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