Premedication Flashcards
(29 cards)
what are goals of premedication?
- reduce anxiety, amnesia
- pain relief
- sedation
- reduce risk of aspiration
- nausea and vomiting prophylaxis
- antisialagogue
- reduce MAC
- prophylaxis of allergic reaction
what is the MOA of benzodiazepines?
- sedation produced by intensification of GABA effects
- anxiolysis produced by glycine-mediated inhibitory effect on neuronal pathways in the brain
what are the advantages of benzos?
- sedation
- anxiolysis
- amnesia
- minimal effects on ventilation and cardiovascular
- raise seizure threshold
- reduce MAC
what are disadvantages of benzos?
- no analgesia (must consider whether pain med is needed more in preop)
- possible paradoxical reaction (confusion, agitation)
- implicated as teratogenic during first trimester (cleft lip)
what is the MOA of droperidol (Inapsine)?
antagonizes the activation of dopamine receptors, interferes with transmission mediated by serotonin, NE, GABA; also alpha-adrenergic blocker
what are effects of droperidol?
- outward appearance of calm
- dysphoria, restlessness, fear of death
- antiemetic effects
what is the MOA of opioids?
bind to specific receptors throughout the central nervous system, tissues
what are the advantages of opioids?
- no direct myocardial depression
- pre-emptive analgesia
- analgesia in pre-existing pain, painful procedures
- decreases incidence of increased HR during surgical procedure
what are disadvantages of opioids?
- depresses ventilation, particularly RR; apneic threshold elevated; hypoxic drive decreased (not good w/ sleep apnea)
- orthostatic hypotension
- N/V
- no amnestic effect
- sphincter of Oddi spasm
- dysphoria in patients without pain
- histamine release
describe morphine
- well absorbed IM
- histamine release
- may cause orthostatic hypotension, pruritus, respiratory depression
- dose 0.1-0.2 mg/kg IM (15-30 min)
describe fentanyl
- about 100x more potent than morphine
- usually given just prior to induction
- 5-8 mcg/kg blunts response to laryngoscopy
- most commonly used opioid in anesthesia
- dose IV 1-2 mcg/kg (30-60 sec) last about 30 min to an hour
describe NSAIDS
- given to reduce the amount of opioids required postop
- pre-emptive analgesia
- beware: prostaglandin inhibition may decrease platelet aggregation
- caution: elderly, h/o gastric ulcers, renal impairment
- decision to give must involve surgeon
- acetaminophen contraindicated w/ hepatic impairment
describe antihistamines
- H1 antagonist given to pts. with h/o chronic atopy or at risk for allergic reaction
- give along with a H2 antagonist
- Benadryl dose: 0.5-1 mg/kg PO
describe alpha 2 agonist clonidine
- centrally acting alpha 2 agonist which blunts the autonomic nervous system reflex responses to surgical stimulation (such as increased HR and BP)
- can decrease anesthetic requirement, decrease MAC
- potential for bradycardia and hypotension- give fluids
dose: 5 mcg/kg PO (90 min)
describe anticholinergics
- historical use
advantages: vagolytic effect, antisialogue effect (turning prone), sedation and amnesia (atropine/scopolamine cross BBB)
disadvantages: central anticholinergic syndrome, mydriasis and cycloplegia (caution w/ glaucoma), tachycardia and arrhythmias (don’t give to CAD pts.)
which anticholinergics are best for increase in HR, antisialogue effects, and sedation?
- atropine increase in HR (give to infants 6 months or <)
- scopolamine best for sedation
- glycopyrrolate best antisialogue effect
what are the different types of antiemetics
- GI prokinetics (metoclopramide)
- butyrophenones (droperidol)
- phenothiazines (promethazine)
- serotonin receptor antagonists (Zofran)
- corticosteroids
what are the goals to prevent aspiration?
- gastric pH > 2.5
- gastric volume < 25 ml
how do H2 antagonist provide prophylaxis against aspiration?
- increase the pH of whatever is released in the stomach from the time medicine takes effect
- takes time to change pH of contents already in stomach since that must be diluted over time
- *does not change volume
- *need to receive the night before and morning of
what are different histamine2 receptor antagonists?
- ranitidine (Zantac)
dose: 150-300 mg PO; 50 mg IV
onset: 60-90 min
duration: up to 9 hrs - famotidine (Pepcid)
dose: 20-40 mg PO; 20 mg IV
onset: 60-90 min
duration: 10-12 hrs
how does gastrokinetic agents (metoclopramide) provide prophylaxis against aspiration?
enhances the effects of ACh on the intestinal smooth muscle to :
1) speed gastric emptying
2) increase lower esophageal sphincter tone
3) relax the pylorus and duodenum
4) lower gastric volume
* does not effect gastric pH
what is the antiemetic effect of metoclopramide?
dopamine antagonist in the CTZ of the CNS
what is the dose and onset of metoclopramide?
PO 10-15 mg (30-60 min)
IV 10 mg (15-30 min)
peds: 0.25 mg/kg
what are contraindications of metoclopramide use?
- intestinal obstructions
- Parkinson’s disease (dopamine blockage)
- push slow (potential for extrapyramidal effects; often r/t tardive dyskinesia
