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Vomiting (or emesis) is the forceful expulsion of the contents of one's stomach through the mouth. Vomiting may result from many causes, ranging from gastritis or poisoning to brain tumors, or elevated intracranial pressure (ICP). The feeling that one is about to vomit is called nausea. It usually precedes vomiting, but it does not always lead to vomiting. Antiemetics are sometimes necessary to suppress nausea and vomiting, and in severe cases where dehydration develops, intravenous fluid may need to be administered. The medical branch investigating vomiting, emetics and antiemetics is called emetology. Vomiting center Vomiting is coordinated in the vomiting center in the lateral medullary reticular formation in the medulla. Receptors on the floor of the fourth ventricle of the brain represent a chemoreceptor trigger zone, stimulation of which can lead to vomiting. The chemoreceptor zone lies outside the blood-brain barrier, and 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: Vomiting act The vomiting act encompasses three types of outputs initiated by the medulla: Motor, parasympathetic nervous system (PNS) and sympathetic nervous system (SNS). Collectively, they are as follows: The neurotransmitters that regulate vomiting are poorly understood, but inhibitors of dopamine, histamine and serotonin are all used to suppress vomiting, suggesting that these play a role in the initiation or maintenance of a vomiting cycle. Vasopressin and neurokinin may also participate. Content Since the stomach secretes acid, vomit contains a high concentration of hydronium ions and is thus strongly acidic. Recent food intake will be reflected in the gastric vomit. The content of the vomitus (vomit) may be of medical interest. Fresh blood in the vomit is termed hematemesis ("blood vomiting"). Old blood bears resemblance to coffee grounds (as the iron in the blood is oxidized), 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, and is treated as a warning sign of this potentially serious problem ("signum mali ominis"); such vomiting is sometimes called "miserere". If the vomiting reflex continues for an extended period of time with no appreciable vomitus, the condition is known as non-productive emesis or dry heaves, which can become both extremely painful and debilitating. Aspiration of vomitus Vomiting can be very dangerous if the gastric content gets into the respiratory tract. Under normal circumstances the gag reflex and coughing will prevent this to occur, however these protective reflexes are compromised in persons under narcotic influences such as alcohol or anesthesia. The individual may choke and asphyxiate or suffer an aspiration pneumonia. Dehydration and electrolyte imbalance Prolonged and excessive vomiting will deplete the body of water (dehydration) and may alter the electrolyte status. The loss of acids leads to metabolic alkalosis (increased blood pH), and the electrolyte imbalance shows hypokalemia (potassium depletion) and hypochloremia (chlorine depletion). The hypokalemia is an indirect result of the kidney compensating for the loss of acid. With the loss of intake of food the individual will become cachectic. 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: Sensory system and brain Causes in the sensory system: Causes in the brain: Metabolic disturbances (these may irritate both the stomach and the parts of the brain that coordinate vomiting): Pregnancy: Opioids, selective serotonin reuptake inhibitors, many chemotherapy drugs, and a host of other drugs may cause nausea and vomiting. Other Emetics An emetic, such as Syrup of Ipecac, is a substance that induces vomiting when administered orally or by injection. An emetic is used medically where a substance (typically poison) has been ingested and must be expelled from the body immediately. Inducing vomiting can remove the substance before it is absorbed into the body. Ipecac abuse can lead to detrimental health affects. Antiemetics An antiemetic is a drug that is effective against vomiting and nausea. Antiemetics are typically used to treat motion sickness and the side effects of some opioid analgesics and chemotherapy directed against cancer. Nausea inducement in groups It is quite common that when one person vomits, others nearby will become nauseated, particularly when smelling the vomit of others, often to the point of vomiting themselves. It is believed that this is an evolved trait among primates. Many primates in the wild will tend to browse for food in small groups. Should one member of the party react adversely to some ingested food it may be advantageous (in a survival sense) for other members of the party also to vomit. This tendency in human populations has been observed at drinking parties, where excessive consumption of alcoholic beverages may result in a number of party members vomiting nearly simultaneously, this being triggered by the initial vomiting of a single member of the party. This phenomenon has been touched on in popular culture: notorious instances appear in the films The Meaning of Life (1983) and Stand By Me (1986), while in the computer game Theme Hospital, it is referred to as a 'vomit wave' and can spread through the hospital quickly. There have also been documented cases of a single ill and vomiting individual inadvertently causing others to do so, when they are especially fearful of also becoming ill, through a form of mass hysteria. Context Most people try to contain their vomit by vomiting into a sink, toilet, or trash can, as both the act and the vomit itself are widely considered embarrassing; vomit is also difficult to clean up. On airplanes and boats, special bags are supplied for sick passengers to vomit into. Alternatively, a special disposable bag is available containing absorbent material that solidifies the vomit quickly, making it convenient and safe to keep (leakproof, puncture resistant, odorless) until there is an opportunity to dispose of it conveniently. People who vomit chronically (e.g. as part of an eating disorder such as bulimia nervosa) may devise various ways to hide this abnormality. In language As with other physiological processes involving body wastes, vomiting has taboo aspects. This is shown by the large number of colourful euphemisms for vomiting. (see: toilet humour). Reference to vomiting is often made in speech (e.g. "it makes me sick", "I need a bucket") or by gesturing to signify being disgusted by someone or something. Slang terms for the act of vomiting include: "hurling", "puking", "throwing up", "upchucking", "booting", "ralphing", "barfing", "chucking up", "sicking up", "spewing" and "chundering". In other animals | |||||||
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