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Sunday, August 17, 2025

Vomiting


Introduction

Vomiting, or emesis, is the forceful expulsion of stomach contents through the mouth due to coordinated muscular contractions of the diaphragm, abdominal wall, and gastrointestinal tract. It is usually preceded by nausea and retching and may be acute or chronic. Vomiting is a non-specific symptom and can result from a wide spectrum of causes, ranging from benign self-limiting illnesses to life-threatening conditions.

While occasional vomiting may occur with minor illnesses, persistent or severe vomiting requires careful evaluation to determine the underlying cause, correct complications such as dehydration or electrolyte imbalance, and initiate appropriate therapy.

Causes of Vomiting

1. Gastrointestinal Disorders

  • Infections: Viral gastroenteritis, food poisoning, bacterial enteritis.

  • Obstruction: Small bowel obstruction, gastric outlet obstruction, pyloric stenosis.

  • Inflammatory conditions: Appendicitis, cholecystitis, pancreatitis, peptic ulcer disease.

  • Hepatobiliary disease: Hepatitis, gallstones.

2. Central Nervous System Causes

  • Raised intracranial pressure: Brain tumors, meningitis, encephalitis, intracranial hemorrhage.

  • Vestibular disorders: Motion sickness, labyrinthitis, Meniere’s disease.

  • Migraine-associated vomiting.

3. Metabolic and Endocrine Causes

  • Diabetic ketoacidosis (DKA).

  • Addisonian crisis.

  • Uremia (chronic kidney disease).

  • Hypercalcemia, hyponatremia.

4. Medications and Toxins

  • Chemotherapy agents (cisplatin, cyclophosphamide).

  • Opiates, digoxin, theophylline.

  • Alcohol intoxication.

5. Pregnancy

  • Morning sickness (common in first trimester).

  • Hyperemesis gravidarum: Severe, persistent vomiting with dehydration and weight loss.

6. Psychiatric and Functional Causes

  • Eating disorders (bulimia nervosa).

  • Psychogenic vomiting.

Pathophysiology

Vomiting is coordinated by the vomiting center in the medulla oblongata, which receives input from:

  • Chemoreceptor trigger zone (CTZ): Sensitive to drugs, toxins, metabolic changes.

  • Vestibular system: Motion and balance disturbances (histamine and acetylcholine mediated).

  • Cerebral cortex: Higher brain centers (fear, smell, sight).

  • Visceral afferents: Gastrointestinal irritation or distension.

Neurotransmitters involved include dopamine (D2), serotonin (5-HT3), histamine (H1), acetylcholine (M1), and substance P (NK1), forming the basis of antiemetic therapy.

Clinical Presentation

  • Main symptom: Expulsion of gastric contents.

  • Associated features:

    • Nausea, retching.

    • Abdominal pain or distension.

    • Headache, photophobia (CNS causes).

    • Polyuria, polydipsia (diabetes).

    • Jaundice (hepatitis).

Red-flag signs:

  • Vomiting blood (hematemesis).

  • Projectile vomiting (pyloric stenosis, raised ICP).

  • Severe dehydration (dry mouth, sunken eyes, oliguria).

  • Altered mental status.

Diagnosis

1. History and Examination

  • Onset, frequency, characteristics (bilious, bloody, projectile).

  • Associated symptoms (diarrhea, abdominal pain, headache, fever).

  • Drug history, pregnancy status, travel and dietary history.

2. Investigations (guided by suspicion)

  • Blood tests: CBC, electrolytes, renal/liver function, glucose, calcium.

  • Urine tests: Ketones, pregnancy test.

  • Imaging: Abdominal X-ray, ultrasound, CT abdomen (for obstruction).

  • Endoscopy: If GI bleeding suspected.

  • Lumbar puncture: If meningitis/encephalitis suspected.

Treatment

1. General Measures

  • Identify and treat the underlying cause.

  • Rehydration: Oral rehydration solution (ORS) for mild cases; IV fluids (normal saline, Ringer’s lactate) for severe dehydration.

  • Gradual reintroduction of diet (clear fluids, bland foods).

2. Pharmacological Treatment

a) Dopamine (D2) Receptor Antagonists

  • Metoclopramide:

    • Dose: 10 mg orally/IV/IM up to three times daily.

    • Useful in diabetic gastroparesis, post-operative nausea.

    • Contraindication: Parkinson’s disease, risk of extrapyramidal effects.

  • Domperidone:

    • Dose: 10 mg orally three times daily.

    • Fewer CNS side effects.

b) Serotonin (5-HT3) Receptor Antagonists

  • Ondansetron:

    • Dose: 4–8 mg orally or IV every 8–12 hours.

    • Highly effective in chemotherapy, post-operative vomiting.

c) Antihistamines (H1 receptor antagonists)

  • Cyclizine: 50 mg orally or IV up to three times daily.

  • Promethazine: 25 mg orally or IM once daily at night.

  • Useful in motion sickness, vestibular disorders.

d) Anticholinergics (M1 receptor antagonists)

  • Hyoscine hydrobromide (Scopolamine): 0.3–0.6 mg IM/IV every 6–8 hours or transdermal patch (1.5 mg every 72 hours).

  • Used for motion sickness.

e) Neurokinin-1 (NK1) Receptor Antagonists

  • Aprepitant: 125 mg orally on day 1, then 80 mg daily for 2 days.

  • For chemotherapy-induced nausea and vomiting (CINV).

f) Other Agents

  • Corticosteroids (Dexamethasone 4–8 mg IV): Often combined with 5-HT3 antagonists in CINV.

  • Benzodiazepines (Lorazepam 0.5–2 mg): For anticipatory nausea in chemotherapy.

Special Situations

  • Pregnancy (Hyperemesis gravidarum):

    • Pyridoxine (Vitamin B6) 25 mg orally three times daily.

    • Doxylamine 10 mg orally at night.

    • If severe: Metoclopramide or Ondansetron under supervision.

  • Children:

    • Oral rehydration is key.

    • Ondansetron 0.15 mg/kg orally/IV (max 8 mg) in acute gastroenteritis.

  • Raised Intracranial Pressure:

    • Mannitol, dexamethasone, and neurosurgical evaluation required.

Precautions

  • Avoid antiemetics in undiagnosed acute abdomen until surgical cause is excluded.

  • Metoclopramide and prochlorperazine may cause extrapyramidal side effects.

  • Ondansetron may prolong QT interval; caution in patients with cardiac disease.

  • Antihistamines and anticholinergics cause sedation, dry mouth, blurred vision.

Drug Interactions

  • Metoclopramide + Antipsychotics (haloperidol): Additive risk of extrapyramidal reactions.

  • Ondansetron + SSRIs (fluoxetine, sertraline): Risk of serotonin syndrome.

  • Domperidone + QT-prolonging drugs (macrolides, fluoroquinolones): Risk of arrhythmias.

  • Cyclizine/Promethazine + alcohol or sedatives: Increased CNS depression.

  • Aprepitant + Warfarin or Oral Contraceptives: Reduced effectiveness due to CYP3A4 interactions.

Red-Flag Features Requiring Urgent Evaluation

  • Persistent vomiting with dehydration, shock, or electrolyte imbalance.

  • Vomiting blood (hematemesis) or coffee-ground vomit.

  • Projectile vomiting in infants (pyloric stenosis).

  • Severe abdominal pain with distension (bowel obstruction).

  • Vomiting associated with severe headache, altered consciousness (raised ICP, meningitis).

  • Inability to tolerate fluids for >24 hours.





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