GI medications Flashcards
When is early PONV?
within 6 hours
When is late PONV?
6-24 hours
What is the ASA’s recommendation for PONV?
treat only high risk groups but not routine use; use patient’s risk to guide prophylactic therapy
What are some patient factors that increase risk for PONV?
women, non-smokers, hx motion sickness, previous incidence of PONV
What are some surgical factors that increase risk for PONV?
length of procedure, laparotomies, gyn surgery, lap surgery, ENT, breast, ortho
What are some anesthesia factors that increase risk for PONV?
inhalation agents, N20, Neo, narcs, etomidate
Where is the vomiting center located?
medulla oblongata
What are the 4 areas that trigger the vomiting zone?
CTZ, vestibular apparatus (muscarinic 1 receptor), thalamus/cerebral cortex (CNS), and neurons in GI tract
Describe how the vomiting center is triggered.
NT regulate activity in vomiting center. Once activated, efferent signal sent via cranial nerves to vagal parasympathetic fibers and sympathetic chain
What NTs are associated with PONV?
dopamine, serotonin, acetylcholine, histamine, substance P
What NTs act at CTZ?
dopamine, serotonin
What NTs are intrinsic within vomiting center?
substance P, acetylcholine, and histamine
What NTs are in CNS within vomiting center?
???
What NTs are at the vestibular apparatus within the vomiting center?
acetylcholine, histamine (H1 and M1 receptors)
What NTs act on GI tract within vomiting center?
acetylcholine, histamine, serotonin, substance P, and mechanoreceptors.
What are the drug classes used to treat PONV?
anticholinergics, benzamines, benzodiazepines, butrophenones, cannabinoids, glucocorticoids, 5-HT3 antagonists, NK1 antagonists, phenothiazines
What anti-emetics are anticholinergics?
atropine, hyoscine, scopolamine
What antiemetics are benzamines?
metoclopramide
What antiemetics are benzodiapezines?
midazolam
What antiemetics are butrophenones?
droperidol, haloperidol
What antiemetics are cannabinoids?
dronabinol, nabilone
What antiemetics are glucocorticoids?
dexamethasone
What antiemetics are 5-HT3 antagonists?
dolasetron, granisetron, ondansetron, palonosetron, ramosetron, tropisetron
What antiemetics are NK-1 antagonists?
Aprepitant, Fosprepitant
What antiemetics are phenothiazines?
prochlorperazine, promethazine, chlorpromazine
What is the MOA of Scopolamine?
block transmission of impulses from vestibular apparatus to the medulla. can cross BBB.
What is the dose of scopolamine?
5mcg/hr for 72 hours (best 4 hours before stimulus) transdermal provides sustained effect and avoids anticholinergic side effects. If given IV can cause anticholinergic syndrome
What are the uses for scopolamine?
motion sickness, middle ear surgery, N/V with PCA or epidural morphine
True/False: Narcotics increase the sensitivity of vestibular apparatus to motion.
True
What are the side effects of scopolamine?
possible visual disturbances.
What is the MOA of metoclopramide?
stimulate GI tract via cholinergic mechanism and an anti-dopaminergic effect: contraction of lower esoph sphincter and gastric fundus, increased gastric and SI motility, decreased muscle activity in pylorus and duodenum with stomach contraction
Who should you use caution in with metoclopramide?
parkinsons and RLS in high doses due to antidopamine effects
What is the MOA of midazolam?
thought to decrease the synthesis and release of dopamine within the CTZ. give at END OF CASE
What is the MOA of droperidol?
competitive dopamine antagonist, receptor is D2 and ligands are dopamine and GABA
What is the dose of prophylactic droperidol?
(prophylactic)0.625-1.25mg(rescue)
When should you use caution with droperidol?
parkinsons, RLS, high doses black box warning for prolonged QTc
What is the MOA of dexamethasone?
centrally inhibits prostaglandin synthesis and controls endorphin release
What is the dose of dexamethasone?
4mg