How does blood loss relate to the extent of surgical wound excision?

We investigated a novel system that uses image-processing algorithms to accurately measure the hemoglobin content of discarded surgical sponges to determine how blood loss relates to the excised area when current methods to minimize bleeding are employed. The system was used during 130 procedures in adult patients having wound excisions  ≥1% BSA (study group). An historic group of 105 similar cases in whom visually estimated blood was determined was also evaluated.

Surgical blood loss was less than previous estimates. The correlation between blood loss and the excised area in the study group was poor (R²=0.3988 for all patients and R²=0.1439 for excisions  ≥10% BSA). Moreover, the visual estimates of blood loss in the historic group were more closely related to excised area than the accurate measurements in the study group (R²=0.6017 (historic), R²=0.3988 (study), p<0.001 for both). The mean absolute unstandardized residuals were 140.18±158.52 (historic) vs. 307.99±317.03 (study), p<0.001.

As demonstrated in the historic group, visual estimates of blood loss tend to be more related to the size of excision than the amount of bleeding. The actual blood loss is not well correlated with the extent of excision. Clinicians should not rely on traditional blood loss estimates. Accurate measurement is needed to inform transfusion decisions and guide care.