B5-067 Nausea and Vomiting Flashcards
- located in medulla
- direct contact with blood through leaky capillaries
chemoreceptor trigger zone (CTZ)
what drugs are the most effective in treating nausea/vomiting?
serotonin (5-HT3) antagonists
-setron
what drug class is more effective for nausea/vomiting associated with chemotherapy?
NK-1 antagonists
-pitants
cytotoxic agents stimulated CTZ which releases […] to stimulate the receptors on the vomiting center
ACh
the vestibular nuclei contain what type of receptors?
2
H1 and M3
what drug class is most effective in treating motion sickness?
H1- antagonists
side effects include dry mouth, decreased saliva, blurry vision, and drowsiness
muscarinic antagonists
Hyoscine
- inhibits 5-HT3 receptors
- works at the level of stomach and CTZ
ondansetron
used for pre-surgical nausea prophylaxis
hyoscine
muscarinic antagonist
urge to vomit
nausea
vomiting leads to an electrolyte imbalance causing
metabolic alkalosis
most common causes of vomiting in adults
3
- food poisoning
- migraines
- chemotherapy
most common causes of vomiting in infants
5
- food allergies
- viral gastroenteritis
- milk intolerance
- infections
- blockage of GI tract
mostly localized to GI
GI causes of nausea and vomiting
3 general groups
- mechanical/obstruction
- motility/functional (ileus)
- infectious/inflammatory (-itis)
non GI causes of nausea and vomiting
4 general categories
- CNS
- endocrine/metabolic
- toxic/medication
- other (stress, pain, anxiety, etc)
what is causing in the following disorders leading to N/V?
- hyperthyroidism
- hyperparathyroidism
- adrenal insufficiency
- diabetes
- pregnancy
- hyperthyroidism: increased T3, T4
- hyperparathyroidism: increased PTH, Ca++
- adrenal insufficiency: decreased cortisol
- diabetes: increased glucose
- pregnancy: increased hCG, P4, E2
nausea/vomiting with a duration of 1 week or less is
acute
more than 1 week is chronic
nausea onset 1-8 hours after meal indicates
4
- food poisoining
- gastritis
- ulcer
- bulimia
how does the “gag reflex” trigger vomiting?
pharyngeal stimulation -> NTS -> vomiting reflex
how do drugs/hormones activate the vomit reflex?
activate gastric mucosa and/or CTZ
-> NTS -> brainstem vomiting center
how does motion vertigo induce vomiting?
labyrinth -> cerebellum -> brainstem vomiting center
how does overeating cause vomiting?
- activation of stretch receptors triggers vagus to release ACh -> ACh stimulates vomiting center
- increased pressure on cardiac spinchter -> opens to allow vomit out
how does anxiety/stress induce vomiting?
adrenal gland releases catecholamines -> decreased digestive system activity -> gastroparesis
- “pacemaker” cells of stomach
- generate slow waves causing phasic contractions
interstitial cells of Cajal
[…] is a major cause of gastroparesis due to nerve damage
diabetes
what test can be used to assess gastroparesis?
gastric empyting study (nuclear scanning test)
how does motion sickness cause vomiting?
unfamiliar, unnatural motion stimuli -> vestibular labyrinth -> vestibular nuclei -> cerebullum -> ACh, H1 -> vomiting center
H1 antagonists that cause significant drowsiness
2
dimenhydrinate
diphenhydramine