Vomiting occurs when the vomiting centre in the medulla receives stimulation from one or more pathways. These pathways explain why vomiting can occur with gastrointestinal disease, neurologic disease, medications, pregnancy, motion sickness, metabolic disorders, or infection. Trigger Pathway Mechanism Examples Gastrointestinal irritation Stretch, inflammation, infection, or obstruction stimulates visceral afferent nerves Gastroenteritis, bowel obstruction, appendicitis, pancreatitis Chemoreceptor trigger zone Blood-borne toxins, medications, and metabolic abnormalities stimulate central receptors Opioids, chemotherapy, uremia, DKA, sepsis Vestibular system Inner-ear stimulation activates nausea/vomiting pathways Motion sickness, vertigo, Ménière disease Higher cortical centres Pain, anxiety, smell, fear, or emotional triggers stimulate nausea pathways Severe pain, anxiety, unpleasant odours Increased intracranial pressure Pressure on CNS vomiting pathways can cause vomiting, sometimes without nausea Head trauma, tumour, hemorrhage, meningitis During repeated vomiting, the patient loses gastric fluid rich in water, hydrogen ions, chloride, potassium, and sodium. Loss of hydrogen and chloride can contribute to metabolic alkalosis. Loss of potassium can contribute to weakness, dysrhythmias, ileus, and worsening nausea. Fluid loss can decrease circulating volume, causing tachycardia, orthostatic hypotension, reduced urine output, acute kidney injury, and shock. For...