ASA Drug Selection Flashcards
What ASA statuses are considered low and high risk?
LOW:
I - healthy patient without disease
II - mild systemic disease that is managed
HIGH:
III - moderate systemic disease (one organ system)
IV - serious systemic disease, patient is very compromised (more than one organ system)
V - moribund, comatose, not expected to survive
How does the use of premedication differ in higher risk patients?
more reliance on premeds —> less induction with multimodal agents and limited inhalants
more reliance on anxiolytics, anti-inflammatories, and locoregional blocks
What are the 3 components of all premeds? What are 2 optional additions?
- opioid
- sedative or stress reliever
- anti-inflammatory
- anticholinergic
- gastroprotectant and motility
What are doses of drugs like in high risk patients?
adjusted —> never use textbook dose
plan on titration unless patient is stressed, anxious, or aggressive
What are 7 aspects of low risk protocol for anesthesia?
- +/- objective testing
- little if any stabilization
- almost any drugs*
- wider range of doses
- standard periop care
- little troubleshooting
- postop care routine
What are 6 aspects of high risk protocol for anesthesia?
- objective testing based on risk class
- optimization pre-surgery
- specific drugs with narrow ranges*
- periop care individualize
- define and prepare for problems
- intensive postop care
What are 4 aspects of low risk protocol premeds?
- Acepromazine
- Dexmedetomidine mini dose (3-10 mcg/kg)
- all opioids
- most NSAIDs
What are 5 aspects of high risk protocol premeds?
- Midazolam
- Dexmedetomidine micro dose (1-2 mcg/kg)
- certain opioids
- other anti-inflammatories: steroids, local anesthetics, Robenacoxib)
- GI protective and motility
When is critical case anesthesia necessary? What 2 premeds are most commonly used?
ASA IV
- benzodiazepines - Midazolam, Diazepam
- opioids - Fentanyl
(very safe)
What is a common critical case protocol?
- PREMED: Fentanyl (5-10 mcg/kg), Midazolam (0.2 mg/kg)
- INDUCTION: propofol
- inhalant
- CRI
- +/- local bloackade
What opioid analgesic works best in canine and feline patients? What are other options?
Fentanyl
- oxy/hydormorphone
- morphine
- merperidine
- buprenorphine
- butorphanol
What opioid sedation works best in canine and feline patients? What are other options?
Butorphanol
- oxy/hydromorphone
- morphine
- meperidine
- fentanyl
- buprenorphine
Why is fentanyl considered a disappointing low risk premed? How does it affect potency other aspects of anesthesia?
though potent, it is short-acting, which doesn’t make sense when surgical pain is long-lasting
excellent attachment at mu receptor allows uncapped effect from other receptors, cause an autonomic overdrive effect which makes it more difficult to receive the induction agent
Since fentanyl is short-acting, why isn’t a CRI of fentanyl not commonly followed up after surgery?
CRI is unable to subdue sympathetic responses to surgical pain and can create a pro-inflammatory state —> upregulated stress response = cannot maintain steady levels of anesthesia or analgesia
What are 2 reasons that high risk drugs not work well with low risk cases?
- roller coaster anesthesia - drugs will not practically sedate mostly healthy patients and unsedated patients will require more isoflurane
- healthy circulation and oxygen delivery alters pharmacokinetics to titrable drugs - may not last as long or have any effect and can cause arousal, perception of pain, and hyperalgesia
What premedication sedatives are recommended for low-risk and high-risk patients?
LOW-RISK = Acepromazine, mini dose alpha-agonists (xylazine, dex, med)
HIGH-RISK = Benzodiazepines (Diazepam, Midazolam), micro dose alpha-agonists, Butorphanol
What is the major pro in the used of Acepromazine as a premedication sedative? 4 cons? In what patients is it used?
major tranquilizer allows for MAC reduction
- alpha-antagonism causes hypotension (vasodilation) and hypothermia
- durations of action can be long (4-12 hr)
- may affect platelet function
- not reversible
LOW RISK, non-aggressive animals
What is the difference between diazepam and midazolam?
DIAZEPAM = propylene glycol carrier, miscibility issues, longer duration of effect, NOT given IM or SQ, irritating IM/IV
MIDAZOLAM = water-soluble, can be given via all routes, not irritating, more potent in certain species
What 4 effects does the propylene carrier of diazepam have?
- cardiac depressant
- viscosity changes
- hemoglobin changes
- hepatic metabolism
What are 4 pros to using Benzodiazepines (Diazepam, Midazolam)? 2 cons? In what patients are they used?
- minimal cardiovascular and respiratory depression
- reversible - Flumazenil
- amnestic
- mild tranquilizer
- capable of cause excitement
HIGH RISK —> tranquilization higher
What are 3 pros and cons to using alpha agonists as premedication sedatives?
- reliable and consistent analgesia, anxiolysis, and muscle relaxation
- reversible
- creates vascular tone helpful for blood pressure maintenance and reduces hemorrhage
- smallest does = greater effect
- causes bradycardia and reduced CO
- increased vascular tone can make monitoring challenging
How does Dexmedetomidine cause bradycardia?
peripheral vasoconstriction increases vascular tone and reflexive bradycardia
What causes the varied side effects of the different alpha agonists?
alpha-1 receptor ratios —> postsynaptically!
- xylazine - 160:1
- dex, med - 1620:1
What are the 3 ranges of doses for alpha agonists? What effects result from each?
0.2-2 mcg/kg = micro dose, normotension, 3-10 mins
3-10 mcg/kg = mini dose, normotension to mild increased BP, 30-40 mins
10-40 mcg/kg = “label” dose, moderate increase in BP to hypertension, 1-2 hr
How are the alpha agonists used in different risk patients?
- xylazine = not used in small animals
- dex/med = micro dose for high risk, mini dose for low risk
What are 4 beneficial effects of butorphanol (Torb)?
- anti-tussive - intubation!
- anti-nausea - general anesthesia, especiallly when pure mu opioids are used
- provides increased threshold to stimuli
- benign cardiorespiratory effects
What are 2 pros to using opioids in premedication? What type is most commonly used?
- first line of treatment and pretreatment for acute and/or severe pain
- regardless of risk status, they provide safe analgesia
pure mu agonists
What are 6 cons to using opioids in premedication?
- don’t usually sedate, can cause excitement
- nausea and vomiting
- urinary retention
- contributes to inflammation and hyperalgesia
- histamine release
- biliary duct spasm
What opioid is not known to cause excitement? Which one causes histamine release?
butorphanol
morphine
What opioids are able to be used in low and high risk patients? Which is specifically only used in low risk patients?
- Butorphanol
- Buprenorphine
- Hydro/Oxymorphone
- Morphine
- Fentanyl
transdermal or topical Fentanyl
What 4 opioids are good for high-risk cases?
- Methadone
- Oxymorphone
- Remifentanil
- Fentanyl
What are 4 pros to using anticholinergics in premedication?
- reduces secretion moisture
- bronchodilating
- increases heart rate
- decreases vagal influences
What are 6 cons to using anticholinergics in premedication? What animals are most sensitive to side effects?
- increased myocardial work*
- decreased arrhythmogenic threshold*
- increases secretion viscosity
- negative pulmonary pressure
- may cross BBB and stimulate CNS
- ileus
cat
What are the 2 most common anticholinergics used in premedications? When are they used?
- Atropine - emergency resuscitation
- glycopyrrolate - reduced BP and HR, pediatrics/neonatal, ocular/cardio/neuro patients
ONLY WHEN NEEDED
What are 2 pros and 4 cons of using anti-inflammatories in premedications?
- reduce a different form of pain
- counteract opioid hyperalgesia and pro-inflammation
NSAIDs cause:
- reduced renal perfusion during hypotension
- reduced platelet adhesion
- bronchoconstriction
- reduced gastric cell turnover
In what patients are NSAIDs used?
low risk
- Rimadyl
- Metacam
- Deramaxx
- Onsior
- Previcox
What are some anti-inflammatory options for high-risk patients?
- prednisone
- lidocaine
- dexamethasone
- Zeel
- diclofenac
- cryotherapy
- laser therapy
What are 4 pros to using ketamine/telazol as induction agents?
- cardiosupportive
- analgesic at low doses (NMDA antagonist)
- bronchodilator
- IM or IV administration
What are 5 cons to using ketamine/telazol as induction agents?
- sympathomimetic
- increases ICP and IOP at high doses
- increases cardiac output
- hyperalgesic at high doses
- administration is painful (pH = 4)
What are 4 pros to using propofol as an induction agent?
- ultrashort acting
- metabolized very quickly, non-cumulative = repeated boluses and CRI
- extrahepatic clearance
- antiemetic
What are 5 cons to using propofol as an induction agent?
- significant CV depression by loss of baroreflex, hypotension, and bradycardia
- apnea and hypoxia
- myclonic twitching
- Heinz body anemia in cats
- soybean and lecithin carrier requires single use
What are 2 pros and 5 cons to using etomidate as an induction agent?
- ultrashort acting
- minimal cardiovascular and respiratory effects
- increases EEG activity
- myoclonus
- propylene glycol carrier = painful on injection, hemolysis
- expensive
- adrenocortical suppression
What are 5 pros to using alfaxalone as an induction agent?
- cardiovascular and respiratory support
- administered IV or IM
- short-acting
- no Heinz body anemia issues in cats
- non-cumulative = repeated boluses, CRI
What are 2 cons to using alfaxalone as an induction agent?
- expensive
- requires solid premed
What is important to note about all induction agents? How can safety be assured?
have serious consequences (CNS depression) with equally deleterious effects in low and high risk patients
- total dose is minimized with solid premeds
- titrated
- optimize patients
- Alfaxalone or Etomidate in high-risk patients
What are the 3 most common induction agent options in low-risk patients?
- Ketamine (+ benzo)
- Propofol
- Alfaxalone (IM)
What are the 5 most common induction agent options in high-risk patients?
- Alfaxalone (IM or IV)
- Fentanyl, Diazepam/Midazolam, Propofol
- Fentanyl, Diazepam/Midazolam, Ketamine
- Ketamine, Propofol
- Etomidate
What are 2 pros and 4 cons to using isoflurane as an inhalant?
familiarity and predictability
- vasodilation
- anesthesia morbidity and mortality
- postop cognitive dysfunction
- postop nausea and vomiting
What are 2 pros and 3 cons to using sevoflurane as an inhalant?
speed of induction/recovery and improved postop function
- speed of induction/recovery
- need for adequate premed
- cost
In what patients are isoflurane and sevoflurane recommended?
LOW RISK = Isoflurane
HIGH RISK = Sevoflurane
Sevoflurane offers quality anesthesia. How can isoflurane be comparatively used?
if it is minimized by….
- solid premedication
- patient optimization
- titration of induction agent
- local blockade
- anti-inflammatory drugs and techniques
ASA risk and drug usage:
What is a reason fentanyl is a poor premed for healthy or low risk cases?
a. It Improves “steady” levels of anesthesia
b. It decreases sympathetic tone
c. It upregulates stress response via its potent effect at opioid receptors
d. It decreases inflammatory response
C
True or false: Because of their benign cardiovascular effects, Benzodiazepines should be used for low risk (ASA I, II) patients.
FALSE —> used in high-risk patients
True or false: Non-steroidal anti-inflammatories should only be utilized in low risk
TRUE
True or false: Flumazenil is a reversal agent for Benzodiazepines
TRUE
There is no specific induction agent for high or low risk cases, but alfaxalone appears to offer more safety than other agents because
a. It reduces inflammation
b. It relieves pain
c. It is considered cardio and respiratory supportive if administered after a solid premedication
d. It reduces stress
C
True or false: The higher the ASA risk class, the less relative inhalant dose should be used
TRUE
What is a common issue surrounding the use of diazepam in veterinary patients?
a. It is Not miscible with ketamine
b. It has a very acidic pH
c. It is a potent Cardiac stimulant
d. It causes Tissue irritation when given IM due to its carrier, propylene glycol
D
Premedications will always have:
a. Anticholinergic
b. Opioid
c. Gastroprotectant
d. Anti-inflammatory medication
B
Why is fentanyl used as a premed in human patients more often than in veterinary patients?
a. Veterinary patients have less fear surrounding surgical procedures
b. Fentanyl has a higher distribution volume in apes compared to human patients
c. Human patients can communicate fear and stress to us more effectively than veterinary patients; and likewise we can calm that stress with our interactions more effectively than we can with veterinary patients
d. There is less reliance on local blocks in human patients
C
Induction safety in high risk patients is increased when:
a. Etomidate is not used
b. Induction agents are titrated
c. Propofol or Ketamine/valium is utilized
d. Total induction dose is increased
B
Ketamine as an induction agent causes which of the following? (and because of this is considered blood pressure supportive in low doses)
a. Endogenous opioid release
b. Nicotinic activity
c. Adrenocortical axis suppression
d. Increased sympathetic tone
D
True or false: Alpha agonist drugs cause all of the following: vasoconstriction, decreased vascular tone, and reflexive bradycardia
FALSE —> increased vascular tone
True or false: Because of its potent alpha blocking effects and long duration of effect in veterinary patients, acepromazine is an example of a drug that should be used for Low Risk cases (ASA I and II) cases.
True
You are inducing a high risk case with propofol. To minimize its impact on the cardiovascular system, you can mix it with which of the following other induction agents?
a. Etomidate
b. Ketamine
c. Dexmedetomidine
d. Thiopental
B
True or false: Xylazine is an alpha two agent commonly used in small animal patients because its cardiovascular effects are less profound than that of dexmedetomidine.
FALSE —> not used in small animals
True or false: Opioids should be used in all premed protocols despite the risk status
TRUE —> extremely safe
What alpha agonist dose would be considered appropriate for higher risk patients?
a. 5 mcg/kg dexmeditomidine
b. 0.2 mcg/kg dexmeditomidine
c. 40 mcg/kg dexmeditomidine
d. 10 mcg/kg dexemeditomidine
B
What is the most important aspect of the anesthesia menu because it provides a majority of the analgesia, sedation, anxiolysis for surgical procedures?
a. Recovery
b. Maintenance or gas anesthesia
c. Induction
d. Premedication
D
True or false: Because of their lengthy clinical effect (days) in canine species, fentanyl patches and transdermal fentanyl (recuyra) should only be used as premed or postmeds in low risk cases.
TRUE
Anticholinergics should be considered a part of the premedication in all of the following scenarios except?
a. An ovh surgery in a mid aged pomeranian
b. A corneal conjunctival flap surgery in an aged DSH
c. A pediatric or neonatal patient spay
d. A 10 year old Labrador with a chronic foreign body and resting heart rate of 50
A
True or false: Anti-inflammatories can only be utilized in low risk patients
FALSE —> NSAIDs are for low-risk only, but there are other anti-inflammatory options, like cryo/laser therapy, prednisone, lidocaine, dexamethasone, etc.
True or false: High-risk drugs do not work well in low-risk cases.
TRUE
