Patient evaluation

Question 1

What are the goals for ‘safe anesthesia?’

Answer 1

1. Allow surgical/medical procedures to be performed with minimal risk to life or HEALTH to the paitent
2. Lack of mortality and lack of morbidity (impaired organ function; other complications)

Question 2

What is safe anesthesia (5)?

Answer 2

1. Good pre-anesthetic evaluation
2. Adequate preparation and anticipation of possible problems
3. Vigilant monitoring through recovery
4. Knowledge of the physiologic parameters of the cardiovascular/respiratory systems
5. Knowledge of the pharmacodynamic effects of the agents used

Question 3

T/F: There is no safe anesthetic; only safe anesthetists.

Answer 3

TRUE

Question 4

What are the 5 main mortality/morbidity risk factors in anesthesia?

Answer 4

1. Concurrent disease
2. Advanced age
3. Extreme weight
4. Emergency procedures and after hours
5. Human error (poor pre-op and post-op patient care, inadequate monitoring, inadequate teamwork, disorganization/poor communication)

Question 5

T/F: Over half of anesthesia-related deaths occur within 0-3 hours post-op.

Answer 5

TRUE

Question 6

What 6 things are included in the pre-anesthetic patient evaluation?

Answer 6

1. Signalment and general appearance and attitude
2. Pertinent history
3. Physical exam and accurate wt.
4. Risk assessment (ASA physical status)
5. Pre-anesthetic work-up
6. Preparation

Question 7

What does the pre-anesthetic work-up depend on? What is included?

Answer 7

Physical status

Reason for anesthesia Blood work; radiology; ECG or echo if necessary

Question 8

How much fat does ideal weight contain?

Answer 8

20%

Question 9

What must you do to avoid overdosing an overweight animal?

Answer 9

Estimate ideal weight for drug dosages–esp. IV induction drugs; central compartment close to ‘normal’

Question 10

T/F: Thiopental, propofol are very lipophilic–slowly redistributed–>decreased Vd in obese

Answer 10

FALSE–they are rapidly redistributed–>increased Vd in obese

Question 11

T/F: Premeds are best given IM rather than IV.

Answer 11

FALSE–best given IV rather than IM (low blood flow in fat)

Question 12

What are some concerns in overweight/obese animals?

Answer 12

1. Cardiac output increased–increased blood volume; contributes to volume overload with cardiac disease
2. Decreased lung and chest wall compliance
3. Decreased functional residual capacity (FRC) excess fat and volume impinging thorax–involved in gas exchange –> resp. depression (low tidal vol; inc. CO2; mechanical ventilation necessary)

Question 13

T/F: Certain positions can compromise pulmonary function.

Answer 13

TRUE–it can impede adequate ventilation even in lean patients

Question 14

What should you do before anesthetizing an extremely thin/cachectic patient? What concerns exist?

Answer 14

• Investigate for underlying disease
• IV anesthetics–distributed from the plasma to VRG, then to muscle and fat
  
  • No fat = drugs stay in VRG longer
  • Careful administration–titrate to effect
• Prone to severe hypothermia

Question 15

Why is size important when anesthetizing tiny patients (4)?

Answer 15

1. The tiny can get very cold
2. Accurate weight to avoid overdose of drugs/fluids (use fluid pump to avoid accidental overdose)
   
   1. Use appropriate size syringes–think about dilution of induction drugs for titration
3. Patient difficult/impossible to access under drapes
   
   1. Make sure catheter is accessible
4. May often be prone to hypoglycemia

Question 16

Why does size matter when anesthetizing large breeds (3)?

Answer 16

1. Giant breeds–profound response to sedatives (acepromzaine)–slower metabolic rate
2. Smaller body surface area (BSA) to body weight ratio–reduce dosage rate or dose to BSA
3. Senescence occurs earlier so life expectancy lower

Question 17

How does age affect anesthesia (specifically young/old)?

Answer 17

• Neonatal (anesth common in large animals)–weeks/month–pediatric (depends on breed)
  
  • Increased sensitivity to drug effects
  • Hypothermia
  • Avoid hypoglycemia (BBB less developed)
• Geriatric (~>75% of life span)
  
  • Generally, decreased organ reserves; sub-clinical dysfunction
• In general; dosages will be altered and certain drugs might be avoided

Question 18

What must you keep in mind when anesthetizing brachycephalics?

Answer 18

• Elongated soft palate, everted saccules; obstructed nares–> prone to upper airway obstruction
  
  • Vigilant observation when sedated and after extubation
• High vagal tone predisposes to bradycardia

Question 19

What should be kept in mind when anesthetizing greyhounds?

Answer 19

• High energy/highly stressed
  
  • Susceptible to stress hyperthermia
    
    • Temp can go up to 105 post-surgery
  • Good sedation desirable
• Lack of fat–> IV anesthetics stay in VRG longer
  
  • Avoid thiobarbiturates
• Sleep times longer (propofol) and pharmacokinetics differ from non-grehyounds–not just because of lack of fat
  
  • Thiobarbiturates (NOT oxybarb or methylatedoxybarb)
  • Decreased ability to metabolize drugs via P450 family of enzyme pathways

Question 20

What should be kept in mind when anesthetizing herding breeds?

Answer 20

• Multidrug resistance gene (MRDI) mutation
• MDRI gene code for p-glycoprotein (drug transport pump that limits drug absorption, distribution/excretion–particularly from brain which may lead to drug toxicity): some breeds have mutation
  
  • Ivermectins; anti-cancer; anti-diarrhea
  • Acepromazine; butorphanol
    
    • Avoid large dosages to avoid prolonged effects

Question 21

Which breeds have a predisposition for cardiomyopathy? What should you do?

Answer 21

• Boxer
• Doberman pincher
• Giant breeds
• Maine coon cat
• Careful ascultation–if murmur or dysrhythmia heard further workup warrented (radiography/echocardiogram/ECG)

Question 22

What cardiac/renal disease medications potentiate anesthesia-related C/V depression?

Answer 22

• Angiotensin converting Enz inhibitors
  
  • Maybe best to avoid acepromazine
• Beta or Ca channel blockers

Question 23

What conditions/medications cause an impediment to the patients’ ability to handle stress response?

Answer 23

• Hypoadrenalcorticism (Addison’s)
• Treatment for Cushing’s (mitotane, trilostane) or sudden termination of long-term corticosteroids

Question 24

What are some common drug interactions that should be considered before anesthetizing patients?

Answer 24

• Serotonin reuptake inhibitors, tricyclic antidepressants; MAO inhibitors
  
  • Interactions with tramadol
  • Some opioids (serotonin syndrome)
• Phenobarbitol–P450 inducer–increases metabolism of other drugs metabolized similarly
• Herbal medicines

Question 25

Why is the anesthesia history of a patient important?

Answer 25

* Previous anesthesia problems? * If available, always review previous anesthesia record * Prolonged or stormy recovery * Hypotension; bradycardia; dysrhythmia? * Patient may/may not repeat--may/may not use the same protocol * May give sedative before recovery to avoid another stormy recovery

Question 26

Physical exam before anesthesia

Answer 26

* Need not be as complete as the general exam *if already performed by the primary clinician* * Still, anesthetist **must** perform own PE * Should be done the day of/before anesthesia * Can be done in less than 5 minutes

Question 27

What is included in the physical exam by the anesthetist?

Answer 27

* Attitude--BAR or depressed? * MM--color/refill * Hydration--dry/moist mm; skin turgor * Cardiac/thoracic auscultation--normal or heart murmur? * Dysrhythmia? * Brady/tachycardia? * Character of breathing--normal or polypneic? * Abdominal component? * Lung sounds--clear or crackles? * Evidence of pain? * Determine ASA physical status

Question 28

Risk assessment--ASA physical status

Answer 28

* Based on the classification set by the American Society of Anesthesiologists * Based on the physical status of the patient at the time of presentation for anesthesia * Somewhat objective * Some consider surgical/procedural risk--highly invasive procedures (lung, cardiac, or neuro) * Emergency and after hours increase risk (personnel may be diminished in quantity/quality)

Question 29

What are the different ASA physical status classifications?

Answer 29

Question 30

Why are ASA classifications important?

Answer 30

* To manage cases consistent with that classification * ASA I or II likely will not require invasive monitoring, extra IV catheters, dif. kinds of drug protocol * *Generally*, no drug contraindications * ASA III-IV would likely not be managed with same protocol or dosages and management as a healthy OHE * Classifications allow for grouping of cases for scientific study

Question 31

T/F: Additional information such as hematology and blood chemistries usually required but vary depending on condition, age of patient.

Answer 31

TRUE

Question 32

T/F: Studies have found that pre-anesthetic lab work is a good predictor of risk and often alters anesthetic protocol management

Answer 32

FALSE--pre-anesth lab work is NOT a predictor of risk and RARELY alters antesthetic protocol management

Question 33

What are the lab/diagnostic general recommendations for the following: Healthy (ASA I-II) ≤ 5-7 yr Healthy \> 5-7 yr; and especially aged Systemic disease--any age Thoracic rads; ultrasound; ECG; echocardio; etc.

Answer 33

* Healthy ≤ 5-7 yr * PCV; TP; BUN or creat; glu; urine SpG * Healthy \> 5-7 yr * CBC; chemistries * Systemic disease * CBC; chemistries +/- coag profile * Thoracic rads, US, etc. * Depends on disease

Question 34

What are the fasting guidelines for dogs/cats?

Answer 34

* Generally 12 hr fast (no food after 10pm) but **water always** (some say fast 8 hrs) * May be longer if endoscopy or GI sx * Neonates/pediatrics should receive supplemental glucose-containing liquids or soupy food up to 4-6 hrs prior * Diabetics require adjustment in insulin dose (usually half usual dosage) and procedure done early morning

Question 35

What are the fasting requirements for large animals?

Answer 35

* Equine * No grain for 12 hr * Most recommend no hay 8-12 hr but some will allow hay 4-6 hr * Water always * Full stomach needs to be avoided * Ruminants * No food 18-24 hrs * No water 12-18hr * Smaller ruminants, calves * No food 12-18 hrs * No water 8-12 hrs

Question 36

Which animals should **not** be fasted prior to anesthesia?

Answer 36

* Mice * Rabbits * Birds * Guinea pigs

Question 37

Why is fasting prior to anesthesia important?

Answer 37

* If patient vomits/regurgitates after/during induction--pulmonary aspiration of particulate material = BAD * Liquid not good either * Regurgitated or refluxed liquid during anesthesia not uncommon * Reason for intubation with a cuffed and adequately inflated endotracheal tube

Question 38

Vomiting w/ anesthesia

Answer 38

* Vomiting = active process (retching) expulsion of stomach contents--very common only after premed opioid administration * Usually not a problem in healthy animals * Avoid in animals at great risk for aspiration * Ex: dilated esophagus; laryngeal paralysis; recumbent, somnolent

Question 39

T/F: Post-operative nausea/vomiting (PONV) is very common in humans, but is not common in veterinary paitents--in the recovery period.

Answer 39

TRUE

Question 40

T/F: Fasting does NOT decrease incidence regurgitation or reflux.

Answer 40

TRUE

Question 41

Regurgitation/reflux during anesthesia

Answer 41

* Regurgitation = passive process--material from esophagus (or stomach) into oral cavity * More common in animals with upper GI disease and other less common disease processes--dilated esophagus, etc. * *Rapid induction and intubation important* * Regurgitation during anesthesia is not uncommon--evident in mouth or on table * Lavage esophagus with water then suction * Silent reflux (into esophagus) * ~38% healthy dogs reflux during anesthesia (detected w/ esophageal pH probe)--variety of drugs and fasting times * May result in esophagitis (or worse--esophageal stricture)

Question 42

During preparation, what should be done to anticipate possible complications/problems and be prepared to manage them?

Answer 42

* Pre-calculated dosage rates for emergency drugs * Suspect difficult intubation? Prepare extra T tubes/stylets * Suspect excessive blood loss? Blood available; extra IV catheter * Make certain that catheter is accessible under drapes (extension tubing if necessary)

Question 43

T/F: Device protocol is standardized across all patients

Answer 43

FALSE * One does not fit all * Tailored to the patient based on physical signs and status * Monitoring techniques may also depend on patient

Question 44

What specific knowledge should you have in order to be fully prepared when anesthetizing your patient?

Answer 44

* Be knowledgeable of the drugs you are using * Know what they do to the patient * Are they appropriate for that patient? * Working knowledge of the normal physiologic parameters--and recognize abnormal

Question 45

Why have an anesthesia record?

Answer 45

* Allows trends of the parameters of vital signs to be followed * Observed problems and any corrective measures are recorded * Becomes permanent part of animal's record--referred to for future anesthesia * Legal document * Fulfills the important requirements of good practice standards