When a person suddenly “passes out” or faints while throwing up, it is medically termed syncope, a temporary loss of consciousness and muscle strength. This physiological response, while alarming, typically resolves quickly within seconds or minutes. It occurs due to a temporary reduction in blood flow to the brain.
The Body’s Response
Vomiting can trigger the vasovagal response. This response involves the vagus nerve, a long nerve that extends from the brainstem to the abdomen, influencing heart rate, blood pressure, and digestion. When stimulated, the vagus nerve can cause the heart rate to slow significantly (bradycardia) and blood vessels throughout the body to widen (vasodilation). This leads to a sudden drop in blood pressure.
As blood pressure falls, the brain receives insufficient blood flow. This lack of oxygen causes the brief loss of consciousness. The physical strain of vomiting, including forceful contractions, can further intensify these effects by impeding blood return to the heart. This further contributes to the drop in blood pressure, increasing the likelihood of fainting.
Common Triggers and Contributing Factors
Vomiting’s physiological stress often combines with other factors to cause fainting. Dehydration, a common consequence of vomiting due to significant fluid loss, can lower overall blood volume. This reduced volume makes it harder for the body to maintain adequate blood pressure, increasing the likelihood of syncope. Electrolyte imbalances, often with dehydration, can disrupt nerve signaling and heart rhythm, contributing to lightheadedness and fainting.
Severe nausea can activate the vasovagal response, causing dizziness and lightheadedness. Conditions causing intense vomiting, like food poisoning or stomach flu, are common causes. Migraines, intense pain, or emotional stress can also trigger or worsen the vasovagal response during vomiting. Certain medications can also affect blood pressure or fluid balance, increasing the risk.
When to Seek Medical Help
While fainting from vomiting is often temporary, certain signs warrant immediate medical attention. Seek medical evaluation for repeated fainting episodes or if unconsciousness lasts longer than a few minutes. Any injury from falling, especially a head injury, requires medical attention.
Other warning signs include chest pain, shortness of breath, severe headache, or new confusion. Individuals with pre-existing conditions like heart disease or diabetes should seek medical advice promptly if they faint, as it could indicate a more serious underlying problem. These symptoms or conditions suggest a need for medical assessment to rule out more significant health concerns.
Managing and Preventing Episodes
To manage and prevent fainting during vomiting, several steps can be taken. If feeling lightheaded or nauseated, lie down with legs elevated to help restore blood flow to the brain. Staying hydrated is important; sip small amounts of clear fluids like water, oral rehydration solutions, or clear broths frequently, rather than large quantities at once. Oral rehydration solutions are particularly effective as they replenish lost electrolytes.
Avoid sudden movements, especially standing up quickly, to prevent a rapid drop in blood pressure. Once vomiting subsides, gradually reintroduce bland, easy-to-digest foods. To manage nausea, some find relief with ginger (e.g., tea, lozenges) or peppermint (e.g., tea, aromatherapy) due to its muscle-relaxing properties. For persistent or severe nausea, consult a doctor.