KEY CLINICAL UPDATES IN NAUSEA & VOMITING
A 2020 American Gastroenterological Association meta-analysis reported a pooled prevalence of nausea or vomiting (usually mild) in 7.8% of patients with acute COVID-19.
Up to 16% of patients may present with gastrointestinal symptoms (anorexia, nausea, diarrhea) in the absence of respiratory symptoms.
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.
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. Although the causes of nausea and vomiting are many, a simplified list is provided in Table 15–1.
Table 15–1.Causes of nausea and vomiting. ||Download (.pdf) Table 15–1. Causes of nausea and vomiting.
|Visceral afferent stimulation || |
Gastric outlet obstruction: peptic ulcer disease, malignancy, gastric volvulus
Small intestinal obstruction: adhesions, hernias, volvulus, Crohn disease, carcinomatosis
Gastroparesis: diabetic, postviral, postvagotomy
Small intestine: systemic sclerosis (scleroderma), amyloidosis, chronic intestinal pseudo-obstruction, familial myoneuropathies
Peritonitis: perforated viscus, appendicitis, spontaneous bacterial peritonitis
Viral gastroenteritis: Norwalk agent, rotavirus, COVID-19
“Food poisoning”: toxins from Bacillus cereus, Staphylococcus aureus, Clostridium perfringens
Acute systemic infections
Hepatobiliary or pancreatic disorders
Acute or chronic pancreatitis
Cholecystitis or choledocholithiasis
Topical gastrointestinal irritants
Alcohol, NSAIDs, oral antibiotics
Cardiac disease: acute myocardial infarction, heart failure
Urologic disease: stones, pyelonephritis
Vascular: chronic mesenteric ischemia, superior mesenteric artery syndrome
|Vestibular disorders || |
Labyrinthitis, Ménière syndrome, motion sickness
|CNS disorders || |
Increased intracranial pressure
CNS tumors, subdural or subarachnoid hemorrhage
Cyclical vomiting syndrome
Anticipatory vomiting, anorexia nervosa and bulimia, psychiatric disorders
|Irritation of chemoreceptor trigger zone || |
Medications and drugs
Beta-blockers, antiarrhythmics, digoxin
Diabetes medications (metformin, acarbose, pramlintide, exenatide)