Nausea

Nausea | 
Specialty; Gastroenterology
Nausea is an unpleasant, diffuse sensation of unease and discomfort, often perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged, and has been described as placing discomfort on the chest, upper abdomen, or back of the throat.
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 and low blood sugar. Nausea is a side effect of many medications including chemotherapy, or morning sickness in early pregnancy. Nausea may also be caused by anxiety, disgust and depression.
Medications taken to prevent and treat nausea are called antiemetics. The most commonly prescribed antiemetics in the US are promethazine, metoclopramide and the newer, extremely effective ondansetron. The word nausea is from Latin nausea, from Greek ναυσία – nausia, "ναυτία" – nautia, motion sickness, "feeling sick or queasy".
Causes
Gastrointestinal infections (37%) and food poisoning are the two most common causes of acute nausea and vomiting. Side effects from medications (3%) 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, 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
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.
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 women 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.
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, carbon monoxide poisoning and many others.
Comprehensive list
Inside the abdomen
Obstructing disorders
  • Pyloric obstruction
  • Small bowel obstruction
  • Colonic obstruction
  • Superior mesenteric artery syndrome
Enteric infections
  • Viral infection
  • Bacterial infection
Inflammatory diseases
  • Celiac disease
  • Cholecystitis
  • Pancreatitis
  • Appendicitis
  • Hepatitis
Sensorimotor dysfunction
  • Gastroparesis
  • Intestinal pseudo-obstruction
  • Gastroesophageal reflux disease
  • Irritable bowel syndrome
  • Chronic idiopathic nausea
  • Functional vomiting
  • Cyclic vomiting syndrome
Other
  • Non-celiac gluten sensitivity
  • Biliary colic
  • Abdominal irradiation
Outside the abdomen
Cardiopulmonary
  • Cardiomyopathy
  • Myocardial infarction (heart attack)
Inner-ear diseases
  • Motion sickness
  • Labyrinthitis
  • Malignancy
Intracerebral disorders
  • Malignancy
  • Hemorrhage
  • Abscess
  • Hydrocephalus
  • Meningitis
  • Encephalitis
Psychiatric illnesses
  • Anorexia and bulimia nervosa
  • Depression
Other
  • Post-operative vomiting
Medications and metabolic disorders
Drugs
  • Chemotherapy
  • Antibiotics
  • Antiarrhythmics
  • Digoxin
  • Oral hypoglycemic medications
  • Oral contraceptives
Endocrine/metabolic disease
  • Pregnancy
  • Uremia
  • Ketoacidosis
  • Thyroid and parathyroid disease
  • Adrenal insufficiency
Toxins
  • Liver failure
  • Alcohol
Pathophysiology
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 (CNS): 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 (i.e. blood or infection), and extreme emotional triggers such as anxiety.
  • Chemoreceptor trigger zone (CTZ): 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 (D2) receptors, serotonin (5HT3) receptors, and neurokinin receptors (NK1).
  • 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 (H1) receptors and acetylcholine (ACh) 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.
Treatment
If dehydration is present due to loss of fluids from severe vomiting, rehydration with oral electrolyte solutions is preferred. If this is not effective or possible, intravenous rehydration may be required. Medical care is recommended if: a person cannot keep any liquids down, has symptoms more than 2 days, is weak, has a fever, has stomach pain, vomits more than two times in a day or does not urinate for more than 8 hours.
Medications
Many pharmacologic medications are available for the treatment of nausea. There is no medication that is clearly superior to other medications for all cases of nausea. The choice of antiemetic medication may be based on the situation during which the person experiences nausea. For people with motion sickness and vertigo, antihistamines and anticholinergics such as meclizine and scopolamine are particularly effective. Nausea and vomiting associated with migraine headaches respond best to dopamine antagonists such as metoclopramide, prochlorperazine, and chlorpromazine. In cases of gastroenteritis, serotonin antagonists such as ondansetron were found to suppress nausea and vomiting, as well as reduce the need for IV fluid resuscitation. The combination of pyridoxine and doxylamine is the first line treatment for pregnancy-related nausea and vomiting. Dimenhydrinate is an inexpensive and effective over the counter medication for preventing postoperative nausea and vomiting. Other factors to consider when choosing an antiemetic medication include the person's preference, side-effect profile, and cost.
Alternative medicine
In certain people, cannabinoids may be effective in reducing chemotherapy associated nausea and vomiting. Several studies have demonstrated the therapeutic effects of cannabinoids for nausea and vomiting in the advanced stages of illnesses such as cancer and AIDS.
In hospital settings topical anti-nausea gels are not indicated because of lack of research backing their efficacy. Topical gels containing lorazepam, diphenhydramine, and haloperidol are sometimes used for nausea but are not equivalent to more established therapies.
Ginger has also been shown to be potentially effective in treating several types of nausea.