Which of the following is a risk factor for heat syncope?

Which of the following is a risk factor for heat syncope?

• A. Regular hydration
• B. Dehydration
• C. Adequate venous return
• D. High cardiovascular fitness

Answer: (B)

Heat syncope happens when heat causes peripheral blood vessels to dilate and blood pools in the skin, dropping the amount of blood returning to the heart and reducing blood flow to the brain. Dehydration lowers plasma volume, which further decreases venous return and cardiac output, making fainting more likely, especially after standing for a while or changing posture in hot conditions. Keeping well-hydrated helps maintain circulating blood volume and blood pressure in heat, protecting against this, while adequate venous return and good cardiovascular fitness also support stability in hot environments rather than increasing risk.

Heat syncope happens when heat causes peripheral blood vessels to dilate and blood pools in the skin, dropping the amount of blood returning to the heart and reducing blood flow to the brain. Dehydration lowers plasma volume, which further decreases venous return and cardiac output, making fainting more likely, especially after standing for a while or changing posture in hot conditions. Keeping well-hydrated helps maintain circulating blood volume and blood pressure in heat, protecting against this, while adequate venous return and good cardiovascular fitness also support stability in hot environments rather than increasing risk.