Nausea and Vomiting

Neurophysiology: key brain regions of N/V

Vomiting center, NTS (nucleus tractus solitarius), CTZ (chemoreceptor trigger zone), higher cortical centers.

Phases of vomiting

Phase 1: nausea, reverse peristalsis, pyloric relaxation. Phase 2: pylorospasm + forceful contraction.

Causes of nausea/vomiting

Enteric infections, pregnancy, gastric inflammation/ulcers, drugs, obstruction, gastroparesis, metabolic disorders, neurologic disease.

Enteric infections

Most common cause of acute nausea/vomiting; self‑limited.

Pregnancy nausea

Morning sickness; hyperemesis gravidarum in 1st trimester.

Gastric inflammation causes

H. pylori, NSAIDs, bile reflux, peptic ulcer disease.

Drugs that induce nausea

Chemo, opioids, NSAIDs, antibiotics, oral iron.

Obstructive causes of N/V

Pyloric stenosis, SBO, Crohn’s, pseudo‑obstruction, colonic inertia.

Metabolic causes of N/V

Adrenal insufficiency, hyperglycemia, acidosis, uremia.

Neurologic causes of N/V

Migraine, vestibular disease, dysautonomia, tumors.

Serious consequences of vomiting

Dehydration, hypokalemia, metabolic alkalosis, aspiration pneumonia, Mallory‑Weiss tear, Boerhaave syndrome, malnutrition.

Treatment goals with vomiting + nausea

1) Control vomiting for hydration; 2) Suppress nausea; 3) Treat underlying cause.

Medication strategy

Scheduled dosing > PRN; start with mild side‑effect drugs; combine classes if needed.

Meds for acid suppression

PPI or H2 blocker if gastric inflammation present.

5‑HT3 antagonists

Ondansetron, granisetron, dolasetron, palonosetron; best for chemo‑induced nausea; SE: constipation, headache.

Antihistamines to treat N/V

Promethazine, meclizine, dimenhydrinate, scopolamine; good for motion sickness; SE: sedation, dry mouth.

Dopamine antagonists to treat N/V

Prochlorperazine, metoclopramide, domperidone; SE: dystonia, EPS, hyperprolactinemia.

Dronabinol moa + use

Dronabinol, CB1 cannabinoid receptor agonist; used for refractory chemo nausea; SE: euphoria, tachycardia.

Ginger

Contains natural 5‑HT3 antagonists; used for pregnancy nausea.

Mallory‑Weiss tear

Partial mucosal tear from retching; causes hematemesis. (boerhaave is full tear, emergency)

Boerhaave syndrome

Full‑thickness esophageal rupture after forceful vomiting; surgical emergency.