title: Predicting blood transfusion using automated analysis of pulse oximetry signals and laboratory values.
abstract: BACKGROUND
  Identification of hemorrhaging trauma patients and prediction of blood transfusion needs in near real time will expedite care of the critically injured. We hypothesized that automated analysis of pulse oximetry signals in combination with laboratory values and vital signs obtained at the time of triage would predict the need for blood transfusion with accuracy greater than that of triage vital signs or pulse oximetry analysis alone.
  
  
  METHODS
  Continuous pulse oximetry signals were recorded for directly admitted trauma patients with abnormal prehospital shock index (heart rate [HR] / systolic blood pressure) of 0.62 or greater. Predictions of blood transfusion within 24 hours were compared using Delong's method for area under the receiver operating characteristic (AUROC) curves to determine the optimal combination of triage vital signs (prehospital HR + systolic blood pressure), pulse oximetry features (40 waveform features, O2 saturation, HR), and laboratory values (hematocrit, electrolytes, bicarbonate, prothrombin time, international normalization ratio, lactate) in multivariate logistic regression models.
  
  
  RESULTS
  We enrolled 1,191 patients; 339 were excluded because of incomplete data; 40 received blood within 3 hours; and 14 received massive transfusion. Triage vital signs predicted need for transfusion within 3 hours (AUROC, 0.59) and massive transfusion (AUROC, 0.70). Pulse oximetry for 15 minutes predicted transfusion more accurately than triage vital signs for both time frames (3-hour AUROC, 0.74; p = 0.004) (massive transfusion AUROC, 0.88; p < 0.001). An algorithm including triage vital signs, pulse oximetry features, and laboratory values improved accuracy of transfusion prediction (3-hour AUROC, 0.84; p < 0.001) (massive transfusion AUROC, 0.91; p < 0.001).
  
  
  CONCLUSIONS
  Automated analysis of triage vital signs, 15 minutes of pulse oximetry signals, and laboratory values predicted use of blood transfusion during trauma resuscitation more accurately than triage vital signs or pulse oximetry analysis alone. Results suggest automated calculations from a noninvasive vital sign monitor interfaced with a point-of-care laboratory device may support clinical decisions by recognizing patients with hemorrhage sufficient to need transfusion.
  
  
  METHODS
  Epidemiologic/prognostic study, level III.
authors.affiliation: From the USAF Center for Sustainment of Trauma and Readiness Skills (S.S., C.Mi., L.H., R.F.); Shock Trauma Anesthesiology Research Center and Charles McMathias National Study Center for Trauma and EMS (P.H., A.A., Y.W., C.Ma.); and Department of Anesthesiology (S.Y., S.G.), University of Maryland School of Medicine, Baltimore, Maryland.
authors.forename: Stacy
authors.initials: S
authors.lastname: Shackelford
authors.forename: Shiming
authors.initials: S
authors.lastname: Yang
authors.forename: Peter
authors.initials: P
authors.lastname: Hu
authors.forename: Catriona
authors.initials: C
authors.lastname: Miller
authors.forename: Amechi
authors.initials: A
authors.lastname: Anazodo
authors.forename: Samuel
authors.initials: S
authors.lastname: Galvagno
authors.forename: Yulei
authors.initials: Y
authors.lastname: Wang
authors.forename: Lauren
authors.initials: L
authors.lastname: Hartsky
authors.forename: Raymond
authors.initials: R
authors.lastname: Fang
authors.forename: Colin
authors.initials: C
authors.lastname: Mackenzie
mesh_terms: D000328:Adult; D001803:Blood Transfusion / Q000706:statistics & numerical data*; D005260:Female; D006403:Hematologic Tests; D006801:Humans; D010092:Oximetry; D011237:Predictive Value of Tests; D014218:Triage; D055986:Vital Signs; D014947:Wounds and Injuries / Q000628:therapy*