title: The new metric to define large-volume hemorrhage: results of a prospective study of the critical administration threshold.
abstract: BACKGROUND
  Definitions of massive transfusion (MT), 10 or more units of packed red blood cells (PRBCs) in 24 hours, focus on static volumes over fixed times. This arbitrary volume definition promotes survivor bias and fails to identify the "massively" transfused patient. In previous work, the critical administration threshold (CAT) was created to incorporate both rate and volume of transfusion. CAT proved a superior predictor of mortality compared with traditional MT. The purpose of this study was to prospectively validate CAT in a larger trauma population.
  
  
  METHODS
  Patients receiving at least 1 U of PRBCs within the first day of admission were identified prospectively. Administration time of each unit of PRBCs was recorded in minutes. CAT status, defined as receipt of at least 3 U of blood in a 60-minute period, was identified for the first 24 hours. CAT+ patients were quantified by the number of times CAT+ was reached, that is, once (CAT1), twice (CAT2), three times (CAT3), or 4 or more times (CAT4). A multivariable Cox proportional hazard model with a time-varying covariate was used to quantify a patient's risk of death with increasing CAT status.
  
  
  RESULTS
  A total of 316 met inclusion criteria, 161 of whom were CAT+. Seventy-six percent were male, mean age was 38 years, and median Injury Severity Score (ISS) was 15. CAT+ was associated with a twofold increased risk of death (hazard ratio, 1.809; 95% confidence interval, 1.020-3.209). Ninety-one patients were CAT+ and received less than 10 U of blood, thereby MT- (CAT+/MT-). CAT+/MT- had significant injury patterns, with a median ISS of 14, 43% penetrating injury, and 10% mortality.
  
  
  CONCLUSIONS
  CAT allows early identification of injured patients at greatest risk of death. Encompassing both rate and volume of transfusion, CAT is a tool more sensitive than common MT definitions. Studies examining large-volume blood transfusions should use CAT to identify patients, to accurately identify cohorts of interest.
  
  
  METHODS
  Diagnostic tests, level II.
authors.affiliation: From the University of Tennessee Health Sciences Center (S.A.S., J.J.S., W.P.D., M.A.C., T.C.F.), Memphis, Tennessee; and Indiana University-Purdue University, Indianapolis (B.L.Z.), Indianapolis, Indiana.
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Savage
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Sumislawski
authors.forename: Ben L
authors.initials: BL
authors.lastname: Zarzaur
authors.forename: Wesley P
authors.initials: WP
authors.lastname: Dutton
authors.forename: Martin A
authors.initials: MA
authors.lastname: Croce
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Fabian
mesh_terms: D000328:Adult; D001803:Blood Transfusion / Q000379:methods*; D005260:Female; D006470:Hemorrhage / Q000401:mortality / Q000628:therapy*; D017052:Hospital Mortality; D006801:Humans; D015601:Injury Severity Score; D008297:Male; D010043:Outcome and Process Assessment, Health Care; D011446:Prospective Studies; D012307:Risk Factors; D013714:Tennessee / Q000453:epidemiology