Elsevier

Journal of Critical Care

Volume 28, Issue 6, December 2013, Pages 1109.e1-1109.e4
Journal of Critical Care

Electronic Article
Real-time sample entropy predicts life-saving interventions after the Boston Marathon bombing

https://doi.org/10.1016/j.jcrc.2013.08.026Get rights and content

Abstract

Purpose

Identifying patients in need of a life-saving intervention (LSI) during a mass casualty event is a priority. We hypothesized that real-time, instantaneous sample entropy (SampEn) could predict the need for LSI in the Boston Marathon bombing victims.

Materials and methods

Severely injured Boston Marathon bombing victims (n = 10) had sample entropy (SampEn) recorded upon presentation using a continuous 200-beat rolling average in real time. Treating clinicians were blinded to real-time results. The correlation between SampEn, injury severity, number, and type of LSI was examined.

Results

Victims were males (60%) with a mean age of 39.1 years. Injuries involved lower extremities (50.0%), head and neck (24.2%), or upper extremities (9.7%). Sample entropy negatively correlated with Injury Severity Score (r = − 0.70; P = .023), number of injuries (r = − 0.70; P = .026), and the number and need for LSI (r = − 0.82; P = .004). Sample entropy was reduced under a variety of conditions.

Empty CellSampEn (mean ± SD)P
Amputation, n = 50.7 ± 0.3
No amputation, n = 51.9 ± 0.8.027
Transfusion, n = 50.7 ± 0.3
No transfusion, n = 51.9 ± 0.8.027
Intubation, n = 60.8 ± 0.3
No intubation, n = 42.1 ± 0.7.027
Vasopressors, n = 70.8 ± 0.3
No vasopressors, n = 32.4 ± 0.3.004

Conclusions

Sample entropy strongly correlates with injury severity and predicts LSI after blast injuries sustained in the Boston Marathon bombings. Sample entropy may be a useful triage tool after blast injury.

Section snippets

Background

Appropriate triage of patients after traumatic injury remains a challenge, especially during mass casualty events, such as the Boston Marathon bombing on April 15, 2013. Despite the large number of victims, not all would be severely injured or require life-saving interventions (LSI). Traditional vital signs may not become altered until compensatory physiologic mechanisms become completely exhausted [1]. Various measures of heart rate variability (HRV) and complexity have been shown to be

Methods

The Massachusetts General Hospital is an academic level 1 trauma center managed by an unchanging dedicated trauma and acute care surgery team. Patients that met criteria for trauma team activation and sustained extensive blast injuries during the Boston Marathon bombing on April 15, 2013, were prospectively enrolled in the study. Bombing patients were enrolled in this study under an existing institutional review board–approved investigation with waiver of informed consent.

After arrival to the

Results

From the large number of patients who presented to our institution immediately after the Boston Marathon bombing, only 10 (n = 10) of the victims met trauma team activation criteria. All trauma team activation patients were admitted due to extensive injuries caused by the explosion. All 10 patients had SDNN and SampEn successfully recorded. Most of the victims were young male individuals (60%) with a mean age of 39.1 years (presenting demographics, Table 1). Despite the relatively stable

Discussion

This report supports the results of previously published studies showing the reproducibility and reliability of heart rate complexity measures in predicting the need of LSIs [1], [4], [6]. Specifically, SampEn predicted LSI and was correlated with ISS in the victims of the Boston Marathon bombing presenting to our institution as trauma team activation patients.

Heart rate variability is generally considered to be a nonspecific indicator of health, mirroring the reaction plasticity of the

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