Assessing gravimetric estimation of intraoperative blood loss

Our objective was to assess the accuracy of gravimetric estimation of intraoperative blood loss using the colorimetric method. Forty laparotomy sponges were selected randomly from general gynecology cases during a 2 month period. The blood contained on each sponge had been assessed by the OR staff by weighing the sponges. The hemoglobin contained in the sponges was then converted to alkali hematin and measured in a Beckman spectrophotometer at 465 nm. Using the patient's preoperative hemoglobin measurement, the amount of blood present in the sponges was determined. The gravimetric and colorimetric measurements were compared statistically. We found no statistically significant correlation between the amount of blood loss estimated by the gravimetric method and the actual blood loss as measured by the colorimetric method (P = 0.074). The gravimetric method of assessing intraoperative blood loss is neither precise nor accurate.