Pathophysiology

Involuntary forceful ejection of stomach matter through the mouth

Mechanism - Relaxation of LOS, valsalva menouvre, expulsion

Medullary vomitting centres causing comitting:

• Chemoreceptors - detecting noxious stimuli e.g. uraemia, DKA
• Visceral afferents from GIT e.g. stomach distension
• Visceral afferents from outside the GIT e.g. Biliary colic, ACS
• Afferents from extramedullary centres in brain e.g. olfactory, vestibular centres

Other mechanisms:

• Motion sickness - CNVIII stimulating vomiting centres
• Chemo/surgery - Increased 5HT levels activate chemoreceptors

Causes

Acute (<3 days):

• mechanical obstructions of the GIT - bowel obstruction, obstruction of the biliary tree
• GIT infections, food poisoning
• CNS infections
• stroke
• motion sickness
• hypercalcaemia