5a. Preanesthetic Work-Up

Question 1

What is the RVT checklist and what are some things that might be on it?

Answer 1

communication of procedures and risk w/ client
consent - written
min. patient database including dx
assess patient anesthetic risk
proper patient fasting
anesthetic and monitoring equipment working
surgical supplies and equipment are ready
Pre-induction patient care - sedation, pre-emptive analgesia, other meds, fluids, temp support, enemas, bandage removal and wound care

Question 2

What are some communicative do’s?

Answer 2

take time to commune w/ client
know pet/procedure being done
know patient hx and discuss possible complications
get accurate contact info
be honest about cost (include post-op follow up)
keep client informed, esp. if something goes wrong
know what clients wants in event of complications
be thorough about post surgical care reqs (especially post-op home care requirement

Question 3

What are some communicative dont’s?

Answer 3

NEVER guarantee a cure
Don’t assume that the client understands what is happening, or what is going on - must be able to explain procedures including sedation, anes., sx procedure, home care
Don’t lie to them about s/e and complications, about the cost and cost of complications and that complications/mistakes DO occur

Question 4

What is the minimum patient database?

Answer 4

1. patient signalment
2. Patient hx (current/chronic conditions, meds, prior anesthetics/surgeries)
3. weight, TPR, mentation
4. Complete PE
5. Pre-surg pain assessment
6. Pre-anes diagnostic workup

Question 5

What do we grab when we admit a patient and history?

Answer 5

admitting: confirm procedure, cost, contact info, CONSENT, confirm “what if” in case of complication, establish discharge (same day or hospital stay)
Hx: in clinic medical (incl. past labs) and anes hx, patient hx (chronic and acute), current meds, fasting?, water withdrawal?

Question 6

Why is signalment important?

Answer 6

horses and cats become excited on opioids
dosing requirements diff for every species
horses req dedicated recovery areas to prevent injury
large animals require ventilation support
exotics are handled differently

Question 7

Why do we care about the breed we’re operating on?

Answer 7

Breed specific MDR1-deficiency (border collies)
sighthounds sensitive to barbiturates
boxers sensitive to acepromazine; terries resistant to it
brachycephalic breed are difficult to intubate; require monitoring during sedation and recovery

Question 8

Why do we care about the age of the patient we are operating on?

Answer 8

geriatrics often have dec liver and renal functions and overall lowered anesthetic tolerance\neonates and pediatrics have higher fluid reqs, inc risk of hypothermia and diff drug metabolism

Question 9

Why is sex and repro status important in the patient we’re working on

Answer 9

preg patients always at risk for drug effects to both patient/fetus - inc CV demand, risk of abortion or teratogenicity
Select drugs that do not cross the placenta if possible
avoid acepromazine in stallions
benzodiazepines cause floppy baby syndrome
xylazine can cause abortion in cows/ewes

Question 10

Why do we perform a PE for premed?

Answer 10

PE and drug order for premed MUST be by the vet
Vet can perform the PE and give order up to 24h before procedure; in event; RVT MUST perform exam immediately (ensure no change in patient) before giving meds
minimal exam immediately before premed (weight, BCS, TPR, MM< hydration status, mentation status, MUST record all values and findings)

Question 11

What are some PE changes that could occur in 24 hours

Answer 11

hydration - skin tent, sunken eyes
Weight

Question 12

What normals do we need to memorize?

Answer 12

Temp, HR, RR, CRT, indicators of mild, mod and severe dehydration
record normal for patient
allowances while under anes alter depending on specific patients’ norms

Question 13

Why is weight/BCS important to know before surgery?

Answer 13

in-clinic patients should be weighed minimum of 124h
ALL anes. patients be weighed on day of
Most important short term weight change is hydration
Must know BCS for ideal BW
if low BCS, need to considered hypoalbuminemia, low body fat, illness
If High BCS, will need to consider lean BW for dosing, underlying cardiac dz, inc resp dep, under GA, fatty liver syndrome in cat post-op

Question 14

Why is mentation important for surgery?

Answer 14

Gives indication of underlying illness, CNS status. patients w/ dec mentation have inc risk under GA
Part of distance exam,
lvls: BAR, QAR, lethargic, obtunded, suporous (aroused by painful stimuli), comatose

Question 15

What are things we MUST report to DVM when doing a PE before giving premeds?

Answer 15

change in weight, hypo/hyperthermia, abnormal HR< rhythm, or murmur; weak, overly strong (bounding) or irregular pulse
inc resp rate or effort: altered lung sounds
delayed CRT; pale, cyanotic or icteric MM
dehydration
cachexia
change in mentation or neurological changes
vomit

Question 16

What are some additional diagnostics that can be done pre-surgery?

Answer 16

min tests: PCV, TP< BUN, BG
can be done immediately prior to anes or within a reasonable time frame (young patient who is healthy, old patient who is otherwise healthy, patient hit by car 3 d ago)
when testing is declined in whole or part there should be signed consent form

Question 17

What do we need to record on our anes exam findings?

Answer 17

drug patient is taking
current weight and BCS
TPR, MM, CRT, mentation
anything abnormal
anything examined and found abnormal
also, verbally communicate any abnormalities to VIC

Question 18

What is the physical status classification

Answer 18

based on minimal patient database
PS1 minimal risk
PS2 low risk
PS3 moderate risk
PS4 high risk
PS5 extreme risk, patient will die w/o procedure
There is NEVER no risk

Question 19

What is the risk level of PS1? Give the criteria and an example of it

Answer 19

minimal - normal, healthy and not old/very young. Ideal BCS
Young to middle age patients
electives (Spay, neuter)
dental trophy (gr1-2 dental disease)

Question 20

What is the risk level of PS2, what is the criteria and examples?

Answer 20

low - may have mild systemic dz or slight altered drug metabolism
Neonates, pediatric, geriatric, brachycephalic, mild collapsing
trachea
- Mild chronic liver, renal change, low grade murmur, controlled
hypertension, diabetes
- Mild obesity
- Pregnancy
- Mild dehydration (<3%)

Question 21

What is the risk level of PS3, the criteria and an example of it

Answer 21

moderate - has severe systemic disease that is well managed
- Moderate dehydration (3-5%)
- Anemia
- Compensated major organ disease (chronic renal disease, controlled
heart failure)
- Moderate-severe collapsing trachea w/ dyspneic episodes
- Addison’s
- FB gastrotomy, cystotomy

Question 22

What is the risk level of PS4, the criteria and an example of it?

Answer 22

High - has severe systemic disease that is a (constant) threat to life
- Stage 3 heart failure; stage 3 renal disease, liver failure
- Ruptured bladder, pyometra, internal hemorrhage, pneumothorax

Question 23

What is the risk level of PS5, criteria and an example of it

Answer 23

extreme, survival not likely - MORIBUND. not expected to survive beyond 24h w/o the procedure. Chances of surviving procedure very low
Bleeding out and cannot control blood loss
- Hypothermia
- GVD
- Perforated linear FB with peritonitis
- Stage 4 heart failure, stage 4 kidney failure; end stage liver failure
- Imminent death: multi-organ failure

Question 24

What is the goal of pre-op stabilizing?

Answer 24

stabalize patient as much as possible prior to any anesthetic/surgical procedure; ensures least patient risk
Depends on whether procedure is elective, required on emergency
Stabilization: fluids to restore dehydration, postpone until ideal BCS, stop bleeding, treat infections, blood transfusions
In event of emergency, many not be able to wait “E” is placed after PS score ex: PS3e

Question 25

Why are healthy geriatrics considered PS2?

Answer 25

We can see a lot of decline in kidney and liver function before it shows on any diagnostic tests

Question 26

What are the inherent risks of GA

Answer 26

1. CNS depression - suppression of hypothalamic control of temp and other homeostatic func and also dec ability to vasoconstrict in response to any drops in BP 2. Dec HR, cardiac output 3. Dec RR, tidal volume 4. Vasodilation due to gas anesthetics will contribute to hypotension 5. Risk of esophageal reflux and aspiration pneumonia

Question 27

How can we limit the inherent risks of GA?

Answer 27

fasting, temp support, O support, fluids and patient monitoring

Question 28

What is fasting?

Answer 28

FAST = no food; can have water NPO = nil per os = no food/water Fasting is important before anes induction dec risk associated w/ vomit and regurg during induction, sx and recovery Job of RVT to instruct client on fasting protocol before surgery date MUST confirm at time of admitting that patient was fasted - if uncertain, assume patient has not been fasted. may require postponing surgery

Question 29

What is the standards hours to withold food and water in cats and dogs?

Answer 29

Food: 8-12hrs Water: 2-4

Question 30

What are the standard hours to withhold food and water in horses?

Answer 30

Food: 8-12 Water: 0-2

Question 31

What are the standard hours to withhold food and water in cattle

Answer 31

Food:24-48 hours Water: 8-12 hours

Question 32

What are the standard hours to withhold food and water in small ruminants?

Answer 32

Food: 12-18 hours Water: 8-12 hours

Question 33

What are the standard hours to withhold food and water in patients <2kg/exotics?

Answer 33

Food: should be fasted for shorter tims or not at all Water: for shorter times

Question 34

What is one reason that we might be able to still give a small amount of hay to horses that may need to be fasted?

Answer 34

Horses has risk of gastric ulceration if empty stomach

Question 35

What special patient groups require special fasting requirements

Answer 35

Patients less than 2kg Neonates <8wks Exotics Diabetics - also need to instruct on insulin Patients w/ cachexia or less than ideal BCS There is an increased risk of hypoglycemia in ALL of above groups

Question 36

In what times might fasting simply not be an option? What can do we instead?

Answer 36

Emergencies - 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

Question 37

What are the complications of not fasting?

Answer 37

esophageal reflux, esophageal trauma/esophagitis, aspiration pneumonia, Other common ones: nausea, V/D (s/e of hydro and/or GA), filled intestines and bladder (dec accessibility to abdominal organs, inc risk of contam, longer sx times), bloating in ruminants -require a stomach tube to release rumen gasses even if they have been fasted

Question 38

What is esophageal reflux

Answer 38

different from vomiting gastroesophageal sphincter releaxes under GA > when patient is in lateral, there is passive flow of stomach contents into the esophagus risk of reflus inc if not fasted occurs intra-op AND recovery (risk until patient can swallow AND hold up head

Question 39

what is esophageal trauma

Answer 39

esophagitis complication of esophageal reflux stomach acid enters esophagus and causes damage to the esophageal lining clinical signs: vomit, nausea, dysphagia, post-operative anorexia if severe enough, this could eventually lead to esophageal stricture - scar tissue develops where trauma occurred

Question 40

What is aspiration pneumonia

Answer 40

complication of esophageal reflux stomach contents flow into oral cavity and from the oral cavity, enter the airways while patient is recumbent Causes: filling of alveoli with fluid (acute airway obstruction), infection and inflam of the lungs (24-72 h post-op), can be very severe, fatal Highest risk is recovery - in sx, airway is protected by cuff, but after it is not

Question 41

How do we diagnose aspiration pneumonia?

Answer 41

crackles on auscultation decreased oxygenation; cyanosis fluid from oral cavity fluid from nares post-op ADR, fever, increased resp sounds, tachypnea

Question 42

How do we prevent aspiration pneumonia

Answer 42

fasting, keep ETT cuff inflated until patient swallows stomach tube patient positioning If patient has NOT aspirated yet but is at risk - position head up body down to prevent aspiration If patient has aspirated and is unconscious - head down so gravity drains fluid

Question 43

What is thermoregulation? What is core heating and cooling caused by?

Answer 43

homeostatic process controlled by the hypothalamus core heating: shivering, muscle contraction, inc metabolic rate, vasoconstriction of peripheral blood vessels Cooling: dec metab rate, vasodilation of peripheral blood, panting, salivation, sweating

Question 44

What are the major causes of temperature drop during GA?

Answer 44

1. depression of hypothalamus (thermoregulatory centre) 2. decreased metabolic rate 3. Muscles don't cntract/loss of shiver 4. vasodilation (especially acepromazine and inhalants) 5. Cold 100% oxygen 6. Open body cavity (especially if open abdomen) 7. Evaporation of alcohol during surgical prep 8. Conduction loss to stainless steel

Question 45

What are some factors that might affect heat loss

Answer 45

intrinsic (patient) factors that can't be altered - BCS, size of animal (smler have higher surface area to body mass so lose heat faster, neonatres and geriatrics have less thermoregulation) Extrinsic(external) factors that CAN be altered: drug selection (some cause more vasodilation than others), ambient temperature, duration of GA - longer procedure = colder, degree of shaving and type/volume of surgical scrub

Question 46

How might we monitor core body temp?

Answer 46

know temp BEFORE pre-meds From time of induction, monitor every 15m until patient is recovered after recovery, monitor every 30m until patient can sustain temp >37.4 methods: esophageal thermometer - most accurate Rectal thermometer - most convenient Axillary/ear is not accurate enough

Question 47

What is the normal temperatures for a dog, cat, horse and bovine?

Answer 47

Dog: 37.5-39.5 Cat: 37.5-39.5 Horse: 37.0-38.5 Bov: 37.8-39.2 Expect a slight drop in body temperatures 36-38 - allowable range under GA >38.4 - patient can allow own temp; do not heat 36-37 - must provide active heating support <36 - must inform DVM <33 - dying

Question 48

What are the complications from low body temp?

Answer 48

1. prolongs anesthetic recovery and general recovery (especially in cats) 2. predisposes patient to anes overdose - due to dec metabolism of drugs and can maintain cool patients on lower anes dose 3. shivering during recovery will increase O demands 4. below 33, brainstem is depressed and there is cardiac malfunction

Question 49

How could we minimize heat loss during GA?

Answer 49

stabilize room temp prior to premed (turn up heat, especially in winter) Prudent use of alcohol and scrub water (don't drown your patient; remove excess scrub/alcohol) Place barrier btw patient and table top Warm IV fluids to ~37.5, same for saline used for abdominal flushes Blankets, circulating warm water blanket; forced warm air blanket (bair huggers), warm water bottles minimize surgical and GA times

Question 50

What are some heating items to avoid?

Answer 50

electric heating pads and lamps - poor control and get too fast, sedated/anes 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 its too hot)> vasodilation of surface capills > cooled blood from surface goes to core and drops temp further

Question 51

What is hyperthermia under GA?

Answer 51

>39C, most often seen just before/during recovery Common causes: excessing external heat source (too much warming), cat that reacts to mu-agonists (hydromorphone, fentanyl), malignant hyperthermia (rare, more common in pigs) Management: remove heat source; fans, reverse drug if possible, cold iv fluids, turn up 100% O flow

Question 52

What are some factors that cause hypoxia

Answer 52

decreased RR and tidal volume occur w/ mu-agonists, A2 agonists (all species but severe in ruminants), ALL GA Propofol, alfaxalone cause induction apnea iso suppresses CO2drive depressed ventilation results in less O uptake and decreased CO exhaustion also dec ability to move O and CO around body

Question 53

How can we give O support?

Answer 53

patients under GA require a minimum of 33 O to maintain O saturation of blood room air is 21% O; not sufficient to meet tissue demands whenc combined w/ depressed resp function must have 100% O source to achieve maximum O saturation of blood

Question 54

How might weight affect respiratory function?

Answer 54

tidal volume already decreased under GA Increased weihgt requires more effort to expand and expel lungs; especially if animal is recumbent - dependant lung areas ("down" side of patient in lateral) mayd develop atelectasis where they'll partially collapse in area due to poor inflation Applies to morbidly obese animals and LA may require manual/automatic ventilation

Question 55

WHat do we need to be aware of with our favorite breed, the brachycephalics

Answer 55

risk of soft palate collapse. If anim also has stenotic nares, entire airway could be cut-off watch for resp distress, inc lethargy, cyanosis continuous monitoring from time of sedation until completely recovered worst risk is sedation and recovery (ie. 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 anim can pull it out on their own be aware, patient may also have collapsing trachea and size ETT appropriately

Question 56

What is normal BP with no meds?

Answer 56

120/80 (94) - varies with age, species, health status and situation

Question 57

What combination maintains BP?

Answer 57

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

Question 58

What is our BP under GA?

Answer 58

always a drop under GA degree of hypotension depends on drugs used (inhalants, acepromazine, A2's), patient stability (underlying CV/renal dz, hydration, geriatrics and neonates), duration of GA Any blood loss will contribute to hypotension

Question 59

WHat are some factors causing hypotension in anesthetized patients?

Answer 59

1. decreased cardiac function 2. vasodilation 3. evaporative losses 4. perioperative hemorrhage

Question 60

How does decreased cardiac function and Evaporative affect hypotension in anesthetized patients?

Answer 60

Dec cardiac func: dec HR + cardiac output, less V of blood moved per unit time, most severe depression by A2-agonists, inhalants and injectable anes, if severe enough can cause cardiogenic shock EVAPORATIVE: open body cavities, dry gases, real loss of fluid volume

Question 61

How does vasodilation and perioperative hemorrhage affect hypotension in anesthetized patients?

Answer 61

VASODILATION: inhalant anesthetics, acepromazine, causes a relative dec in fluid V; w/ time, fluid moves from interstitial space to vascular space - if severe enough, could result in vasogenic shock PERIOP HEMORR: can be minimal to severe, real loss of fluid volume

Question 62

What are the benefits of IV catheterization?

Answer 62

best to IV catheterize patients under heavy sedation and/or GA 1. can deliver IV fluids to maintain blood volume + support BP 2. Can be hard to place IV later bc of low BP 3. Rapid admin for emerg drugs 4. used to admin CRI's 5. Reduce risk of perivascular injection 6. Can admin a # of IV drugs one after another w/ flushing btw each one to dec trauma

Question 63

What are some acceptable values under GA for BP. When must we report?

Answer 63

Ideal values: D/C 110-160/50-70 (60-90) Eq: >80/>50 (60-90) Report: D/C systolic <90; MAP <70;diastolic <40 Eq: systolic <90; MAP <80: diastolic <40

Question 64

What are surgical fluids?

Answer 64

amount of fluids req to maintain BP in the presence of drugs that cause cardiac depression and vasodilation Always recommended

Question 65

How long do we give surgical fluids? what must we record?

Answer 65

isotonic crystalloids (LRS, normosol, plasmalyte) appropriate for most admin IV cath from time of induction > recovery - any dehydrated is correct BEFORE GA, return to appropriate maintenance after recovery to prevent fluid overload Must record fluid type, rate, total V (or start and stop times), any changes in fluid rate at they occur

Question 66

What is the surgical fluid rate in otherwise healthy patient in cats, dogs and LA?

Answer 66

Cat: 2-3ml/kg/h Dog: 3-5ml/kg/h LA: 5-10ml/kg/h Rate is used on its own Adjust w/ changes in BP, lung sounds, HR, bleeding know THIS for exam purposes

Question 67

What is a fluid bolus?

Answer 67

given when patients are hypotensive (despite surgical fluid rate) or bleeding profusely ex. when the surgical fluid rate is not enough Start w/ a SINGLE crystalloid boilus - 10ml/kg over 15m, can repeat up to 3-4 times if necessary check w/ vet before administering

Question 68

What are some reasons for surgical fluids?

Answer 68

offsets causes of hypotension (vasodilation and dec 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 elyte and acid-base imbalances (commonly occur under GA and w/ pathology) Supports renal drug elim

Question 69

What is volume overload?

Answer 69

can occur from too much fluid (excessive total volume infused or too fast fluids - giving fluids too fast prevents them from entering into the extracellular fluid V properly Given the appropriate rate and volume to the wrong patient HCT <20, low albumin, patients <5kg, heart failure, renal dz

Question 70

What are the physiological effects of volume overload?

Answer 70

1. hypertension -vry bad if pre-existing heart dz; causes heart to work harder and can cause cardiac overload - inc blood loss 2. fluids move to 3rd spaces in the body (abdomen, pleural space, pulmon spaces) - pulmonary/cerebral edema 3. can dilute O carry capacity of blood

Question 71

What are the signs of fluid overload?

Answer 71

inc lung sounds/crackles inc RR and dyspnea coughing and restlessness if patient is awake Tachycardia inc BP hemodilution (dec relative PCV) ocular and nasal discharge, chemosis SQ edema neuro signs

Question 72

How can we prevent volume overload?

Answer 72

know your calculations use appropriate-sized fluid bag (100ml for cat spay) clamp off line when transporting patients check IV line and rate hourly. caution: most drip sets will alter rate slowly over time ideally, use an infusion pump, monitor equipment, monitor patient

Question 73

How do we treat volume overload?

Answer 73

no definitive therapy maintain txs: discontinue fluids, start on diuretics, provide O support best to prevent rather than tx

Question 74

What are some tips on fluid calculations?

Answer 74

1. convert weight to kgs 2. Calculate hrly rate - ml/h (SA); L/h (LA) and ALWAYS enter this value into medical notes 3. then, calculate drip rate from above in whole drops per whole seconds Drip sets: >10-15kg: 10drop/ml, <10kg: 60gtt/ml set (aka. pediatric set) 4. Double check 3's, make sure they make sense. Ex. neger give 50ml/hr to a cat 5. mark fluid bag w/ start/end for total volume infused 6. be aware that certain patients have altered rate. heart/renal may need dec fluid rates; fever in yg animals req high rates. in doubt, ask