Human Fist Used to Estimate Blood Loss at Trauma Scene

A new method that relies upon a person's fist could help first responders to determine correct volumes of blood loss.

Researchers at the New Jersey University of Medicine and Dentistry (UMDNJ; New Brunswick, USA) measured increments of human whole blood used to compare fist size to surface area of blood. The researchers first compared the palm side surface of the fist to spilt blood, and determined that a fist covers a surface area of blood that equals roughly 20 ml. From these measurements, a formula was created averaging blood per fist, named the MAR Method. Subsequently, two scenarios were staged using set quantities of blood, 75 ml and 750 ml; 78 study participants were then asked to estimate blood volumes both before and after being taught the MAR Method. The first estimate was based upon a visual assessment, and additional estimates were made using the MAR method. Participants got as close to the blood pool as possible and estimated the blood volume by counting how many fists it would take to cover the blood pool.

The results showed that participants had errors of 120% and 73% for visualization of the small and large pools, respectively, before learning the Mar method. However, after learning the method in a simple one-minute tutorial, the average error from the mean decreased by 76% in the smaller volume, with the interquartile range of errors decreasing by 60%. For the larger volume, the average error from the mean was reduced by 40%, and the interquartile range of errors was reduced by 45%. The study was published in the November 2009 issue of the American Journal of Emergency Medicine.

"After less than one minute of instruction, participants were able to determine blood volumes with improved accuracy and precision,” said lead author Mark Merlin, M.D., an assistant professor of emergency medicine and pediatrics at the UMDNJ. "For years, several institutions have been trying to create a simple formula for determining blood loss with a rapid, precise and accurate method. Using multiple subjects and evaluating variability between fists, this is the first successful method.”

Hypovolemia has historically been termed desanguination, meaning a massive loss of blood. It can be recognized by elevated pulse, diminished blood pressure, and the absence of perfusion as assessed by skin signs (skin turning pale) and/or capillary refill on forehead, lips, and nail beds. The patient may feel dizzy, faint, nauseated, or very thirsty. These signs are also characteristic of most types of shock. Knowing the amount of blood loss is important in assessing hypovolemia and determining appropriate emergency treatment such as infusion.

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New Jersey University of Medicine and Dentistry