Lecture 2: Patient Evaluation & Preparation

Who should perform the pre-anesthetic evaluation?

the veterinarian in charge of the patient

What is part of the pre-anesthetic evaluation?

• signalment

• history (medications, vaccines, preventatives, symptoms/severity/how long if patient is ill)

• PE (including BW, BCS)

• All necessary diagnostics

• Temperament/mentation and level of pain and stress

What patients should have routine ECG screening?

• patients with evidence of CV disease

• geriatric patients

• underlying disease that may lead to arrhythmias: hyperkalemia, GDV, splenomegaly, traumatic myocarditis

During your pre-anesthetic PE, what important vitals are you evaluating?

• temp

• pulse (rate, rhythm, and quality: make sure to auscultate and palpate pulse

• respiration (include trachea)

• mm/CRT

• body wt (in kg)

What clinical signs are seen in 5-6% and 6-8% dehydration?

5-6%: subtle loss of skin elasticity

6-8%: definite delay in return of skin to normal position, slight prolongation of CRT, eyes possibly sunken in orbits, possibly dry mm

What clinical signs are seen in 10-12% and 12-15% dehydration?

10-12%: tented skin stands in place, definite prolongation of CRT, eyes sunken in orbits, dry mm, possibly sign of shock

12-15%: definite signs of shock (tachycardia, cool extremities, rapid and weak pulses), death imminent

What pre-anesthetic testing should be done on a young (< 5 y/o) healthy patient having an elective procedure with no abnormal history?

PCV/TS/Glucose/BUN (“big 4” or “QATS”)

What pre-anesthetic testing should be done on older patients having an elective or non-elective procedure; any hx of recent illness; screening for suspected infectious disease in endemic region?

CBC/Chemistry profile/UA (“minimum database”) ± T4, ECG, blood pressure, thoracic rads, echocardiogram, blood gas analysis, coag profile, liver function testing, 4Dx, etc

What pre-anesthetic tests & diagnostics should be run, besides labs?

• blood pressure

• stress test/exercise intolerance

• breathing vs cardio

Where is the pre-anesthetic evaluation performed?

typically in clinic, but also done during farm/house calls and in a quiet area to better auscultate heart and lungs

When should pre-anesthetic evaluations be performed?

usually the day before or up to 1 week before a planned procedure and another short exam done the day of (in emergency cases, done immediately prior to procedure)

Why should a pre-anesthetic evaluation be done on all patients?

• greater chance of a safe anesthetic episode and/or a more successful outcome for the patient

• formulate an assessment of the patient’s overall function of perioperative risk

• provide the client with valuable information that will help them decide if they are willing to take the risk (convo should take place and be documented prior to sedating/anesthetizing any patient)

What is a category I physical status patient and give clinical examples?

normal healthy patients → OVH, castration, ear/tail docking, declaw

What is a category II physical status patient and give clinical examples?

patients with mild systemic disease → skin tumor, fracture, local infection, compensated cardiac disease, well-controlled diabetic, uncomplicated hernia, pregnant, obese

What is a category III physical status patient and give clinical examples?

patient with severe systemic disease → fever, dehydration, anemia, cachexia, mod. hypovolemia, uncontrolled DM, COPD, renal failure

What is a category IV physical status patient and give clinical examples?

Patient with severe systemic disease that is a constant threat to life → Uremia, toxemia, sepsis, shock, severe dehydration, cardiac decompensation or failure, emaciation, high fever

What is a category V physical status patient and give clinical examples?

Moribund patients not expected to survive without operation → Extreme shock and dehydration, terminal malignancy or infection, severe trauma

What is the physical status of a patient?

• presence or absence of disease (determined by hx, PE, labs, and other diagnostics)

• severity of pain if present

• level of stress and behavior

• overall efficiency and function of organ systems

When should the ASA physical status be assigned?

after the PE is complete and the lab work or diagnostic tests have been interpreted

A 3 y.o. male intact Beagle presents to your clinic on emergency for a laceration over the right flank region after getting tangled in barbed wire. The laceration is about 4 inches long and will require cleaning the wound, placing a penrose drain, and surgical closure of the remainder of the wound. The remainder of the PE is within normal limits. The owner says the dog is up to date on vaccines, flea/tick preventative, and heartworm medication.

PCV/TS = 37%/6.4 g/dL

T= 101.4◦ F

P = 110 bpm

R = 32 bpm

What is the ASA physical status?

I-IIE

“Miss Molly” 12 y.o. Quarter Horse mare referred to the university teaching hospital for colic of 12 hours duration. Trainer gave a dose of Banamine (flunixin meglumine 500 mg, IV). She is 9 months pregnant. Pawing and rolling intermittently

Physical exam:

◦ Tachycardia (72 bpm)

◦ Tachypnea and increased effort (24 bpm)

◦ Distended abdomen, no gut sounds

◦ Mucus membranes are dark pink, CRT = 3 sec

◦ PCV/TS = 55%/5.8 g/dL

◦ Abdominocentesis = dark yellow, TP = 5 g/dL, WBC 20,000/µl

◦ Abd U/S = distended loops of SI which is confirmed on rectal exam

What is the ASA physical status?

IVE

Why is ASA physical status important?

• used to assess “anesthetic risk” of a case

• physical status effects the PK and PD and aids the selection of drugs and/or techniques for a patient

• knowledge of what could happen helps us plan

• can also be used from a legal standpoint, retrospectively

The sicker the patient = the poorer the physical status = increased likelihood of ___________.

cardiopulmonary emergencies

Other than physical status, what are the other considerations for dosing drugs?

• species (pharmacogenetics)

• size of patient (smaller animals will require a higher dose per unit of body weight)

• obesity (volume of distribution for drugs)

• poor condition/starvation

• age (metabolic rate)

How should the dosing of anesthetic drugs be altered for neonate/pediatric, juvenile to early adulthood, and geriatric patients?

neonate/pediatric: decrease dose

juvenile to early adulthood: increase dose

geriatric: decrease dose

What concurrent medications could cause problems during the peri-anesthesia episode?

• Aminoglycosides, ACE Inhibitors

• Digoxin, Beta blockers, Diuretics

• NSAIDs, Tramadol if patient is taking MOA inhibitor, TCA or PPA, Opioids

• Selegiline (MOA inhibitor), Clomipramine (TCA)

• Phenylpropanolamine (PPA), Pseudoephedrine, Phenobarbital

• Chemotherapy drugs, Sulfonimides

• Nutraceuticals: St. John’s wort

How should a patient be prepared for anesthesia?

• possible fasting

• hygiene and patient comfort: encourage defecation/urination prior to surgery, bathe excessively dirty patient prior (clean out hooves), parasite control

• correct dehydration and electrolyte imbalance

• preoperative antibiotics

• patient specific prep (behavior, pain, nausea, cough)

How long should canine and feline patients be fasted prior to anesthesia?

food: 6-12 hr

water: up until premed given

How long should equine vs cattle patients be fasted prior to anesthesia?

equine

food: 4-12 hrs

water: up until premed given

cattle

food: 18-24 hrs

water: 12-18 hrs

How long should small ruminants, calves, and camelid patients be fasted prior to anesthesia?

food: 12-18 hr

water 8-12 hr

How long should swine and avian patients be fasted prior to anesthesia?

swine: 12-24 hr

bird: 4-6 hr

(water not deprived)

What patients do not have necessary fasting and water deprivation times?

rodents and rabbits, birds < 200g, and neonates

Why is a patient fasted prior to general anesthesia?

• decrease food and fluid in stomach

• decrease risk of aspiration

• distended stomach or rumen impairs ventilation and could lead to hypoxemia and hypercapnia

• in horses, a full stomach could rupture at induction

Why is it not necessary for neonates, small birds, and some mammals to be fasted prior to general anesthesia?

• prone to hyperglycemia within a few hours of starvation

• increased metabolic rate in birds and small mammals

What has been shown to reduce the incidence of gastroesophageal reflux in dogs post-anesthesia?

feeding a small amount of canned food (half of daily amount) 3 hours prior to anesthesia

What are the 4 H’s of general anesthetic concerns?

1. hypotension

2. hypoventilation

3. hypothermia

4. hypoxemia

What are the species, age, disease, or procedure specific general anesthetic concerns?

• Hemorrhage

• Pain

• Delayed recovery

• Regurgitation

• Laryngeal spasm

• Difficult intubation

• Dysphoria

• Arrhythmias

• Myopathy or neuropathy