Redefining massive transfusion when every second counts.

BACKGROUND: The massive transfusion (MT) concept (>10-U packed red blood cells per 24 hours) is retrospective, arbitrary, and prone to survivor bias. Accounting for rate and timing is a more accurate conceptual framework. We redefined MT as a critical administration threshold (CAT) of 3 U/h, which is clinically pertinent and reflects hemorrhagic shock. The purpose of this study was to compare the traditional form of MT to a CAT definition in predicting mortality.
METHODS: Patients receiving transfusion in the first 24 hours were included. Precise transfusion times for each unit, in minutes, were calculated from time of injury. MT and CAT were compared to determine risk of death. Univariate and multivariate analyses were used to examine inpatient mortality.
RESULTS: A total of 169 patients(70%, >10 New Injury Severity Score [NISS]) were studied; 46% were CAT+; 22% met the MT criteria. With logistic regression, a CAT of 3 U/h (CAT+) was more predictive of death compared with 2, 4, 5, or 6 U/h. CAT was met once (CAT 1), twice (CAT 2) or more than 3 times (CAT 3) in 21%, 14%, and 11%, respectively. Increasing CAT was associated with increased mortality. CAT identified 75% of all deaths; MT only identified 33% and failed to identify 42% of CAT+ deaths. CAT (relative risk [RR] 3.58; 95% confidence interval [CI] 1.80-7.15) had a stronger association with mortality compared with MT(RR, 1.82; 95% confidence interval, 1.02-3.26).
CONCLUSION: The traditional definition of MT is inadequate to reflect illness severity. Using CATs allows prospective identification of critically ill trauma patients and eliminates survivor bias. CAT may serve as an activation trigger for transfusion protocols, allowing early identification of patients with critical transfusion requirements. Clinical trials involving transfusion strategies should consider CAT as an instrument for evaluating outcomes. LEVEL OF EVIDENCE: Diagnostic/prognostic study, level II.