H Sickle cell disease
Pathophysiology
Sickle cell is a disorder transmitted as an autosomal recessive trait that causes an abnormality of the globin genes in hemoglobin. A person who is homozygous for hemoglobin S manifests the disorder. Individuals may have the sickle cell trait or sickle cell disease. The sickle cell trait is a heterozygous disorder seen in 10% of African Americans. Their hemoglobin S levels are normally 30% to 50%, and sickling is seen with a Po2 of 20 to 30 mmHg. Sickle cell disease is a homozygous disorder seen in 0.5% to 1.0% of African Americans. The majority of the hemoglobin molecule is hemoglobin S, and sickling is seen with a Po2 of 30 to 40 mmHg. A crisis may be caused by a decrease of oxygen saturation and temperature, infections, dehydration, stasis, or acidosis. These complicated scenarios translate into perioperative mortality rates of 10% and postoperative complications of 50%.