Vomiting

Forceful expulsion of stomach contents through the mouth

Vomiting is a complex reflex response that involves the brain, digestive system, and nervous system.

Vomiting, also known as emesis, is the involuntary and forceful expulsion of stomach contents through the mouth, and occasionally through the nose. It is a protective reflex controlled by the brainstem that serves to expel harmful substances, toxins, or irritants from the digestive system.

Causes

Vomiting can result from a wide range of conditions, including:

• Gastrointestinal disorders – Gastroenteritis, food poisoning, peptic ulcer disease, appendicitis, gastroesophageal reflux disease (GERD).
• Neurological conditions – Migraine, head trauma, brain tumors, intracranial pressure increase.
• Pregnancy – Commonly in the form of morning sickness or hyperemesis gravidarum.
• Toxicity and infections – Foodborne illnesses, drug overdose, alcohol poisoning, or systemic infections like sepsis.
• Psychological factors – Anxiety, stress, eating disorders (e.g., bulimia nervosa).
• Medications and treatments – Chemotherapy, anesthesia, radiation therapy, opioids.
• Motion sickness – Disturbance in the inner ear balance system due to movement (e.g., car, boat, plane).

Pathophysiology

The act of vomiting is a complex reflex controlled by the vomiting center in the medulla oblongata of the brainstem. The vomiting process is triggered by:

• The chemoreceptor trigger zone (CTZ) – Located in the brainstem, it detects toxins and chemical irritants.
• The gastrointestinal tract – Sends signals via the vagus nerve in response to irritation, distension, or infection.
• Higher brain centers – Psychological stimuli such as fear, anxiety, or unpleasant sights/smells.
• The vestibular system – Controls balance and motion detection, contributing to motion sickness.

Phases of Vomiting 1. Nausea – Subjective feeling of discomfort and urge to vomit. 2. Retching (Dry heaving) – Rhythmic contractions of abdominal muscles without expelling contents. 3. Expulsion – Sudden forceful contraction of abdominal muscles, opening of the lower esophageal sphincter, and expulsion of stomach contents.

Clinical Significance

Vomiting can be a symptom of many conditions, ranging from minor to life-threatening. Chronic or frequent vomiting can lead to:

• Dehydration – Loss of fluids leading to dizziness, dry mouth, and weakness.
• Electrolyte imbalance – Deficiency of sodium, potassium, and chloride, causing muscle weakness and irregular heartbeat.
• Aspiration pneumonia – Inhalation of vomit into the lungs, leading to lung infection.
• Mallory-Weiss syndrome – Tears in the esophagus due to forceful retching.
• Tooth enamel erosion – Chronic exposure to stomach acid can wear down teeth.

Treatment

Treatment depends on the underlying cause. Common management approaches include:

1. Symptomatic Treatment

• Antiemetics (anti-nausea medications):
• Ondansetron (Zofran) – Used for chemotherapy-induced nausea.
• Metoclopramide (Reglan) – Helps gastric motility.
• Promethazine (Phenergan) – Commonly used for motion sickness and gastroenteritis.
• Rehydration therapy:
• Oral Rehydration Solutions (ORS) for mild dehydration.
• Intravenous (IV) fluids in severe cases.
• Dietary adjustments:
• Bland foods (e.g., BRAT diet – Bananas, Rice, Applesauce, Toast).
• Avoidance of fatty, spicy, or dairy-rich foods.

2. Addressing Underlying Causes

• Gastrointestinal conditions – Proton pump inhibitors (PPIs) for GERD, antibiotics for infections.
• Pregnancy-related nausea – Vitamin B6, ginger, doxylamine (Diclegis).
• Motion sickness – Scopolamine patches, dimenhydrinate (Dramamine).
• Chemotherapy-induced vomiting – Combination antiemetics (5-HT3 receptor antagonists + corticosteroids + neurokinin-1 receptor antagonists).

Prevention

Preventative measures depend on the cause of vomiting:

• For food poisoning – Proper food handling and hygiene.
• For motion sickness – Avoid reading in a moving vehicle, focus on the horizon, use anti-motion sickness medications.
• For chemotherapy-induced nausea – Pre-medication with antiemetics before treatment.
• For pregnancy-related vomiting – Frequent small meals, ginger supplements, acupressure bands.

Complications

If vomiting is not properly managed, complications can arise:

• Severe dehydration – Requiring hospitalization for IV fluids.
• Malnutrition – Chronic vomiting leads to weight loss and nutrient deficiencies.
• Esophageal damage – Repeated exposure to acid can cause Barrett’s esophagus, ulcers, and strictures.
• Psychological distress – Associated with eating disorders like bulimia nervosa.

Vomiting in Other Animals

Vomiting is a defensive reflex observed in many animals, helping expel toxins or foreign objects. However, some animals cannot vomit, including:

• Rats and mice – Lack of the necessary brainstem circuits.
• Horses – Have a strong lower esophageal sphincter preventing regurgitation.
• Rabbits – Digestive system lacks the coordination needed to vomit.

Cultural and Historical Aspects

Vomiting has been referenced in various cultures:

• Ancient Rome – Used intentionally in "vomitoriums" (a misconception, as these were actually exits in amphitheaters).
• Ayurveda – Describes therapeutic vomiting ("Vamana") as part of detoxification.
• Medieval medicine – Linked to the humoral theory, where vomiting was believed to balance bodily fluids.

See Also

• Nausea
• Gastroenteritis
• Hyperemesis gravidarum
• Cyclic vomiting syndrome
• Bulimia nervosa
• Food poisoning

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