A man leaning over the side of a bed vomiting, from a broadside entitled 'Death of Aurelio Caballero due to yellow fever in Veracruz'

Nausea and Vomiting causes and treatment

Nausea and Vomiting

Nausea is a vague, intensely disagreeable sensation of sick­ness or “queasiness” and is distinguished from anorexia. Vomiting often follows, as does retching (spasmodic respi­ratory and abdominal movements). Vomiting should be distinguished from regurgitation, the effortless reflux of liquid or food stomach contents; and from rumination, the chewing and swallowing of food that is regurgitated voli­tionally after meals. Nausea and vomiting are not diseases, but rather are symptoms of many different conditions.

The brainstem vomiting center is composed of a group of neuronal areas (area postrema, nucleus tractus solitar­ius, and central pattern generator) within the medulla that coordinate emesis. It may be stimulated by four different sources of afferent input:

(1) Afferent vagal fibers from the gastrointestinal viscera are rich in serotonin 5-HT3 recep­tors; these may be stimulated by biliary or gastrointestinal distention, mucosal or peritoneal irritation, or infections.

(2) Fibers of the vestibular system, which have high con­centrations of histamine H1 and muscarinic cholinergic receptors.

(3) Higher central nervous system centers (amygdala); here, certain sights, smells, or emotional expe­riences may induce vomiting. For example, patients receiv­ing chemotherapy may start vomiting in anticipation of its administration.

(4) The chemoreceptor trigger zone, located outside the blood-brain barrier in the area pos­trema of the medulla, which is rich in opioid, serotonin 5-HT3, neurokinin 1 (NK1) and dopamine D2 receptors. This region may be stimulated by drugs and chemothera­peutic agents, toxins, hypoxia, uremia, acidosis, and radia­tion therapy.

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Signs and symptoms

Acute symptoms without abdominal pain are typically caused by food poisoning, infectious gastroenteritis, drugs, or systemic illness. Inquiry should be made into recent changes in medications, diet, other intestinal symptoms, or similar illnesses in family members. The acute onset of severe pain and vomiting suggests peritoneal irritation, acute gastric or intestinal obstruction, or pancreaticobili­ary disease.

Persistent vomiting suggests pregnancy, gastric outlet obstruction, gastroparesis, intestinal dysmotility, psychogenic disorders, and central nervous system or sys­temic disorders. Vomiting that occurs in the morning before breakfast is common with pregnancy, uremia, alco­hol intake, and increased intracranial pressure.

Vomiting immediately after meals strongly suggests bulimia or psy­chogenic causes. Vomiting of undigested food one to sev­eral hours after meals is characteristic of gastroparesis or a gastric outlet obstruction; physical examination may reveal a succussion splash. Patients with acute or chronic symptoms should be asked about neurologic symptoms (eg, headache, stiff neck, vertigo, and focal paresthesias or weakness) that suggest a central nervous system cause.

Diagnosis

With vomiting that is severe or protracted, serum electro­lytes should be obtained to look for hypokalemia, azote­mia, or metabolic alkalosis resulting from loss of gastric contents. Flat and upright abdominal radiographs or abdominal CT are obtained in patients with severe pain or suspicion of mechanical obstruction to look for free intra­peritoneal air or dilated loops of small bowel. The cause of gastric outlet obstruction is best demonstrated by upper endoscopy, and the cause of small intestinal obstruction is best demonstrated with abdominal CT imaging.

Gastropa­resis is confirmed by nuclear scintigraphic studies or 13C-octanoic acid breath tests, which show delayed gastric emptying and either upper endoscopy or barium upper gastrointestinal series showing no evidence of mechanical gastric outlet obstruction. Abnormal liver biochemical tests or elevated amylase or lipase suggest pancreaticobili­ary disease, which may be investigated with an abdominal sonogram or CT scan. Central nervous system causes are best evaluated with either head CT or MRI.

Treatment

Most causes of acute vomiting are mild, self-limited, and require no specific treatment. Patients should ingest clear liquids (broths, tea, soups, carbonated beverages) and small quantities of dry foods (soda crackers). Ginger may be an effective nonpharmacologic treatment. For more severe acute vomiting, hospitalization may be required. Patients unable to eat and losing gastric fluids may become dehy­drated, resulting in hypokalemia with metabolic alkalosis. Intravenous 0.45% saline solution with 20 mEq/L of potas­sium chloride is given in most cases to maintain hydration. A nasogastric suction tube for gastric or mechanical small bowel obstruction improves patient comfort and permits monitoring of fluid loss.

Antiemetic Medications

Medications may be given either to prevent or to control vomiting. Combinations of drugs from different classes may provide better control of symptoms with less toxicity in some patients.

Serotonin 5-HT3-receptor antagonists: Ondansetron, granisetron, dolasetron, and palonosetron are effective in preventing chemotherapy- and radiation-induced emesis when initiated prior to treatment.

Corticosteroids: Corticosteroids (eg, dexamethasone) have antiemetic properties, but the basis for these effects is unknown. These agents enhance the efficacy of serotonin receptor antagonists for preventing acute and delayed nau­sea and vomiting in patients receiving moderately to highly emetogenic chemotherapy regimens.

Neurokinin receptor antagonists: Aprepitant, fosapre­pitant, and rolapitant are highly selective antagonists for NK1-receptors in the area postrema. They are used in com­bination with corticosteroids and serotonin antagonists for the prevention of acute and delayed nausea and vomiting with highly emetogenic chemotherapy regimens. Netupitant is another oral NK1-receptor antagonist that is administered in a fixed-dose combination with palonosetron.

Dopamine antagonists: The phenothiazines, butyro­phenones, and substituted benzamides (eg, prochlorpera­zine, promethazine) have antiemetic properties that are due to dopaminergic blockade as well as to their sedative effects. High doses of these agents are associated with anti­dopaminergic side effects, including extrapyramidal reac­tions and depression. With the advent of more effective and safer antiemetics, these agents are infrequently used, mainly in outpatients with minor, self-limited symptoms.

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Antihistamines and anticholinergics: These drugs (eg, meclizine, dimenhydrinate, transdermal scopolamine) may be valuable in the prevention of vomiting arising from stimu­lation of the labyrinth, ie, motion sickness, vertigo, and migraines. They may induce drowsiness. A combination of oral vitamin B6 and doxylamine is recommended by the American College of Obstetricians and Gynecologists as first-line therapy for nausea and vomiting during pregnancy.

Cannabinoids: Marijuana has been used widely as an appetite stimulant and antiemetic. Pure Delta9-tetrahydro­cannabinol (THC) is the major active ingredient in marijuana and the most psychoactive and is available by prescription as dronabinol. In doses of 5–15 mg/m2, oral dronabinol is effective in treating nausea associated with chemotherapy, but it is associated with central nervous system side effects in most patients.

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