Influence of Measurement Principle on Total Hemoglobin Value

Abstract Background: Total hemoglobin measurement is indispensable for determining the stroke type (haemorrhagic vs. ischaemic) and need for blood transfusion. Conductivity- and absorbance-based measurement methods are used for blood gas analysis of total hemoglobin. For conductivity-based measurement, total hemoglobin is calculated after converting blood conductivity into a hematocrit value, whereas absorbance measurement is based on light absorbance after red blood cell hemolysis. We previously reported hemolysis observed after infusion or transfusion during veno-arterial extracorporeal membrane oxygenation, and total hemoglobin differed between conductivity and absorbance measurement methods possibly due to plasma electrolyte changes and hemolysis. Methods: In this study, test samples with controlled electrolyte changes and hemolysis were created by adding sodium chloride, distilled water or hemolysed blood to blood samples collected from healthy volunteers, and total hemoglobin values were compared between both methods. Results: Conductivity-based measurement revealed reduced total hemoglobin value (from 15.49 to 13.05 g/dl) following the addition of 10% sodium chloride, which was also reduced by the addition of hemolysate. Conversely, the addition of distilled water significantly increased total hemoglobin value than the expected value. In the absorbance method, there was no significant change in total hemoglobin value due to electrolyte change or hemolysis. Conclusions: The absorbance method should be used when measuring total hemoglobin in patients with expected blood conductivity changes. However, when using this method, the added contribution of hemoglobin from hemolysed erythrocytes lacking oxygen carrying capacity must be considered.