Vomiting


Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. The substance so produced is also known as vomit or vomitus.
Vomiting can be the result of ailments like food poisoning, gastroenteritis, pregnancy, motion sickness, or hangover; or it can be an after effect of diseases such as brain tumors, elevated intracranial pressure, or overexposure to ionizing radiation. The feeling that one is about to vomit is called nausea; it often precedes, but does not always lead to vomiting. Impairment due to alcohol or anesthesia can cause inhalation of vomit. In severe cases, where dehydration develops, intravenous fluid may be required. Antiemetics are sometimes necessary to suppress nausea and vomiting. Self-induced vomiting can be a component of an eating disorder such as bulimia nervosa, and is itself now classified as an eating disorder on its own, purging disorder.

Complications

Aspiration

Vomiting is dangerous if gastric content enters the respiratory tract. Under normal circumstances, the gag reflex and coughing prevent this from occurring; however, these protective reflexes are compromised in persons who are under the influence of certain substances or even mildly anesthetized. The individual may choke and asphyxiate or develop aspiration pneumonia.

Dehydration and electrolyte imbalance

Prolonged and excessive vomiting depletes the body of water, and may alter the electrolyte status. Gastric vomiting leads to the loss of acid and chloride directly. Combined with the resulting alkaline tide, this leads to hypochloremic metabolic alkalosis and often hypokalemia. The hypokalemia is an indirect result of the kidney compensating for the loss of acid. With the loss of intake of food the individual may eventually become cachectic. A less frequent occurrence results from a vomiting of intestinal contents, including bile acids and.

Mallory–Weiss tear

Repeated or profuse vomiting may cause erosions to the esophagus or small tears in the esophageal mucosa. This may become apparent if fresh red blood is mixed with vomit after several episodes.

Dentistry

Recurrent vomiting, such as observed in bulimia nervosa or more rarely anorexia nervosa, may lead to the destruction of the tooth enamel due to the acidity of the vomit. Digestive enzymes can also have a negative effect on oral health, by degrading the tissue of the gums.

Pathophysiology

Receptors on the floor of the fourth ventricle of the brain represent a chemoreceptor trigger zone, known as the area postrema, stimulation of which can lead to vomiting. The area postrema is a circumventricular organ and as such lies outside the blood–brain barrier; it can therefore be stimulated by blood-borne drugs that can stimulate vomiting or inhibit it.
There are various sources of input to the vomiting center:
  • The chemoreceptor trigger zone at the base of the fourth ventricle has numerous dopamine D2 receptors, serotonin 5-HT3 receptors, opioid receptors, acetylcholine receptors, and receptors for substance P. Stimulation of different receptors are involved in different pathways leading to emesis, in the final common pathway substance P appears involved.
  • The vestibular system, which sends information to the brain via cranial nerve VIII, plays a major role in motion sickness, and is rich in muscarinic receptors and histamine H1 receptors.
  • The cranial nerve X is activated when the pharynx is irritated, leading to a gag reflex.
  • The vagal and enteric nervous system inputs transmit information regarding the state of the gastrointestinal system. Irritation of the GI mucosa by chemotherapy, radiation, distention, or acute infectious gastroenteritis activates the 5-HT3 receptors of these inputs.
  • The CNS mediates vomiting that arises from psychiatric disorders and stress from higher brain centers.
  • The medulla plays an important role for triggering the vomiting act.
The vomiting act encompasses three types of outputs initiated by the chemoreceptor trigger zone: Motor, parasympathetic nervous system, and sympathetic nervous system. They are as follows:
The vomiting act has two phases. In the retching phase, the abdominal muscles undergo a few rounds of coordinated contractions together with the diaphragm and the muscles used in respiratory inspiration. For this reason, an individual may confuse this phase with an episode of violent hiccups. In this retching phase, nothing has yet been expelled. In the next phase, also termed the expulsive phase, intense pressure is formed in the stomach brought about by enormous shifts in both the diaphragm and the abdomen. These shifts are, in essence, vigorous contractions of these muscles that last for extended periods of time—much longer than a normal period of muscular contraction. The pressure is then suddenly released when the upper esophageal sphincter relaxes resulting in the expulsion of gastric contents. As the mouth and nasal cavity are connected via the back of the throat, particularly forceful vomiting, or producing large quantities of vomit may result in material being ejected through the nostrils in addition to the mouth. Individuals who do not regularly exercise their abdominal muscles may experience pain in those muscles for a few days. The decrease in pressure and the release of endorphins into the bloodstream after the expulsion causes the vomiter to feel relief almost immediately after vomiting.

Contents

and likewise vomit are highly acidic. Recent food intake appears in the gastric vomit. Irrespective of the content, vomit tends to be malodorous.
The content of the vomitus may be of medical interest. Fresh blood in the vomit is termed hematemesis. Altered blood bears resemblance to coffee grounds and, when this matter is identified, the term coffee-ground vomiting is used. Bile can enter the vomit during subsequent heaves due to duodenal contraction if the vomiting is severe. Fecal vomiting is often a consequence of intestinal obstruction or a gastrocolic fistula and is treated as a warning sign of this potentially serious problem.
If the vomiting reflex continues for an extended period with no appreciable vomitus, the condition is known as non-productive emesis or "dry heaves", which can be painful and debilitating.
;Color of vomit
  • Bright red in the vomit suggests bleeding from the esophagus
  • Dark red vomit with liver-like clots suggests profuse bleeding in the stomach, such as from a perforated ulcer
  • Coffee-ground-like vomit suggests less severe bleeding in the stomach because the gastric acid has had time to change the composition of the blood
  • Yellow or green vomit suggests bile, indicating that the pyloric valve is open and bile is flowing into the stomach from the duodenum. This may occur during successive episodes of vomiting after the stomach contents have been completely expelled.

    Causes

Vomiting may be due to a large number of causes, and protracted vomiting has a long differential diagnosis.

Digestive tract

Causes in the digestive tract
Causes in the sensory system:
Causes in the brain:
Metabolic disturbances :
Pregnancy:
Drug reaction :
High altitude:
  • Altitude sickness
Illness :
Psychiatric/behavioral:
An emetic, such as syrup of ipecac, is a substance that induces vomiting when administered orally or by injection. An emetic is used medically when a substance has been ingested and must be expelled from the body immediately. For this reason, many toxic and easily digestible products such as rat poison contain an emetic. This presents no problem for the effectiveness of the rodenticide as rodents are unable to vomit. Inducing vomiting can remove the substance before it is absorbed into the body.
Emetics can be divided into two categories: those which produce their effect by acting on the vomiting center in the medulla, and those which act directly on the stomach itself. Some emetics, such as ipecac, fall into both categories: they initially act directly on the stomach, while their further and more vigorous effect occurs by stimulation of the medullary center.
Salt water and mustard water, which act directly on the stomach, have been used since ancient times as emetics. Care must be taken with salt, as excessive intake can potentially be harmful.
Copper sulfate was also used in the past as an emetic. It is now considered too toxic for this use.
Hydrogen peroxide is used as an emetic in veterinary practice.