Nausea and vomiting are not diseases but are symptoms of an underlying condition and can occur due to various causes, mostly harmless and rarely serious.

Nausea is the uncomfortable feeling one gets when they feel they might throw up. Vomiting is when we actually throw up. Both symptoms may occur together, but sometimes we can feel nauseous without throwing up, and sometimes people throw up without feeling nauseous

PHYSIOLOGY /MECHANISM OF VOMITING
The mechanism of vomiting has three components
1. Sensory or afferent signals are relayed from the periphery (depending on the cause) to the brain
2. In the brain these signals are received, recognized and processed
3. Efferent or effector signals (chemicals and motor) are relayed from the brain to the digestive tract causing contraction of abdominal muscles, propulsion of food or intestinal contents towards the mouth and throwing up

The part of the brain that receives afferent signals is the chemoreceptor trigger zone (CTZ) situated in the medulla. When activated, the CTZ does not by itself initiate vomiting, but relays these signals to nearby integrative vomiting centre which is responsible for causing vomiting

ASSOCIATED SYMPTOMS THAT WARRANT URGENT MEDICAL ATTENTION
• Associated chest pain or abdominal pain
• Vomiting blood or blackish material
• Vomiting bile
• Passing dark colored stool
• Severe headache and neck stiffness
• Extreme tiredness
• Unintentional weight loss
• Severe vomiting with dehydration (exhaustion, dry skin, lips and mouth, excess thirst, confusion, dizziness, muscle cramps, dark colored urine)
• Vomiting persisting or becoming worse eve after 48 hours

COMPLICATIONS OF SEVERE VOMITING
• Dehydration due to loss of fluid from the body during vomiting
• Metabolic alkalosis due to loss of stomach acid
• Starvation, malnutrition and vitamin deficiency due to protracted vomiting
• Dehiscence of surgical wound
• Aspiration of vomitus
• Decay of tooth enamel due to persistent vomiting

TREATMENT OF NAUSEA AND VOMITING
? General Measures
Avoid solid food until the symptom has passed
Try to drink sufficient amounts of clear liquid as tolerated
Bed rest
Temporarily stop medications as they may irritate the stomach and worsen the condition
Treating underlying condition such as migraine, electrolyte imbalance or stopping an offending drug
Dietary modifications (see under “prevention”) may especially help during pregnancy

? Medications
Several classes of medications are available to control nausea and vomiting. They are called antiemetics and they act by inhibiting the pathways or mechanisms involved in causing nausea and vomiting (see table above). All medications should be taken only under medical supervision

Dopamine antagonists – Drugs belonging to this class include metaclopramide and prochlorperazine. These agents stimulate motility of the upper gut without causing gastric, biliary or pancreatic secretions

Antihistamines – Example of this class of drug is promethazine. It is a long acting antihistamine with sedative and anticholinergic properties that improve antiemetic effect.

5HT3 antagonists – These drugs are used mainly to prevent or treat nausea and vomiting following surgery, cancer chemotherapy or radiation. Examples include palonosetron, granisetron, ondansetron, dolasetron and tropisetron. Since 5HT3 receptors are widely distributed both peripherally on vagal nerve terminals and centrally in the CTZ, these agents are an effective method of preventing nausea and vomiting.

Anticholinergics – Antiemetic belonging to this class is hyoscine, which is a belladonna alkaloid. Hyoscine has anti-spasmodic and anti-motility effect on the gut by opposing the action of acetylcholine

• Surgery:
Rarely surgery may be required in prolonged persistent vomiting due to bowel obstruction or increased intracranial pressure

PREVENTION OF NAUSEA & VOMITING
• Eat small frequent meals
• Avoid spicy and fried foods; consume light and bland foods eg crackers, yoghurt, noodles, steamed rice, oatmeal, steamed chicken, boiled potatoes, rice, noodles, canned peaches or other soft, bland fruits and vegetables
• Avoid beverages such as coffee, tea and alcohol as they tend to worsen nausea
• Eat slowly and rest sitting up for at least an hour after meals
• Eat foods at room temperature or cooler
• Avoid drinking water/liquids with your meal (take water between meals)
• Take rest since activity may aggravate vomiting
• Drink clear sweetened liquids such as fruit juice (avoid citrus fruits) and soda pop
• Treat cough and fever in children with OTC medicines
• Avoid eating in rooms with strong smells
• Avoid hot foods and drinks
• To avoid/reduce motion sickness, look straight ahead through the front of the car. Looking out through side windows can increase nauseous feeling

PROGNOSIS
The outlook in most cases of nausea and vomiting is good following administration of antiemetics and
treatment of underlying cause if any

Key Points
• Persons who have normal findings on examination and have an obvious cause (such as food poisoning or motion sickness) only need symptomatic treatment
• Women of childbearing age should undergo pregnancy test
• Serious causes in the abdomen and the head should be ruled out in prolonged persistent vomiting