A new nomogram facilitating adequate haemodilution

When using deliberate haemodilution to a certain haematocrit value (Hct), the appropriate preoperative blood volume of the patient must be determined and matched with the transfusion volume at a certain blood loss. In order to facilitate such calculations a nomogram was constructed, aiming for a final Hct of 33%. Preoperative Hct, height, weight and sex of the patient are input variables. After drawing three straight lines, the nomogram yields the normal blood volume and the acceptable pre-transfusion blood loss (BL). This nomogram was used during surgery when the preoperative Hct exceeded 35%. Protocols from 100 patients bleeding more than 50% of their BL were studied. Blood loss was 1.1 +/- 0.6 1 (mean +/- s.d.) ranging from 0.4 to 4.0 1. Fifty-one of the patients received blood transfusion. This program resulted in a decrease of Hct (mean +/- s.d.) from 41 +/- 3% preoperatively to 33 +/- 4% during the first 30 min postoperatively. Sixty-three of the patients had a final Hct of 30-35%, 13 had 27-29% and one had 26%. The low values were most likely due to underestimation and consequent unsubstituted blood loss. In summary, the nomogram makes time-consuming mathematical operations unnecessary. It was easy to use and the postoperative Hct was close to that desired in most patients.