Premedication Agents Flashcards
What 7 things should be provided in an anesthesia experience?
- critical body system support and protection (depressed function of the respiratory, circulatory, and nervous systems)
- sedation
- muscle relaxation
- anxiety reduction
- pain relief
- amnesia
- novel means to facilitate intervention or surgical approach
What are the 3 goals of anesthesia protocols?
- reduces pain, stress/anxiety, and inflammation (PSI)
- provide reversible CNS depression, no movement, musculoskeletal relaxation, and amnesia
- offer a controlled shock state with oxygen/glucose delivery and waste disposal
What part of the anesthesia protocol is the most important? Why?
premedication
allows for a majority of analgesia, relaxation, and anxiolysis
Is premedication only sufficient to provide good anesthesia?
NO
What 5 things are high inhalant concentrations linked to?
- post-op nausea and vomiting
- post-op congnitive dysfunction
- poor wound healing
- organ dysfunction (CNS and cardiorespiratory depression!)
- musculoskeletal disability
What does inhalant anesthetics not provide?
lasting pain, stress, or inflammatory relief
What are the 6 premedication goals? What is a possible additional goal?
- sedation
- anxiety reduction or loss
- muscle relaxation
- pain relief
- GI motility and protection
- decreased inflammation
amnesia
What are the most common GI agents, analgesics, and anti-anxiety/sedatives used in premedications?
antiemetics, motility agents, gastric protectants
opioids, alpha agents
benzodiazepines, phenothiazines
What are 6 common antiemetics and GI motility modifying agents used in premedications? What are some examples of each?
- antihistamines: Diphenylhydramine, Acepromazine
- dopamine antagonists: Metclopramide, Acepromazine
- serotonin antagonists: Ondansetron, Dolasetron
- antimuscarinics: Scopolamine, Glycopyrolate
- neurokinin antagonists: Maropitant (Cerenia)
- phenothiazines: Acepromazine, Chlorpromazine
How does the use of Maropitant (Cerenia) affect inhalant anesthesia?
decreases the anesthetic requirements
- decreases MAC by 15%
What are 3 reasons for adding butorphanol to other opioids for premedications?
- great sedative
- antiemetic
- antitussive
What aspect of the GI system is important to minimize perianesthetically?
acid and its deleterious effects
What 5 drug classes are used as esophageal and duodenal protectants in premedications? What are examples of each?
- antacids - calcium carbonate (neutralizes acid)
- mucosal protectant - Sucralfate
- H2 antagonists - Famotidine
- prostaglandin analog - Misoprostal
- PPI - Omeprazole (blocks H/K ATPase)
When are oral antacids especially useful?
- upper GI surgery
- thoracic surgery
In what 5 situations is the use of antiemetics especially helpful?
- if opioids are used in premeds
- obese patients
- patients with pre-existing GI disease or laryngeal/pharyngeal disease
- upper GI/abdominal surgery
- brachycephalics
How do the outcomes with PRN vs preemptive narcotic use in surgery compare?
PRN = IV bolus when pain recognized = increased beta-endorphin (stress hormones), increased lactate, sepsis, DIC, 27% mortality rate
PREEMPTIVE = CRI fentanyl = reduced beta-endorphin, <1% mortality rate
What novel long-acting opioid option has been developed? What allows it to reach the optical environment?
transdermal fentanyl solution with one-time application for moderate surgical pain (3-4 day repository effect)
octyl salicylate and isopropanol = crosses the stratum cornea
What opioids provide the most pain relief? Which one is most common in veterinary medicine?
- fentanyl
- oxymorphone
- hydromorphone**
- morphine
- buprenorphine
- butorphanol
How is the type of opioid chosen?
pure Mu agonists are used when pain is significant
- hydro/oxymorphone vs torb
What opioid works fantastically in cats?
buprenorphine
When are long-acting opioids commonly used? Examples?
in premedications
- fentanyl
- sufentanil
- alfentanil
- remifentanil
What opioids are not typically coupled with antiemetics? What 3 things do opioids not provide?
oxymorphone and methadone
- inflammatory relief
- stress relief
- keep animals asleep —> narcotization, nausea requires the repetitive administration of propofol or ket/val boluses
How is opioid use affected by ASA status? What 3 effects does it have on systemic organs?
regardless of ASA class, they are the first line treatment for acute and severe pain
- cardiovascularly soothing
- improves respiratory pattern
- improves post-op hemodynamics
What opioid is not shown to improve respiratory patterns?
potent fentanyls
What are 8 disadvantages to using opioids in premedications?
- immunosuppression
- narcosis
- ileus
- nausea
- inappetence
- urinary retention
- tumor metastasis and angiogenesis
- carbon dioxide non-responsiveness
How are alpha-2 agents used as premedications? Examples? How do they compare to opioids? When is use contraindicated?
great sedatives and analgesics in one drug - Xylazine, Medetomidine, Dexmedetomidine
very potent, resulting in significant reduction in cardiac output
patients in cardiac failure
What are 7 advantages to using alpha-2 agonists?
- analgesic and sedative (unlike opioids)
- excellent muscle relaxant (unlike opioids)
- possibly amnesic
- potentiates opioids
- vasoactive
- reversible (unlike Ace)
- works consistently (unlike midaz)
How are alpha-2 agonists able to potentiate opioids? How are they vasoactive? Why are they great for at risk patients?
work at the same G-protein mechanism = supradditive effect
limits capillary bleeding and increases blood pressure
they are reversible
What are the 3 major disadvantages to using alpha-2 agonists?
- need to be combined with other agents for best effects (opioids and benzos)
- need to be used at micro or mini doses
- extremely potent
What are the 3 major potent effects of alpha-2 agonists?
- reduces cardiac output
- reduced need for induction and inhalant anesthetics
- require hemodynamic physiology primer to understand benefit
What are some common benzodiazepines used as premedications? How do they act?
Midazolam (Versed), Diazepam, Flumazenil
short-acting (like fentanyl)
How do benzodiazepines as solo sedative agents compare in sick/neonates and other classes of patients?
work well
often disorients and excites patients —> do not work well
How do benzodiazepines act when combined with other sedatives?
minimizes the more potent agent, acting as a benign filler
How do the doses of Midazolam alter its affect?
LOW DOSE (0.05-0.1 mg/kg) = anxiolytic, increases appetite, arousal
MID DOSE (0.1-0.2 mg/kg) = sedation in sick patients, arousal in healthy patients
HIGH DOSE (0.3-0.7 mg/kg) = very sedating in sick, excitatory (disinhibitory) in healthy