Nausea and vomiting overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D.  Associate Editor(s)-in-Chief: Vishnu Vardhan Serla M.B.B.S. 
Nausea (Latin: Nausea, Greek: Template:Polytonic, "sea-sickness") is an ‘unpleasant painless subjective feeling that one will imminently vomit’. Nausea is often indicative of an underlying condition elsewhere in the body. Travel sickness, which is due to confusion between perceived movement and actual movement, is an example. The sense of equilibrium lies in the ear and works together with eyesight. When these two don't "agree" to what extent the body is actually moving the symptom is presented as nausea even though the stomach itself has nothing to do with the situation. Nausea is also an adverse effect of many drugs. Nausea may also be an effect of a large intake of sugary foods. In medicine, nausea can be a problem during some chemotherapy regimens and following general anesthesia. Nausea is also a common symptom of pregnancy. Mild nausea experienced during pregnancy can be normal, and should not be considered an immediate cause for alarm. Vomiting (also throwing up or emesis) is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose resulting from contractions of gut and thoracoabdominal wall musculature. 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 but 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 to replace fluid volume. The medical branch investigating vomiting, emetics, and antiemetics is called emetology.
The medical term ‘nausea’ is derived from the classical Greek terms ναυτια and ναυσια, which designated the signs and symptoms of seasickness. The descriptions of the development of seasickness in monographs from the latter half of the 19th and early 20th centuries provide a context for understanding the evolution of the demarcation of symptom clusters associated with the original term ‘nausea”. The term ‘nausea’ has been used to denote both a disorder (diagnosis of seasickness) and a symptom (or symptom cluster) associated with other disorders. This pattern also appeared for terms for vertigo, such as ‘vertigine’, dinos, scotomatikos and skotodininos. Hence, one must ask whether the term nausea denoted seasickness explicitly or whether it denoted the appearance of a ‘cluster of signs and symptoms of seasickness’ as a component of other primary disorders.
Nausea and vomiting can be classified into acute or chronic
Acute nausea and vomiting
Acute vomiting which typically lasts from a few hours to few days is the most common presentation in the emergency department. Acute vomiting needs an extensive workup to exclude life-threatening conditions like bowel obstruction, mesenteric ischemia, acute pancreatitis, and possibly myocardial infarction.
Chronic nausea and vomiting
Chronic vomiting which lasts from weeks to months is initially evaluated in an outpatient setting.
It is understood that nausea and vomiting are complex and encompass psychological states, the central nervous system, the autonomic nervous system, gastric dysrhythmias, and the endocrine system. Each individual has a threshold for nausea that changes minute by minute. At any given moment, the threshold depends on the interaction of certain inherent factors of the individual with the more changeable psychological states of anxiety, anticipation, expectation, and adaptation. Stimuli giving rise to nausea and vomiting originate from visceral, vestibular, and chemoreceptor trigger zone inputs which are mediated by serotonin/dopamine, histamine/acetylcholine, and serotonin/dopamine, respectively.
Life threatening causes of nausea and vomiting include acute coronary syndrome, anaphylaxis, and heart failure. Other common causes of nausea and vomiting are food allergies, food poisoning, gastroenteritis, and gastroesophageal reflux.
Differentiating Nausea and vomiting from Other Diseases
Epidemiology and Demographics
Natural History, Complications, and Prognosis
Diagnostic Study of Choice
History and Symptoms
Echocardiography and Ultrasound
ECG is done to rule out an inferior MI or arrhythmia.