Simultaneous Determination of Methemoglobin and Total Hemoglobin by a Continuous-flow Method1

We describe a sensitive, accurate automated method for the simultaneous measurement of methemoglobin and total hemoglobin in blood. The method can be used for either continuous in vivo monitoring or intermittent sampling at a rate of 20/h. Standardization procedures are described, in which human blood treated with sodi-um nitrite is used. Repeatability of methemoglobin and total hemoglobin measurements, expressed as coeffi-cient of variation in percent, are within ±4.1 and ±2.6%, respectively. Normal methemoglobin concen-tration’s in humans and dogs did not exceed 0.55 g/dl (3.3 % of the total hemoglobin). Additional Keyphrases: normal values #{149}dogs #{149}methe-moglobin production #{149}AutoAnalyzer #{149}in vivo monitoring cyanide poisoning The classical therapy for cyanide poisoning is to produce methemoglobin in the circulating blood. Cy-anide is rapidly detoxified as the methemoglobin rap-idly combines with it to form cyanmethemoglobin. Knowledge of the rate at which methemoglobin is produced by various compounds in vivo could be use-ful as an index of the therapeutic value of the com-pounds. It was for this purpose that we developed the method presented in this report. Many papers deal with the manual spectrophotometric measurement of normal and abnormal blood pigments (1-6). Al-though automated methods for hemoglobin are avail-able (7-9), none has been reported for methemogbo-bin. The mechanized method described here can be used to measure methemoglobin and total hemoglo-bin concentrations simultaneously. The circulating blood can be monitored continuously through an in-travenous or intra-arterial catheter (in vivo sampler