MT refers to a situation where a patient receives 5 or more units of pRBCs in 4 hours or 10 or more units of pRBCs in 24 hours. Nevertheless, this definition is considered arbitrary without clear-cut clinical implications; furthermore, it fails to identify those at an increased risk for hemorrhagic death. In contrast, the critical administration threshold (CAT) definition of 3 or more units in 1 hour has a stronger association with mortality compared to MT; it can serve as an activation trigger for initiating an MTP, a system created to facilitate rapid administration of large-volume transfusions to patients in hemorrhagic shock.

The ABC score is a validated, nonlaboratory scoring system, designed to identify patients who will require MTP. It looks at four parameters: (1) penetrating mechanism, (2) positive FAST, (3) arrival SBP less than or equal to 90 mm Hg, and (4) arrival HR greater than or equal to 120. A score of 2 (positive cutoff) or greater was 75% sensitive and 86% specific for predicting MT. Shock index (SI) is another scoring system; it is calculated as initial HR divided by initial SBP. An SI greater than or equal to 0.8 to 1 is often used as the cutoff to predict the need for MTP. Schroll et al found that SI was a more sensitive predictor of MTP and required less skill to calculate.

References

• Nunez TC, Voskresensky IV, Dossett LA, et al. Early prediction of massive transfusion in trauma: simple as ABC (assessment of blood consumption)? J Trauma. 2009;66:346-352.
• Savage SA, Zarzaur BL, Croce MA, et al. Redefining massive transfusion when every second counts. J Trauma Acute Care Surg. 2013;74:396-402.
• Schroll R, Swift D, Tatum D, et al. Accuracy of shock index versus ABC score to predict need for massive transfusion in trauma patients. Injury. 2018;49:15-19.