Patient evaluation Flashcards
What are the goals for ‘safe anesthesia?’
- Allow surgical/medical procedures to be performed with minimal risk to life or HEALTH to the paitent
- Lack of mortality and lack of morbidity (impaired organ function; other complications)
What is safe anesthesia (5)?
- Good pre-anesthetic evaluation
- Adequate preparation and anticipation of possible problems
- Vigilant monitoring through recovery
- Knowledge of the physiologic parameters of the cardiovascular/respiratory systems
- Knowledge of the pharmacodynamic effects of the agents used
T/F: There is no safe anesthetic; only safe anesthetists.
TRUE
What are the 5 main mortality/morbidity risk factors in anesthesia?
- Concurrent disease
- Advanced age
- Extreme weight
- Emergency procedures and after hours
- Human error (poor pre-op and post-op patient care, inadequate monitoring, inadequate teamwork, disorganization/poor communication)
T/F: Over half of anesthesia-related deaths occur within 0-3 hours post-op.
TRUE
What 6 things are included in the pre-anesthetic patient evaluation?
- Signalment and general appearance and attitude
- Pertinent history
- Physical exam and accurate wt.
- Risk assessment (ASA physical status)
- Pre-anesthetic work-up
- Preparation
What does the pre-anesthetic work-up depend on? What is included?
Physical status
Reason for anesthesia Blood work; radiology; ECG or echo if necessary
How much fat does ideal weight contain?
20%
What must you do to avoid overdosing an overweight animal?
Estimate ideal weight for drug dosages–esp. IV induction drugs; central compartment close to ‘normal’
T/F: Thiopental, propofol are very lipophilic–slowly redistributed–>decreased Vd in obese
FALSE–they are rapidly redistributed–>increased Vd in obese
T/F: Premeds are best given IM rather than IV.
FALSE–best given IV rather than IM (low blood flow in fat)
What are some concerns in overweight/obese animals?
- Cardiac output increased–increased blood volume; contributes to volume overload with cardiac disease
- Decreased lung and chest wall compliance
- 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)
T/F: Certain positions can compromise pulmonary function.
TRUE–it can impede adequate ventilation even in lean patients
What should you do before anesthetizing an extremely thin/cachectic patient? What concerns exist?
- 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
Why is size important when anesthetizing tiny patients (4)?
- The tiny can get very cold
- Accurate weight to avoid overdose of drugs/fluids (use fluid pump to avoid accidental overdose)
- Use appropriate size syringes–think about dilution of induction drugs for titration
- Patient difficult/impossible to access under drapes
- Make sure catheter is accessible
- May often be prone to hypoglycemia
Why does size matter when anesthetizing large breeds (3)?
- Giant breeds–profound response to sedatives (acepromzaine)–slower metabolic rate
- Smaller body surface area (BSA) to body weight ratio–reduce dosage rate or dose to BSA
- Senescence occurs earlier so life expectancy lower
How does age affect anesthesia (specifically young/old)?
- 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
What must you keep in mind when anesthetizing brachycephalics?
- 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
What should be kept in mind when anesthetizing greyhounds?
- High energy/highly stressed
- Susceptible to stress hyperthermia
- Temp can go up to 105 post-surgery
- Good sedation desirable
- Susceptible to stress hyperthermia
- 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
What should be kept in mind when anesthetizing herding breeds?
- 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
Which breeds have a predisposition for cardiomyopathy? What should you do?
- Boxer
- Doberman pincher
- Giant breeds
- Maine coon cat
- Careful ascultation–if murmur or dysrhythmia heard further workup warrented (radiography/echocardiogram/ECG)
What cardiac/renal disease medications potentiate anesthesia-related C/V depression?
- Angiotensin converting Enz inhibitors
- Maybe best to avoid acepromazine
- Beta or Ca channel blockers
What conditions/medications cause an impediment to the patients’ ability to handle stress response?
- Hypoadrenalcorticism (Addison’s)
- Treatment for Cushing’s (mitotane, trilostane) or sudden termination of long-term corticosteroids
What are some common drug interactions that should be considered before anesthetizing patients?
- 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
Why is the anesthesia history of a patient important?
- Previous anesthesia problems?
- If available, always review previous anesthesia record
- Prolonged or stormy recovery
- Hypotension; bradycardia; dysrhythmia?
- If available, always review previous anesthesia record
- Patient may/may not repeat–may/may not use the same protocol
- May give sedative before recovery to avoid another stormy recovery
Physical exam before anesthesia
- 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
What is included in the physical exam by the anesthetist?
- 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
Risk assessment–ASA physical status
- 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)
What are the different ASA physical status classifications?
Why are ASA classifications important?
- 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
- ASA I or II likely will not require invasive monitoring, extra IV catheters, dif. kinds of drug protocol
- Classifications allow for grouping of cases for scientific study
T/F: Additional information such as hematology and blood chemistries usually required but vary depending on condition, age of patient.
TRUE
T/F: Studies have found that pre-anesthetic lab work is a good predictor of risk and often alters anesthetic protocol management
FALSE–pre-anesth lab work is NOT a predictor of risk and RARELY alters antesthetic protocol management
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.
- 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
What are the fasting guidelines for dogs/cats?
- 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
What are the fasting requirements for large animals?
- 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
Which animals should not be fasted prior to anesthesia?
- Mice
- Rabbits
- Birds
- Guinea pigs
Why is fasting prior to anesthesia important?
- 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
Vomiting w/ anesthesia
- 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
T/F: Post-operative nausea/vomiting (PONV) is very common in humans, but is not common in veterinary paitents–in the recovery period.
TRUE
T/F: Fasting does NOT decrease incidence regurgitation or reflux.
TRUE
Regurgitation/reflux during anesthesia
- 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
- More common in animals with upper GI disease and other less common disease processes–dilated esophagus, etc.
- 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)
During preparation, what should be done to anticipate possible complications/problems and be prepared to manage them?
- 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)
T/F: Device protocol is standardized across all patients
FALSE
- One does not fit all
- Tailored to the patient based on physical signs and status
- Monitoring techniques may also depend on patient
What specific knowledge should you have in order to be fully prepared when anesthetizing your patient?
- 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
Why have an anesthesia record?
- 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
