title: Recursive partitioning identifies greater than 4 U of packed red blood cells per hour as an improved massive transfusion definition.
abstract: BACKGROUND
  Massive transfusion (MT) is classically defined as greater than 10 U of packed red blood cells (PRBCs) in 24 hours. This fails to capture the most severely injured patients. Extending the previous work of Savage and Rahbar, a rolling hourly rate-based definition of MT may more accurately define critically injured patients requiring early, aggressive resuscitation.
  
  
  METHODS
  The Prospective Observational Multicenter Major Trauma Transfusion (PROMMTT) trial collected data from 10 Level 1 trauma centers. Patients were placed into rate-based transfusion groups by maximal number of PRBCs transfused in any hour within the first 6 hours. A nonparametric analysis using classification trees partitioned data according to mortality at 24 hours using a predictor variable of maximum number PRBC units transfused in an hour. Dichotomous variables significant in previous scores and models as predictors of MT were used to identify critically ill patients: a positive finding on Focused Assessment with Sonography in Trauma (FAST) examination, Glasgow Coma Scale (GCS) score less than 8, heart rate greater than 120 beats/min, systolic blood pressure less than 90 mm Hg, penetrating mechanism of injury, international normalized ratio greater than 1.5, hemoglobin less than 11, and base deficit greater than 5. These critical indicators were then compared among the nodes of the classification tree. Patients omitted included those who did not receive PRBCs (n = 24) and those who did not have all eight critical indicators reported (n = 449).
  
  
  RESULTS
  In a population of 1,245 patients, the classification tree included 772 patients. Analysis by recursive partitioning showed increased mortality among patients receiving greater than 13 U/h (73.9%, p < 0.01). In those patients receiving less than or equal to 13 U/h, mortality was greater in patients who received more than 4 U/h (16.7% vs. 6.0%, p < 0.01) (Fig. 1). Nodal analysis showed that the median number of critical indicators for each node was 3 (2-4) (≤4 U/h), 4 (3-5) (>4 U/h and ≤13 U/h), and 5 (4-5.5) (>13 U/h).
  
  
  CONCLUSIONS
  A rate-based transfusion definition identifies a difference in mortality in patients who receive greater than 4 U/h of PRBCs. Redefining MT to greater than 4 U/h allows early identification of patients with a significant mortality risk who may be missed by the current definition.
  
  
  METHODS
  Prognostic/epidemiologic study, level III.
authors.affiliation: From the Division of Trauma, Critical Care and Acute Care Surgery (A.M.M., D.H., B.D., L.K., K.J.B., M.A.S.), School of Medicine, Oregon Health & Science University, Portland, Oregon; Center for Translational Injury Research (E.E.F., J.B.H.), Division of Acute Care Surgery, Department of Surgery, Medical School, University of Texas Health Science Center, Houston, Texas; Biostatistics/Epidemiology/Research Design Core (M.H.R.), Center for Clinical and Translational Sciences, University of Texas Health Science Center, Houston, Texas; Division of General Surgery (M.J.C.), Department of Surgery, School of Medicine, University of California San Francisco, San Francisco, California; Division of Trauma and Critical Care (E.M.B.), Department of Surgery, School of Medicine, University of Washington, Seattle, Washington.
authors.forename: Alexis Marika
authors.initials: AM
authors.lastname: Moren
authors.forename: David
authors.initials: D
authors.lastname: Hamptom
authors.forename: Brian
authors.initials: B
authors.lastname: Diggs
authors.forename: Laszlo
authors.initials: L
authors.lastname: Kiraly
authors.forename: Erin E
authors.initials: EE
authors.lastname: Fox
authors.forename: John B
authors.initials: JB
authors.lastname: Holcomb
authors.forename: Mohammad Hossein
authors.initials: MH
authors.lastname: Rahbar
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Brasel
authors.forename: Mitchell Jay
authors.initials: MJ
authors.lastname: Cohen
authors.forename: Eileen M
authors.initials: EM
authors.lastname: Bulger
authors.forename: Martin A
authors.initials: MA
authors.lastname: Schreiber
mesh_terms: D015415:Biomarkers / Q000032:analysis; D017707:Erythrocyte Transfusion; D006470:Hemorrhage / Q000401:mortality / Q000628:therapy*; D006801:Humans; D011446:Prospective Studies; D012151:Resuscitation / Q000379:methods*; D015599:Trauma Severity Indices; D014947:Wounds and Injuries / Q000401:mortality / Q000628:therapy*
chemical_list: D015415:Biomarkers