Nausea and vomiting

Physiopathology

The two centers in the reticular zone of the bulb are the chemoreceptor zone and the integrated center. The afferent pathways come from almost every site on the body. The vagal ducts are of enormous importance, but vagotomy does not cancel out vomiting. The afferent and sympathetic pathways do not mediate the vomiting that occurs with abdominal distention. Vomiting arises when both somatic and visceral efferent pathways cause glottis closure, diaphragm contraction, pylorus closure, and gastric relaxation followed by antipersital contractions that run from the middle of the stomach to the incisura and end in abdominal, diaphragmatic, and intercostal contractions. Vomiting is accompanied by signs and symptoms of discharge from the autonomic nervous system.

Causes

They are observed related to all disorders of the digestive tract and especially obstructions, because obstruction at a high point causes early vomiting. Alterations of the autonomic system, such as drug use, psychogenic problems and ingestion of harmful substances, are other frequent causes. Factors that decrease blood flow and oxygen delivery to the bulb (such as vascular occlusive shock and increased intracranial pressure) can induce emesis. Emetics produce their effects by direct stimulation of the central nervous system or irritation of the gastric mucosa. Metabolic abnormalities such as acidosis, uremia, and hyperkalemia affect the center of emesis.

Patterns

Sudden and often projectile vomiting, without prior nausea, strongly suggests a central cause. Hypertrophic pyloric stenosis also causes projectile emesis. Fecaloid vomiting suggests small bowel obstruction or gastrocolic fistula. Vomiting immediately following meals is seen in uremia, gastritis, upper intestinal obstruction and in stomach neoplasms.

Consequences of vomiting

Metabolic, chronic vomiting shows hypovolemia, hypokalemia and metabolic alkalosis, and total depletion of body sodium. Potassium is excreted by the kidney instead of sodium because hydrogen ions are not available for exchange. Further volumetric contraction can cause paradoxical aciduria in an attempt to conserve sodium. Other causes: Forced, repeated arching can cause Mallory-Weiss tear or rupture of the distal esophagus (Boerhaave syndrome).