nausea and vomiting Flashcards
what is nausea
unpleasant urge to vomit
what is vomiting
forceful expulsion of stomach contents through mouth/nose by contraction of abdominal muscles
what is vomiting also known as
emesis
what is vomiting frequently preceded by
profuse salivation
sweating
high HR
nausea
what is retching
repetitive reverse peristalsis of the stomach and oesophagus without vomiting
what is regurgitation
effortless movement of swallowed food/ stomach contents back into the mouth
what is regurgitation NOT associated with
nausea
retching
toxics stimulate what cells in the mucosa
enterochromaffin cells
where is the vomiting centre located
medulla oblongata
what do the visceral efferents effect during vomiting
oesophagus = shortens it
stomach = proximal relaxation
small intestine = giant retrograde contraction
what do the motor neurones effect during vomiting
anterior abdominal muscle = contraction
diaphragm = contraction
what do autonomic/somatic efferents effect during vomiting
heart = increase rate & force salivary glands = increased secretions skin = pallor, cold sweat bladder = sphincter constricts anus = sphincter constricts
describe the pathway of vomiting
toxic materials in gut lumen or systemic toxins stimulate enterochromaffin cells in mucosa
enterochromaffin cells release mediators which depolarise sensory afferent terminals in the mucosa causing an AP in vagal afferents to the brainstem.
where is the chemoreceptor trigger zone (CTZ) located
brainstem
consequences of severe vomiting
dehydration loss of gastric protons and Cl- hypokalaemia mallory-weiss tear aspiration of vomit
where is the nucleus of the solitary tract (NTS) located
brainstem
describe the process of vomiting
Intestinal slow wave activity is suspended, retrograde contractions occur from ileum to stomach. Breathing is suspended as the glottis closed to prevent aspiration. LOS relaxes, diaphragm contracts and abdominal muscles compress the stomach causing ejection of gastric contents through open UOS.
how is chemo-induced vomiting treated
triple therapy:
5HT3-receptor-antagonist = odansetron
corticosteroid = prednisolone
Aprepitant
what causes morning sickness
Human chorionic gonadotropin (HCG) produced by placenta
treatment of morning sickness
changes in diet
use of ginger or pyridoxine (vit B6)
wrist acupuncture
what is hyperemesis gravidarum
extreme morning sickness
what causes hyperemesis gravidarum
fluid and electrolyte disturbances or nutritional deficiency due to intractable vomiting in pregnancy
treatment of hyperemesis gravidarum
1st line = antihistamine
2nd antihistamine + dopamine antagonist
list anti-vomiting drugs (6)
dopamine antagonist prokinetic drugs 5TH3 receptor antagonists H1 histamines anticholingeric adjuvant antiemetics
list adjuvant antiemetics (4)
Nk1 receptor antagonists = aprepitant
corticosteriods
benzodiazepines
cannabinoid
mechanism of action of dopamine antagonists
act centrally by blocking the chemoreceptor trigger zone
mechanism of action of prokinetic drugs
increases gastric peristalsis and increase LOS tone, blocks D2 receptor in CTZ
example of prokinetic drugs
metoclopramide, domperidone
mechanism of action of 5HT3 receptor antagonists
blocks 5TH3 receptors in GI tract and CNS
example of 5HT3 receptor antagonists
“-setron”
ondansetron
mechanism of action of H1 antihistamine
blocks H1 receptor in vestibular nuclei and NTS
example of H1 antihistamine
“-zine”
cyclizine
mechanism of action of anticholinergic
blocks muscarinic receptors in vestibular nuclei, NTs,and vomiting centre
example of anticholinergics
hyosine
