Real-time heart rate entropy predicts the need for lifesaving interventions in trauma activation patients.
BACKGROUND
Heart rate complexity (HRC), commonly described as a "new vital sign," has shown promise in predicting injury severity, but its use in clinical practice has been precluded by the absence of real-time data. This study was conducted to evaluate the utility of real-time, automated, instantaneous, hand-held heart rate entropy analysis in predicting the need for lifesaving interventions (LSIs). We hypothesized that real-time HRC would predict LSIs.


METHODS
Prospective enrollment of patients who met criteria for trauma team activation was conducted at a Level I trauma center (September 2011 to February 2012). A novel, hand-held, portable device was used to measure HRC (by sample entropy) and time-domain heart rate variability continuously in real time for 2 hours after the moment of presentation. Electric impedance cardiography was used to determine cardiac output. Patients who received an LSI were compared with patients without any intervention (non-LSI). Multivariable analysis was performed to control for differences between the groups.


RESULTS
Of 82 patients enrolled, 21 (26%) received 67 LSIs within 24 hours of hospital arrival. Initial systolic blood pressure was similar in both groups. LSI patients had a lower Glasgow Coma Scale (GCS) score (9.2 [5.1] vs. 14.9 [0.2], p < 0.0001). The mean (SD) HRC value on presentation was 0.8 (0.6) in the LSI group compared with 1.5 (0.6) in the non-LSI group (p < 0.0001). With the use of logistic regression, initial HRC was the only significant predictor of LSI. A cutoff value for HRC of 1.1 yields sensitivity, specificity, negative predictive value, and positive predictive value of 86%, 74%, 94%, and 53%, respectively, with an accuracy of 77% for predicting an LSI.


CONCLUSIONS
Decreased HRC on hospital arrival is an independent predictor of the need for LSI in trauma activation patients. Real-time HRC may be a useful adjunct to standard vital signs monitoring and predicts LSIs.


METHODS
Prognostic and diagnostic study, level III.
From the Division of Trauma, Emergency Surgery, and Surgical Critical Care, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts.
Ali Y
AY
Mejaddam
Oscar A
OA
Birkhan
Antonis C
AC
Sideris
Gwendolyn M
GM
Van der Wilden
Ayesha M
AM
Imam
John O
JO
Hwabejire
Yuchiao
Y
Chang
George C
GC
Velmahos
Peter J
PJ
Fagenholz
Daniel D
DD
Yeh
Marc A
MA
de Moya
David Richard
DR
King
D000328:Adult; D022561:Advanced Cardiac Life Support; D002302:Cardiac Output / Q000502:physiology; D005260:Female; D015600:Glasgow Coma Scale; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D015601:Injury Severity Score; D016015:Logistic Models; D008297:Male; D015999:Multivariate Analysis; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D014947:Wounds and Injuries / Q000503:physiopathology* / Q000628:therapy