Cardiopulmonary bypass in hereditary spherocytosis: a case report.

Hereditary spherocytosis is a genetically determined abnormality of red blood cells. It is likely that a defect of intracellular glycolysis results in the formation of spherical cells (spherocytes) which have a reduced life span and exhibit increased osmotic fragility in hypotonic saline solutions, increased susceptibility to mechanical trauma, and spontaneous lysis on incubation. Lysis is markedly reduced by the presence of added glucose (Dacie, 1963). Splenectomy usually results in clinical cure, although haematological signs of the disease may persist; for example, while osmotic fragility improves, it rarely returns to normal, and mechanical fragility of both fresh and incubated blood remains significantly abnormal. The imposition of cardiopulmonary bypass on normal subjects is associated with some destruction of the formed elements of blood. Haemolysis occurs, and plasma haemoglobin levels rise at a rate which is seldom less than 0-25 mg per minute, consequent upon the trauma of bubble oxygenation, roller pumps and cardiotomy suction. Haemolysis of this degree is seldom important as the kidney is well able to tolerate plasma haemoglobin levels of up to 250 mg per 100 ml, and oxygen carrying capacity is not seriously deranged. However, the altered robustness of the red cells in a patient with hereditary spherocytosis may preclude an operation with cardiopulmonary bypass on the ground of excessive haemolysis. There are no available published reports of an operation with cardiopulmonary bypass in a patient with hereditary spherocytosis. We report a reconstructive operation on the mitral valve in such a patient, with particular reference to the conduct of cardiopulmonary bypass.