The Effect of Heparin Dilution on Hemoglobin Measurement from Arterial Blood Samples

We present data to demonstrate that hemoglobin values obtained from heparinized arterial blood are wrong. We found that the error in hemoglobin values obtained from heparin-diluted blood is inversely proportional to the volume of blood drawn and directly proportional to the syringe dead-space volume. We also found that certain needle sizes do not affect the error. We determined the volume of dead space in various syringe sizes and found the volume to be constant for a given syringe size. Therefore, if the dead space volume of any syringe size is accurately measured, a factor can be calculated that corrects the hemoglobin value obtained from the diluted blood sample to the true value for an undiluted sample.