Proper estimation of blood loss on scene of trauma: tool or tale?

Background: Visually estimated amount of blood loss may influence decision making in the prehospital setting. The purpose of this study was to determine the ability and accuracy of paramedics and emergency physicians to visually estimate a volume of external blood loss and the influence of different vital signs.

Methods: In a prospective, blinded, observational design, participants were asked to visually estimate the amount of blood in six simulated trauma scenarios. Casualties were provided with a simulated injury, and a certain amount of artificial blood that was poured on the casualties' clothing and on the floor. In addition, vital signs (i.e., blood pressure and heart rate) were given. Each two moulage patients were provided with the same injury pattern and the same simulated blood loss. Although one patient seemed to be normovolemic, the other seemed to be hypovolemeic by the given vital signs.

Results: With regard to all given amounts of blood loss, providing vital parameters suggesting instability (i.e., low blood pressure, high heart rate) led to a higher estimation of the lost blood volume in both paramedics and emergency physicians. However, estimations were influenced impressively by the given parameters. For both stable and unstable patients, small actual volumes were overestimated, whereas higher volumes tended to be underestimated. Neither occupational status (emergency physician or paramedic) nor gender or level of experience influenced accuracy of estimated blood loss significantly.