### Description

McLaughlin et al identified risk factors associated with massive blood transfusion to a combat casualty. The authors are from the U.S. Institute for Surgical Research at Fort Sam Houston, Texas, and Walter Reed Army Medical Center.

Massive blood transfusion is defined as transfusion of >= 10 units of bleed during the first 24 hours after trauma center admission.

Parameters:

(1) heart rate in beats per minute

(2) systolic blood pressure in mm Hg

(3) pH of arterial blood

(4) hematocrit in percent

 Parameter Finding Points heart rate <= 105 beats per minute 0 > 105 beats per minute 1 systolic blood pressure >= 110 mm Hg 0 < 110 mm Hg 1 pH of arterial blood >= 7.25 0 < 7.25 1 hematocrit >= 32 percent 0 < 32 percent 1

total number of risk factors for massive blood transfusion =

= SUM(points for the 4 parameters)

X =

= (0.825 * (points for systolic blood pressure)) + (0.826 * (points for heart rate)) + (1.044 * (points for hematocrit)) + (0.462 * (points for pH)) - 1.576

probability of massive blood transfusion =

= 1 / (1 + EXP((-1) * X))

Interpretation:

• minimum number of risk factors: 0

• maximum number of risk factors: 4

• The more risk factors present the more likely that the patient will receive massive blood transfusion.

 Number of Risk Factors Percent with Massive Transfusion 0 12% 1 22% 2 43% 3 62% 4 82%

Performance for probability equation:

• The sensitivity is 59% and specificity 77%.

• The positive predictive value is 66% and negative predictive value 72%.