, will breathe better then they ever have before. May keep ETT in even after recovered (do not pull with swallow); release cuff so animal can pull out on own when they want Be aware patient may also have collapsing trachea and size ETT appropriately

Answer 36

Normal BP (no medications): 120/80 (94) Varies with age, species, health status, and situation

Answer 37

HR Cardiac output Degree of vascular contraction Oncotic pressure (presence of albumin and colloids in plasma keep water in the blood vessels) Fluid volume Adequate BP required for delivery of O2 and nutrients to cells; removal of CO2 and waste products

Answer 38

There is always a drop in BP under GA Degree of hypotension depends on Drugs used (inhalants, acepromazine, alpha-2) Patient stability (underlying cardiovascular/renal disease; hydration status; geriatrics and neonates) Duration of GA Any blood loss will contribute to hypotension

Answer 39

Decreased cardiac function - Decreased HR, decreased cardiac output - Less volume of blood moved per unit time - Most severe depression by alpha-2 agonists, inhalants, injectable anesthetics - If severe enough, can cause cardiogenic shock Vasodilation - Inhalant anesthetics, acepromazine - Causes a relative decrease in fluid volume; with time, fluid moves from interstitial space to vascular space - If severe enough, could result in vasogenic shock Evaporative losses - Open body cavities, dry gasses - Real loss of fluid volume Perioperative hemorrhage - Can be minimal to severe - Real loss of fluid volume

Answer 40

It is best to IV catheterize patients under heavy sedation and/or GA Benefits Can deliver IV fluids to maintain blood volume & support blood pressure Can be hard to get IV access later due to low BP Rapid administration for emergency drugs Used to administer CRI’s Reduces the risk of perivascular injection Can administer a number of IV drugs one after another with flushing between each one (trauma)

Answer 41

Dog, cat: 110-160/50-70 (60-90) Eq: >80/>50 (60-90)

Answer 42

Dog, cat Systolic <90; MAP <70; Diastolic <40 Eq Systolic <90; MAP <80; Diastolic <40

Answer 43

Amount of fluids required to maintain BP in the presence of drugs that cause cardiac depression and vasodilation ALWAYS recommended Isotonic cystalloids (LRS, Normosol, Plasmalyte) appropriate for most patients Administer via IV catheter

Answer 44

From time of induction until patient is recovered Any dehydration is corrected BEFORE general anesthesia (not part of surgical rate) Return to appropriate maintenance rate after recovery to prevent fluid overload Must record fluid type, rate, total volume(or start and stop times), any changes in fluid rate as they occur

Answer 45

Surgical fluid rate in otherwise healthy patient: CATS: 2-3 ml/kg/h DOGS: 3-5 ml/kg/h Large animal: 5-10ml/kg/h This rate is used on its own! Adjust with changes in BP, lungs sounds, HR, bleeding.... Know THIS rate for exam purposes!

Answer 46

Given when patients are hypotensive (despite surgical fluid rate) or bleeding profusely I.e., when the surgical fluid rate is not enough Start with a SINGLE crystalloid bolus 10 ml/kg over 15 min Can repeat up to 3-4 times if necessary Check with the vet before administering

Answer 47

Offsets causes of hypotension (vasodilation and decreased cardiac output) Treats fluid loss Supports tissues that receive the most blood flow Kidneys > brain > heart Even mild hypotension can result in post-anesthetic renal damage Also corrects electrolyte and acid-base imbalances (commonly occur under GA and with pathology) Supports renal drug elimination

Answer 48

Too much fluid (excessive total volume infused) Too fast fluids - Giving fluids too fast prevents them from entering into the extracellular fluid volume properly Given the appropriate rate and volume to the wrong patient Hct <20 Low albumin Patients < 5 kg Heart failure Renal disease

Answer 49

Hypertension Very bad if pre-existing heart disease; causes heart to work harder and can cause cardiac overload Increases blood loss Fluids move to 3rd spaces in the body (abdomen, pleural space, pulmonary spaces) Pulmonary edema Cerebral edema Can dilute oxygen carrying capacity of blood

Answer 50

Increased Lung sounds/Crackles ↑respiratory rate and dyspnea Coughing and restlessness if patient is awake Tachycardia Increased BP Hemodilution (decrease the relative PCV) Ocular and nasal discharge, chemosis Subcutaneous edema Neurological signs

Answer 51

Know your calculations Use an appropriate-sized fluid bag (ex. 100 ml for cat spay) Clamp off the line when transporting patients Check IV line and rate hourly. Caution: most drip sets will alter their rate slowly over time. Ideally, use an infusion pump Monitor equipment Monitor patient

Answer 52

No definitive therapy Main treatments: Discontinue fluids Start on diuretics Provide oxygen support Best to prevent fluid overload rather than treat it!

Answer 53

Convert weight to kilograms Calculate the hourly rate ml/h (SA); L/h (LA) Always enter this value into the medical notes Then, calculate the drip rate from the above Whole drops per whole seconds Drip sets : >10-15 kg: 10 drop/ml set <10 kg: 60 drop/ml set (aka “pediatric” set) Double check your numbers and make sure that they MAKE SENSE. For example, you would never give 50 ml/h to a cat Mark your fluid bag with “Start” and “End” so you know how much fluid your patient has received = total volume infused. Be aware that certain patients will have altered rates. Heart failure and renal disease may require decreased fluid rates; fever and younger animals require high rates, etc. If in doubt, ask.

Pre anesthetic work up Flashcards

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