Nausea and vomiting are common complaints seen in a variety of settings. The cause may be associated with something as simple as spinning too fast on an amusement park ride. It could also be the result of a medication or the symptom of something much more serious. Nausea and vomiting may occur independently, but generally they come hand in hand and are thought to be controlled by the same neural pathway which makes it easier to discuss them together. Nausea, of course, means the imminent desire to vomit, a general feeling of queasiness. Vomiting (or emesis) refers to the forceful oral expulsion of gastric, or stomach, contents. Retching denotes the labored rhythmic contraction of the chest and abdominal muscles that usually comes before or accompanies vomiting.(1)

Nausea usually precedes vomiting and is associated with a halt in the work that the stomach would normally be doing at that time related to the digestive processes. The activity of the small intestine is also altered. As if that were not bad enough, nausea can be accompanied by other distressing occurrences with the lower intestines as well. The act of vomiting requires the coordinated efforts of several muscles all at the same time.(2) The stomach itself plays a relatively passive role in vomiting, with the major force being provided by the abdominal muscles. There are two very different medullary centers that are actually responsible for the act of vomiting. Those centers are the chemoreceptor trigger zone, and the vomiting center. The vomiting center is located close to other medullary centers, which regulate respiration, vasomotor, and other functions that may play a role in vomiting. It is the vomiting center that actually controls the act of vomiting. It receives messages from the gastrointestinal tract and other parts of the body.(1) When excited, impulses are integrated by the vomiting center, resulting in messages to the salivation center, respiratory center, and the pharyngeal, GI, and abdominal muscles, leading to vomiting.(3)

The chemoreceptor trigger zone by itself cannot start the act of vomiting. The chemoreceptor trigger zone is usually associated with chemically induced vomiting, and can be activated by a number of different drugs, as well as other stimuli such as bacterial toxins and radiation. Similarly, the vomiting associated with pregnancy is probably initiated through the chemoreceptor trigger zone. Vomiting should be distinguished from regurgitation, which refers to the expulsion of food in the absence of nausea, and without the abdominal muscular contractions associated with vomiting.

Nausea and vomiting are associated with many organic and functional disorders. Many acute abdominal emergencies such as acute appendicitis, acute cholecystitis, intestinal obstruction, or peritonitis may be associated with nausea and vomiting, as well as other disorders of the alimentary tract. Viral, bacterial, and parasitic infections of the GI tract are typically associated with severe nausea and vomiting.

One of the most common causes of vomiting in children is viral gastroenteritis caused by rotavirus. Vomiting in infants may be associated with something as simple as overfeeding, too rapid feeding, inadequate burping, or lying down too soon after feeding. Vomiting in a newborn on the first day of life may suggest upper digestive tract obstruction or increase in intracranial pressure.

Another type of nausea called anticipatory nausea and vomiting may be caused either by specific stimuli associated with the administration of noxious agents or by the anxiety associated with the related treatments. Many patients demonstrate both types. The most often accepted theory for this pattern of conditioning is that by repeated pairing of chemotherapy and it's after effects, certain odors, sounds, and settings associated wit