What could cause a sickle cell crisis?

• A. dehydration during illness
• B. cold weather
• C. certain medications, high altitudes, and strenuous exercise
• D. drinking plenty of water

Answer: (C)

Sickle cell crisis occurs when red blood cells containing hemoglobin S become deoxygenated and take on a rigid, sickle shape, which can block small blood vessels and cause pain and tissue ischemia. Factors that lower oxygen delivery or increase blood viscosity can precipitate this process. Certain medications that promote vasoconstriction or dehydration, high altitudes with reduced oxygen, and strenuous exercise that raises oxygen demand and can lead to temporary hypoxemia collectively create conditions that encourage sickling and vaso-occlusion. Drinking plenty of water helps prevent dehydration, so it would not trigger a crisis; other triggers like cold weather can also contribute, but the listed combination captures well-known precipitating factors for a vaso-occlusive event.