Flashcards in Premedication Deck (29)
what are goals of premedication?
-reduce anxiety, amnesia
-reduce risk of aspiration
-nausea and vomiting prophylaxis
-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?
-minimal effects on ventilation and cardiovascular
-raise seizure threshold
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
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
-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)
-no amnestic effect
-sphincter of Oddi spasm
-dysphoria in patients without pain
-well absorbed IM
-may cause orthostatic hypotension, pruritus, respiratory depression
-dose 0.1-0.2 mg/kg IM (15-30 min)
-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
-given to reduce the amount of opioids required postop
-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
-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)
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)
-serotonin receptor antagonists (Zofran)
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?
dose: 150-300 mg PO; 50 mg IV
onset: 60-90 min
duration: up to 9 hrs
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?
-Parkinson's disease (dopamine blockage)
*push slow (potential for extrapyramidal effects; often r/t tardive dyskinesia
raises the gastric pH of fluid already present in the stomach by neutralizing the hydrogen ions with a base
*disadvantage: increases volume
*use a nonparticulate (non colored, no Mylanta) like sodium citrate (Bicitra)
*seen often in L&D; always prepare as if you may intubate
what is the dose of sodium citrate?
15-30 ml PO (15-30 min)
describe proton pump inhibitors
-most effective in controlling gastric acidity and volume
-limits the last step in secretion of hydrogen ions: hydrogen-potassium ATPase
*clinical use in moderate to severe GERD
*takes daily admin over 5 days to inhibit secretion 66%
*better than H2 blockers in inhibiting secretion, healing duodenal and gastric ulcers, and treating reflux esophagitis
what is the dose of omeprazole (Prilosec)?
20mg PO (single dose takes > 3 hrs to increase pH)