New method to improve accuracy of estimated blood loss

Dec 16 2009

Determining blood loss at the scene of trauma can be critical to successful patient treatment. Health care workers such as emergency medical technicians have used visual estimation, which can be highly inaccurate, as their only means of determining volumes of blood loss. A new, simple method developed by UMDNJ-Robert Wood Johnson Medical School may drastically improve their accuracy.

A team led by Dr. Mark Merlin, an assistant professor of emergency medicine and pediatrics at the UMDNJ-Robert Wood Johnson Medical School and medical director of emergency medical services at Robert Wood Johnson University Hospital, has developed the MAR Method, which relies upon a person's fist to determine external blood loss.

In a clinical trial designed by Merlin, increments of human whole blood were measured. The researchers compared the anterior (palm side) surface of the fist to the surface area of blood present and created a formula averaging blood per fist. They determined that a fist covers a surface area of blood that equals roughly 20 mL.

Then two scenarios were staged using 75 and 750 mL of blood. Seventy-eight study participants were asked to estimate blood volumes before and after being taught the MAR Method. The first estimate was based upon a visual assessment. Additional estimates were made using the MAR Method. Participants got as close to the blood pool as possible and estimate the blood volume by counting how many fists it would take to cover the blood pool.

"After less than one minute of instruction, participants were able to determine blood volumes with improved accuracy and precision," the researchers report in an article entitled "External blood loss estimation using the MAR Method." The article recently appeared in the American Journal of Emergency Medicine.

"For years, several institutions have been trying to create a simple formula for determining blood loss with a rapid, precise and accurate method," Merlin said. "Using multiple subjects and evaluating variability between fists, this is the first successful method."

Source: University of Medicine and Dentistry of New Jersey