Nausea


Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. It can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the throat.
Over 30 definitions of nausea were proposed in a 2011 book on the topic.
Nausea is a non-specific symptom, which means that it has many possible causes. Some common causes of nausea are gastroenteritis and other gastrointestinal disorders, food poisoning, motion sickness, dizziness, migraine, fainting, low blood sugar, anxiety, hyperthermia, dehydration and lack of sleep. Nausea is a side effect of many medications including chemotherapy, or morning sickness in early pregnancy. Nausea may also be caused by disgust and depression.
Medications taken to prevent and treat nausea and vomiting are called antiemetics. The most commonly prescribed antiemetics in the US are promethazine, metoclopramide, and the newer ondansetron. The word nausea is from Latin nausea, from Greek ναυσία – nausia, "ναυτία" – nautia, seasickness, "feeling sick or queasy", from Latin naus, Greek ναος, a ship.

Causes

and food poisoning are the two most common causes of acute nausea and vomiting. Side effects from medications and pregnancy are also relatively frequent. There are many causes of chronic nausea. Nausea and vomiting remain undiagnosed in 10% of the cases. Aside from morning sickness, there are no sex differences in complaints of nausea. After childhood, doctor consultations decrease steadily with age. Only a fraction of one percent of doctor visits by those over 65 are due to nausea.

Gastrointestinal

Gastrointestinal infection is one of the most common causes of acute nausea and vomiting. Chronic nausea may be the presentation of many gastrointestinal disorders, occasionally as the major symptom, such as gastroesophageal reflux disease, functional dyspepsia, gastritis, biliary reflux, gastroparesis, peptic ulcer, celiac disease, non-celiac gluten sensitivity, Crohn's disease, hepatitis, upper gastrointestinal malignancy, and pancreatic cancer. Uncomplicated Helicobacter pylori infection does not cause chronic nausea.

Food poisoning

usually causes an abrupt onset of nausea and vomiting one to six hours after ingestion of contaminated food and lasts for one to two days. It is due to toxins produced by bacteria in food.

Medications

Many medications can potentially cause nausea. Some of the most frequently associated include cytotoxic chemotherapy regimens for cancer and other diseases, and general anaesthetic agents. An old cure for migraine, ergotamine, is well known to cause devastating nausea in some patients; a person using it for the first time will be prescribed an antiemetic for relief if needed. Opioids commonly cause nausea too.

Pregnancy

Nausea or "morning sickness" is common during early pregnancy but may occasionally continue into the second and third trimesters. In the first trimester nearly 80 % of women have some degree of nausea. Pregnancy should therefore be considered as a possible cause of nausea in any sexually active woman of child-bearing age. While usually it is mild and self-limiting, severe cases known as hyperemesis gravidarum may require treatment.

Disequilibrium

A number of conditions involving balance such as motion sickness and vertigo can lead to nausea and vomiting.

Gynecologic

can cause nausea.

Psychiatric

Nausea may be caused by depression, anxiety disorders and eating disorders.

Potentially serious

While most causes of nausea are not serious, some serious conditions are associated with nausea. These include pancreatitis, small bowel obstruction, appendicitis, cholecystitis, hepatitis, Addisonian crisis, diabetic ketoacidosis, increased intracranial pressure, spontaneous intracranial hypotension, brain tumors, meningitis, heart attack, rabies, carbon monoxide poisoning and many others.

Comprehensive list

Inside the abdomen

Obstructing disorders
Enteric infections
Inflammatory diseases
Sensorimotor dysfunction
Other
Cardiopulmonary
Inner-ear diseases
Intracerebral disorders
Psychiatric illnesses
Other
Drugs
Endocrine/metabolic disease
Toxins
Research on nausea and vomiting has relied on using animal models to mimic the anatomy and neuropharmacologic features of the human body. The physiologic mechanism of nausea is a complex process that has yet to be fully elucidated. There are four general pathways that are activated by specific triggers in the human body that go on to create the sensation of nausea and vomiting.
  • Central nervous system : Stimuli can affect areas of the CNS including the cerebral cortex and the limbic system. These areas are activated by elevated intracranial pressure, irritation of the meninges, and extreme emotional triggers such as anxiety. The supratentorial region is also responsible for the sensation of nausea.
  • Chemoreceptor trigger zone : The CTZ is located in the area postrema in the floor of the fourth ventricle within the brain. This area is outside the blood brain barrier, and is therefore readily exposed to substances circulating through the blood and cerebral spinal fluid. Common triggers of the CTZ include metabolic abnormalities, toxins, and medications. Activation of the CTZ is mediated by dopamine receptors, serotonin receptors, and neurokinin receptors.
  • Vestibular system: This system is activated by disturbances to the vestibular apparatus in the inner ear. These include movements that cause motion sickness and dizziness. This pathway is triggered via histamine receptors and acetylcholine receptors.
  • Peripheral Pathways: These pathways are triggered via chemoreceptors and mechanoreceptors in the gastrointestinal tract, as well as other organs such as the heart and kidneys. Common activators of these pathways include toxins present in the gastrointestinal lumen and distension of the gastrointestinal lumen from blockage or dysmotility of the bowels. Signals from these pathways travel via multiple neural tracts including the vagus, glossopharyngeal, splanchnic, and sympathetic nerves.
Signals from any of these pathways then travel to the brainstem, activating several structures including the nucleus of the solitary tract, the dorsal motor nucleus of the vagus, and central pattern generator. These structures go on to signal various downstream effects of nausea and vomiting. The body's motor muscle responses involve halting the muscles of the gastrointestinal tract, and in fact causing reversed propulsion of gastric contents towards the mouth while increasing abdominal muscle contraction. Autonomic effects involve increased salivation and the sensation of feeling faint that often occurs with nausea and vomiting.

Pre-nausea pathophysiology

It has been described that alterations in heart rate can occur as well as the release of vasopressin from the posterior pituitary.

Diagnosis

Patient history

Taking a thorough patient history may reveal important clues to the cause of nausea and vomiting. If the patient's symptoms have an acute onset, then drugs, toxins, and infections are likely. In contrast, a long-standing history of nausea will point towards a chronic illness as the culprit. The timing of nausea and vomiting after eating food is an important factor to pay attention to. Symptoms that occur within an hour of eating may indicate an obstruction proximal to the small intestine, such as gastroparesis or pyloric stenosis. An obstruction further down in the intestine or colon will cause delayed vomiting. An infectious cause of nausea and vomiting such as gastroenteritis may present several hours to days after the food was ingested. The contents of the emesis is a valuable clue towards determining the cause. Bits of fecal matter in the emesis indicate obstruction in the distal intestine or the colon. Emesis that is of a bilious nature localizes the obstruction to a point past the stomach. Emesis of undigested food points to an obstruction prior to the gastric outlet, such as achalasia or Zenker's diverticulum. If patient experiences reduced abdominal pain after vomiting, then obstruction is a likely etiology. However, vomiting does not relieve the pain brought on by pancreatitis or cholecystitis.

Physical exam

It is important to watch out for signs of dehydration, such as orthostatic hypotension and loss of skin turgor. Auscultation of the abdomen can produce several clues to the cause of nausea and vomiting. A high-pitched tinkling sound indicates possible bowel obstruction, while a splashing "succussion" sound is more indicative of gastric outlet obstruction. Eliciting pain on the abdominal exam when pressing on the patient may indicate an inflammatory process. Signs such as papilledema, visual field losses, or focal neurological deficits are red flag signs for elevated intracranial pressure.