CARBOXYHEMOGLOBIN LEVELS AS AN INDEX OF HEMOLYSIS

Abstract

Carbon monoxide (CO) and bilirubin are formed in equimolar amounts during the catabolism of heme. In demonstrating increased endogenous CO formation from accelerated hemolysis it is important to separate out the effect of variable exogenous CO exposure. The carboxyhemoglobin level in 229 normal children ranged from 0.6 to 3.9% saturation, with a mean of 1.30% (S.D. = 0.47%). Forty children with hemolytic diseases had from 0.8 to 4.0% of their circulating hemoglobin saturated with CO with a mean of 1.95% (S.D. = 0.88%). The sixfold range observed in normal children is largely due to variable ambient CO exposure, since 574 comparisons between nonsmoking adults who were breathing the same gas mixture for over 18 hours, always gave carboxyhemoglobin values which differed by less than 0.35% saturation. By comparing the blood CO content of a suspect hemolytic patient with a normal sibling or another control individual who has been exposed to the same exogenous CO level for several hours, it is possible to obtain a qualitative index of increased endogenous CO formation. Thirty-seven children with known hemolytic disease always had carboxyhemoglobin levels which were higher than their matched environmental controls.