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Nausea and vomiting — causes and complications

By Alan Worsley, MRPharmS, PhD, and Andrew Husband, MRPharmS, MSc

Nausea and vomiting are biological defence mechanisms, associated with a variety of stimuli and conditions. This article explains some of the common causes of nausea and vomiting and the complications that can arise

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Alan Worsley and Andrew Husband are senior lecturers in pharmacy practice at the University of Sunderland

David Mack/SPL

Vomiting reflex

Computer artwork of the vomiting reflex

SUMMARY

Nausea is the word used to describe the sensation of discomfort and unease in the stomach and is derived from the Greek word for sea-sickness (naus means ship). Nausea itself is not an illness but a symptom associated with a variety of conditions. Nausea and vomiting are produced by the same stimuli and can be viewed as a progressive response to increased stimulus.

The act of vomiting (emesis) is caused by a series of changes within the gastrointestinal tract, in co-ordination with respiratory movements. Generally, salivation precedes the ejection of vomitus and there is a simultaneous increased volume of inspiration into the lungs, which increases abdominal pressure. The epiglottis closes and the soft palate of the mouth rises to prevent vomitus entering the lungs. The pyloric region of the stomach undergoes a strong contraction, while the fundus, cardiac sphincter and oesophagus remain relaxed and the external muscles of the anus and urethra contract. As a result, the stomach expels the vomitus with great force into the mouth and out of the body.

This sequence may be repeated in co-ordination with respiratory cycles, and retrograde peristalsis from the small intestine to the stomach may refill the stomach several times. Retching is a similar process to vomiting, where the movements involved are less severe and do not result in ejection of vomitus.

Complications If vomiting is left untreated, in addition to causing distress, hypokalaemic hypo-chloraemic alkalosis (volume depletion, loss of gastric hydrogen ions and alterations in the renin-angiotensin-aldosterone system) can result.

Vomiting can also cause mucosal damage such as Mallory-Weiss tears, or rupture the oesophagus (eg, Boerhaave syndrome). A fall in haemocrit and subsequent endoscopy should identify any bleed and associated physical damage. Gastrointestinal rupture as a result of vomiting is particularly dangerous in alcoholics who have developed oesophageal varices.

Another complication associated with uncontrolled vomiting is the possible aspiration of the stomach contents into the lung, potentially leading to aspiration pneumonitis and pneumonia.

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