A formula to calculate blood cross-match requirements for early burn surgery in children.

Excessive bleeding from the burn site accompanies burn surgery, and blood transfusions are therefore an essential and expensive ingredient. A formula, based on the total surface area to be involved in surgery (i.e. burn plus donor area) and the patient's total blood volume, has been in use in our hospital for calculating blood cross-match volumes, but has not been scientifically evaluated. Prospectively the predicted blood loss, based on the formula in 111 consecutive paediatric burns undergoing surgery, was compared with the actual blood loss as measured using a gravimetric method. Provided that an accurate surface area to be involved in surgery is interposed into the formula, there was a statistically highly significant correlation between the predicted and actual blood loss. Invoking this simple formula may help in decreasing unnecessary cross-matching, and discarding, of blood products.