Nausea & Vomiting

Nausea: inclination to vomit. Vomiting: ejection or expulsion of gastric contents through the mouth.

Phases of emesis 1.Nausea: imminent need to vomit → associated with gastric stasis. 2.Retching: labored movement of abdominal & thoracic muscles. 3.Vomiting: forceful expulsion of gastric contents due to GI retroperistalsis.

Vomiting is triggered by afferent impulses to the vomiting center found in medulla. Impulses are received from sensory centers such as: chemoreceptor trigger zone (CTZ), cerebral cortex, and visceral afferents from the pharynx & GIT.

Afferent impulses are integrated by vomiting center resulting in efferent impulses to the salivation center, respiratory center and pharyngeal, GI and abdominal muscles leading to vomiting.

Numerous neurotransmitter receptors are located in: vomiting center, CTZ & GIT. These receptors include: –Cholinergic. –Histaminic. –Dopaminergic. –Opiate. –Serotonin. –Benzodiazepine. Upon stimulation of these receptors → vomiting takes place.

Anticipatory NV → NV associated with the administration of noxious, cytotoxic agents or by the anxiety associated with such treatments. NV occur frequently after operative procedures. NV in ♀ 3 times > ♂. Hyperemesis gravidarum → NV during pregnancy.