Which statement best describes precipitants of a vaso-occlusive crisis in sickle cell disease?

Which statement best describes precipitants of a vaso-occlusive crisis in sickle cell disease?

• A. High oxygen tension, adequate hydration, normal pH
• B. Hypercapnia with dehydration
• C. Iron overload
• D. Low oxygen tension, dehydration, acidosis, and infection

Answer: (D)

Vaso-occlusive crises occur when conditions push hemoglobin S toward deoxygenation and promote red blood cell sickling. Low oxygen tension means tissues aren’t well oxygenated, driving HbS to polymerize and the cells to sickle. Dehydration thickens the blood and raises viscosity, slowing flow and encouraging sickled cells to jam in small vessels. Acidosis shifts the balance toward more deoxygenated HbS, increasing the tendency to sickle. Infections add inflammation, fever, and metabolic stress, which worsen hypoxia and dehydration and trigger crisis events. Together, these factors create a milieu that readily promotes vaso-occlusion. By contrast, high oxygen tension, adequate hydration, and normal pH lessen sickling, so they are not precipitants. Iron overload is a long-term transfusion complication, not an acute trigger for a crisis.

Vaso-occlusive crises occur when conditions push hemoglobin S toward deoxygenation and promote red blood cell sickling. Low oxygen tension means tissues aren’t well oxygenated, driving HbS to polymerize and the cells to sickle. Dehydration thickens the blood and raises viscosity, slowing flow and encouraging sickled cells to jam in small vessels. Acidosis shifts the balance toward more deoxygenated HbS, increasing the tendency to sickle. Infections add inflammation, fever, and metabolic stress, which worsen hypoxia and dehydration and trigger crisis events. Together, these factors create a milieu that readily promotes vaso-occlusion. By contrast, high oxygen tension, adequate hydration, and normal pH lessen sickling, so they are not precipitants. Iron overload is a long-term transfusion complication, not an acute trigger for a crisis.