1/2: Intro & Patient Evaluation Flashcards
What is anesthesia?
Loss of sensation to all or part of the body
Anesthetic drugs depress _____ _____ locally, regionally, and centrally.
nervous tissue
What is general anesthesia (2 definitions)?
Drug-induced unconsciousness;
Controlled/reversible depression of CNS and perception
What are the 5 requirements for surgical GA?
- Unconsciousness (hypnosis, narcosis)
- Amnesia
- Muscle relaxation
- Lack of pain perception
- Suppression of reflexes (motor, autonomic)
What is pain?
Unpleasant sensory/emotional experience associated with actual/potential tissue damage
What is analgesia?
Absence of pain in response to painful stimulus;
Patient may be unconscious
What is nociception?
Physiologic process underlying pain perception;
Neural encoding process of stimuli;
Does not require consciousness (i.e. can occur during GA)
T/F: pain perception can still occur during GA
True
What is local anesthesia? Example?
Loss of pain sensation to a body area (i.e. dental block)
What is regional anesthesia? Example?
Loss of pain sensation to larger body area (i.e. epidural)
What is balanced anesthesia and what are some things that it targets?
Use of multiple drugs/techniques targeted to specific components (amnesia, muscle relaxation, anti-nociception, autonomic reflexes)
What is a specific example of balanced anesthesia?
Using low dose ketamine with low dose propofol;
Ketamine increases HR while prop decreases HR
What are 6 factors that can increase anesthetic risk?
- Major vs. minor procedures
- Major organs
- ER procedures
- Duration of anesthesia/surgery
- Anesthetic choice/manner given
- Human error
What length procedures have higher risk for adverse outcome and why?
Longer procedures due to increased tissue handling
Which anesthetic risk results in the highest number of human deaths?
Human error
Regarding anesthetic risk, there are no safe _____, only safe _____.
anesthetic procedures, anesthetists
What 3 things correlate with a higher mortality risk?
- Increased physical status of patient
- Increased age
- Emergency situations
According to Brodbelt et al 2008, what is the risk (%) of anesthetic sedative-related death in dogs? Cats? Rabbits?
Dogs = 0.17%
Cats = 0.24%
Rabbits = 1.39%
According to Brodbelt et al 2008, what type of patient in general is going to have a higher risk of anesthetic-related mortality?
sick (as opposed to healthy)
In order from highest to lowest risk, what was the anesthetic risk for sick animals in Brodbelt et al 2008?
Rabbit (7.37% > Cats (1.4%) > Dogs (1.33%)
In general, at what phase of a procedure do we see the highest risk for mortality?
Post-op (0-3 hours)
Why do we see a high risk of mortality 0-3 hours post-op?
Lack of observation and lack of O2 support
What is the overall anesthesia-related mortality in horses?
1%
Including obstetric/colic patients, what is the mortality rate in horses?
10%
What are the 2 most common reasons for mortality in horses undergoing a procedure?
Cardiac arrest, recovery injury (this is really due to euthanasia)
Horses have a ___ fold mortality rate over dogs/cats.
10
Horses have a ___ fold mortality rate over humans.
100
What are some owner concerns regarding anesthesia that we need to have answers for?
- Who monitors the patient?
- What do you monitor?
- HR/rhythm, RR, MM, SpO2, BP, temp, EtCO2
- How will you manage my pet’s pain?
- Why do animals need GA when procedure can be formed awake in people?
- Are there specific spp/breed/individual concerns?
What are the 5 general steps of anesthesia?
- Pre-anesthetic evaluation
- Pre-medication period
- Induction of anesthesia (usually IV but can be IM)
- Maintenance
- Recovery
- Post-anesthetic period
What are the 12 general principles of anesthesia?
- Critical evaluation of history, PE, and lab data
- Stabilize & correct identified abnormalities, if possible, prior to anesthesia
- Be organized and efficient to minimize anesthesia time
- Select protocol based on patient, existing abnormalities, and to minimize adverse effects
- ID and prepare for potential complications
- Establish IV access whenever possible
- Secure & maintain patient airway
- Use supplemental oxygen when indicated and provide ventilatory support
- Monitor vital body systems (cardio, respiratory, CNS)
- ID and correct abnormalities that arise
- Continue monitoring and support thru recovery
- Use appropriate analgesia and sedation to minimize pain and distress
What are the 4 components to patient evaluation?
- History
- Signalment
- PE
- Labs and diagnostics
Why is a thorough history critical?
Allows evaluation of underlying disease processes (systemic effects, chronicity) and ID of other abnormalities that may affect outcome of surgery
What are 6 good questions to ask the owner regarding the patient history?
- Past medical problems?
- Previous anesthesia?
- Pet’s energy level? Tire easily/out of breath?
- Any changes in drinking/urination?
- Current meds? (Rx’ed and OTC, supplements)
- Diet, exercise, environment
Why is species an important signalment?
There are many spp differences in anesthetic management, risks, and drug selection;
Anesthetist needs working knowledge of these differences
What are brachycephalic breeds more prone to?
upper airway obstruction
What is important about Greyhounds and Collies?
drug metabolism
What breeds are predisposed to cardiac disease?
Cavaliers, Maine Coons
What are Poland China, Landrace, and Duroc pigs predisposed to?
malignant hyperthermia
What are quarter horses predisposed to?
Hyperkalemic periodic paralysis (HYPP)
What are draft horses predisposed to?
Laryngeal hemiplegia (35%)
What are 3 concerns regarding anesthesia in geriatric patients?
- Decreased organ reserve –> cardio, liver, kidney
- Decreased sedative doses
- Osteoarthritis –> positioning/padding
What are 4 concerns regarding anesthesia in pediatric patients?
- Immature liver, CV/autonomic reflexes
- Decreased drug metabolism
- Hypoglycemia
- Hypothermia
What are 2 concerns regarding anesthesia related to sex/neuter status?
- Temperament (i.e. stallions, bulls)
- Sex-related drug metabolism differences
What 3 things are important considerations regarding an aggressive/fractious, anxious, or fearful patient?
- Poses a danger to staff
- Limits pre-anesthetic examination
- Need for more potent drugs, higher doses or combos
Accurate body weight is needed for _____ _____.
drug calculations
What are 3 anesthetic concerns related to body condition score?
- Cardiopulmonary effects
- Complicated by age-related factors
- Drug doses (most should be dosed on lean body weight)
Lean body weight = _____% ideal body weight
~120-130%
In the USA, ___% of dogs and ___% of cats are obese.
55%, 53%
Worldwide, ____% of dogs are obese
>22-40%
What % of horses are obese in Great Britain? Denmark? Australia? Canada?
GB = 31.2%
Denmark = 24%
Australia = 24.5%
Canada = 28.6%
What is the scale used for BCS and what is the ideal?
9-point;
Ideal = 5/9, ~20-25% body fat
What is the BCS scale for horses called?
Henneke BCS
What does the Henneke BCS scale assess?
SQ fat deposition in 6 areas:
Crest of neck, withers, behind shoulder, over ribs, along back, around tail head
What are the 7 body systems that should be evaluated during a PE?
- General body condition, attitute, mental status
- Neuro
- Ortho
- Respiratory
- Cardio
- GI
- Genitourinary
What does an anesthesia PE focus on?
Cardio, respiratory, CNS, liver and kidney function
When should the focused anesthesia PE be done?
Only after a FULL PE
What lab data should be collected on normal healthy patients or with localized disease (<5 years old)?
Big 4: PCV, TP, azostrip, BG
What does a high TP mean? Low?
High = dehydration, chronic inflammation
Low = protein loss thru GI or kidney, decreased production (liver failure)
What is an azostrip?
Reagent strip for BUN
What lab data should be collected from geriatric dogs and cats (>5-7 years old)?
CBC, chem, UA
___% of geriatric dogs have subclinical disease identified by pre-op bloodwork
30%
What lab data should be collected on horses >12-15 years old?
CBC, chem
What is the minimum PCV for surgery?
20%
What things make up a TP?
albumin + globulins + fibrinogen
What does a decreased albumin do to anesthetic drug binding?
Decreases binding and increases their effect
What is ALT?
Alanine transaminase - “leakage enzyme”
What is ALP?
Alkaline phosphatase - relates to cholestasis
What are the 4 main biomarkers of liver function?
- BUN
- Glucose
- Albumin
- Clotting factors
How is BUN synthesized in the liver?
Protein –> ammonia –> urea
What electrolytes are important for fluid and acid base homeostasis?
Na, Cl, K, Ca
What are some additional diagnostic tests that can be performed prior to anesthesia?
- Thoracic rads
- Echocardiography
- Clotting profile
- CT, MRI, ultrasound
What can thoracic rads show us?
Pulmonary contusions, pneumothorax, diaphragmatic hernia
What can abdominal rads show us?
Urinary bladder rupture, hemoabdomen
What is an anesthetic physical status of I? Example?
Healthy, no disease;
EX: spay, neuter
What is an anesthetic physical status of II? Example?
Healthy, localized or mild systemic disease;
EX: patellar lux, CCR
What is an anesthetic physical status of III? Example?
Moderate systemic disease;
EX: murmur, anemia
What is an anesthetic physical status of IV? Example?
Severe systemic disease, life threatening;
EX: heart, liver failure
What is an anesthetic physical status of V? Example?
Moribund, not expected to live >24 hours;
EX: multi-organ failure
Anesthesia physical status is directly related to risk of peri-anesthetic _____.
death
What is the % risk of peri-anesthetic death in dogs and cats with Class I-II physical status?
0.12%
What is the % risk of peri-anesthetic death in dogs and cats with Class III-V physical status?
>40%
What is the % risk of peri-anesthetic death in horses for non-emergency procedures?
1%
What is the % risk of peri-anesthetic death in horses for emergency procedures?
2-10%
Anesthetic drugs alter normal physiology/ability to maintain _____.
homeostasis
What are examples of cases that need to proceed immediately to anesthesia and surgery?
Continued blood loss (splenic tumor rupture), acute abdomen (GDV)
What steps can be taken to stabilize a patient for surgery?
Rehydration, correction of acid base and electrolyte abnormalities, anemia, hypoproteinemia
What are the steps on the pre-emptive pain scoring system?
None, mild, moderate, severe
What are 6 things that a complete anesthetic plan addresses?
- Pre- and post-anesthetic sedation/tranquilization
- Peri-op analgesia - pre-emptive, intra-op, post-op
- Induction and maintenance drugs
- Ongoing physiologic support
- Monitoring plan
- Anticipation and response plan to adverse events or complications
An individualized anesthetic plan is _____ to allow for patient responses during anesthesia.
flexible
Why do we fast dogs and cats prior to anesthesia?
Decreased risk of regurgitation/aspiration
How long do we fast dogs and cats?
6-12 hours (3-6 may be sufficient)
How long do we fast dogs and cats up to 4 months old and why?
~4 hours due to risk of hypoglycemia
T/F: Dogs and cats cannot have water before a procedure.
False
How can we prevent peri-anesthetic nausea and vomiting in dogs?
Give Maropitant (Cerenia)
1 mg/kg SQ at least 1 hour before opioid administration
What type of drug is maropitant (Cerenia)?
Neurokinin-1 antagonist
T/F: Maropitant provides adjunct analgesia.
True
How long do we fast horses before anesthesia?
6-12 hours with access to water
Why do we fast horses if they cannot vomit?
Weight of GI contents –> increased P on diaphragm –> limits lung expansion –> decreased ventilation –> decreased arterial oxygen and increased arterial CO2 levels –> ventilation-perfusion mismatch
How long do we fast cattle before anesthesia?
24-48 hours food
12-24 hours water
Why do we fast cattle?
Regurgitation and aspiration risk of rumen contents
What can bloat in cattle lead to?
Bloat –> increased P on diaphragm –> limits lung expansion –> decreased ventilation –> decreased arterial O2 and increased arterial CO2 –> ventilation-perfusion mismatch
How long do we fast sheep/goats before anesthesia?
12-24 hours food
+/- water
How long do we fast all ruminants < 4 weeks old and why?
2-4 hours;
Are still nuring, monogastric, and less prone to regurgitation
