Anesthesia & Clinical Research
Open Access

Abstract

Accurate Measurement of Intraoperative Blood Loss Improves Prediction of Postoperative Hemoglobin Levels

Robert L Thurer, Jose Muniz Castro, Mazyar Javidroozi, Kimberly Burton and Nicole P Bernal

Background: Restrictive red cell transfusion is preferable to liberal transfusion in most clinical situations. However, intraoperative transfusion decisions are challenging due to uncertainty about the amount and rate of bleeding, the poor correlation of haemoglobin levels with blood loss and the effects of anesthetics on blood volume and physiologic responses. Clinicians frequently use hemoglobin levels to guide transfusion. While these "triggers" assume that the patient is normovolemic, they are often applied in situations confounded by hemodilution or hemoconcentration. We postulated that accurate measurement of surgical blood loss would facilitate prediction of postoperative hemoglobin levels, potentially leading to more accurate intraoperative transfusion decisions. Methods: Using image-processing algorithms, a novel system accurately measures blood loss by photographing surgical sponges and canisters and calculating their hemoglobin content. A formula to predict postoperative hemoglobin levels was devised and used to calculate postoperative hemoglobin levels in a study group of 167 burn and other wound excision procedures performed on 103 patients using the system. In an historical group (100 similar procedures, 60 patients) clinician estimates of blood loss were used. These predictions were compared with actual values. Results: The formula using measured blood loss in the study group was a better predictor of the actual postoperative day one hemoglobin value (R2=0.822) than was the same formula using visually estimated blood loss used in the historical group (R2=0.615). The mean absolute bias of postoperative day one hemoglobin levels in the study group was significantly lower than the mean bias in the historical group (study=group, mean 0.4, 95% CI 0.2 to 0.5 g/dL; historical group, mean 0.9, 95% CI 0.7 to 1.2 g/dL, p<0.001). Conclusion: Blood loss measurements using the novel system are a significantly better predictor of hemoglobin values obtained after surgery than traditional blood loss estimates.