15 nausea and vomitting Flashcards
what is vomiting/emesis
defined as the forceful expulsion of gastric contents
what controls vomiting
the vomiting centre
what is vomiting a response to
a physiological response to remove toxic substances
what happens before vomiting
nausea
what are physiological causes of vomitting
- ingestion of toxic substances
- vestibular system (motion sickness)
- cranial nerve - irritation of pharynx
- vagan and ENS - irritation of GIT
where is the vomiting centre located
in the medulla
what does the vomiting centre receive input from
postrema/chemoreceptor trigger zone
input from other brain zones depending on the stimulus (pain, fear, movement etc)
what are the regions of the brain not protected by the BBB
- subfornical organ
- OVLT
- posterior pituitary
- median eminence
- area postrema
- pineal gland
what does the subfornical organ control
circulating levels of Ang II
what does the pineal gland control
circadian rhythm
what does the OVLT control
temperature and fever
what does the posterior pituitary control
oxytocin and vasopressin levels
what does the median eminence control
neurohormonal control of ANS
what does the area postrema control
circulating toxins and vomiting reflex
phases of emesis
signals from vomiting centre causes:
- abdominal pressure
- respiration to stop
- LES relaxation
- closure of glottis
the stomach squeezes and diaphragm and abdominal muscles contract
cascade of vomit
what do emetics do
cause vomiting
when would emetics be used
only in emergency situations after ingestion of toxin
no OTC emetics available
which receptor system regions underly emesis
- CTZ
- vomiting center
- vestibular nuclei
- visceral afferents
which receptors underly emesis
- D2
- 5-HT3
- mAch
- H1
what can targeting receptors involved in emesis do
reduce emesis
what should be used for travel sickness
- cinnarizine (H1 antihistamine)
- promethazine (H1 antihistamine, weak mAch antagonist)
other common antiemetics
- hyoscine (mAch antagonist)
- ondansetron (5-HT3 antagonist)
what is ondansetron used for
to reduce nausea and vomiting during cancer treatment, post op N&V etc
what is hyperemises gravidium
excessive nausea and vomiting during pregancy, no clear cause for it
how is hyperemesis gravidum treated
- antiemetics, vitamins, steroids, IV fluids
