General Medical Information

Erythrocyte Abnormalities

David M. Barrs

A preoperative hemoglobin should be obtained on all female patients but is not necessary in asymptomatic male patients who do not have a history of bleeding or anemia. Anemia is significant because of the decreased oxygen-carrying capacity available during anesthesia. The previous minimal acceptable hemoglobin level of 10 g/dL for surgery or transfusion has been lowered to 7 g/dL, which is adequate for tissue oxygen delivery if circulating volume is normal. Healthy patients or chronically anemic patients may undergo surgery safely at these levels if minimal blood loss is expected. In the urgent case, transfusion may be necessary to replace erythrocytes to an acceptable hemoglobin level.

Two hemoglobinopathies are of concern. The first is sickle cell disease. Sickle cell trait is not associated with increased surgical risk. In patients with the homozygous condition, the level of hemoglobin S should be reduced to about 50% by exchange transfusion to avoid sickling crisis or acute chest syndrome during anesthesia or during the postoperative period. Hypoxia, hypernatremia, and volume depletion should be avoided. The second is glucose-6-phosphate dehydrogenase deficiency, which causes oxidant damage to hemoglobin within erythrocytes and is almost exclusively seen in men. Preoperative screening for this deficiency should be performed if there is a family history of the deficiency or unexplained hemolysis. The condition is not a risk for surgery, but certain medications should be avoided in the postoperative period to minimize the risk of hemolysis.