What are the primary causes of sickle cell crisis?

Sickle cell crisis, also known as vaso-occlusive crisis, primarily results from conditions that lead to sickling of the red blood cells. These conditions include hypoxia and dehydration.

Hypoxia, a deficiency of oxygen in the tissues, can trigger sickling because it lowers the amount of oxygen available for the red blood cells to maintain their normal, biconcave shape. When oxygen levels drop, the red blood cells become rigid and sticky, leading to blockage of blood flow in small vessels, which results in pain and potential organ damage.

Dehydration exacerbates this situation as it increases the viscosity of blood, making it thicker and more prone to blockage. When red blood cells are less hydrated, they lose their flexibility, further increasing the likelihood of sickling and vaso-occlusive events.

While other choices mention factors like infection and stress, which can contribute to a crisis indirectly, they are not the primary physiological causes. The critical factors leading directly to a sickle cell crisis are the combination of reduced oxygen supply and decreased hydration.