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Original Investigation |

Effect of Prehospital Induction of Mild Hypothermia on Survival and Neurological Status Among Adults With Cardiac Arrest:  A Randomized Clinical Trial

Francis Kim , MD1; Graham Nichol, MD, MPH1; Charles Maynard, PhD2; Al Hallstrom, PhD3; Peter J. Kudenchuk, MD1; Thomas Rea, MD, MPH1; Michael K. Copass, MD4; David Carlbom, MD1; Steven Deem, MD5; W. T. Longstreth Jr, MD4,6; Michele Olsufka, RN1; Leonard A. Cobb, MD1
[+] Author Affiliations
1Department of Medicine, School of Medicine, University of Washington, Seattle
2Department of Health Services, School of Public Health, University of Washington, Seattle
3Department of Biostatistics, School of Public Health, University of Washington, Seattle
4Department of Neurology, School of Medicine, University of Washington, Seattle
5Department of Anesthesiology, School of Medicine, University of Washington, Seattle
6Department of Epidemiology, School of Public Health, University of Washington, Seattle
JAMA. 2014;311(1):45-52. doi:10.1001/jama.2013.282173.
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Importance  Hospital cooling improves outcome after cardiac arrest, but prehospital cooling immediately after return of spontaneous circulation may result in better outcomes.

Objective  To determine whether prehospital cooling improves outcomes after resuscitation from cardiac arrest in patients with ventricular fibrillation (VF) and without VF.

Design, Setting, and Participants  A randomized clinical trial that assigned adults with prehospital cardiac arrest to standard care with or without prehospital cooling, accomplished by infusing up to 2 L of 4°C normal saline as soon as possible following return of spontaneous circulation. Adults in King County, Washington, with prehospital cardiac arrest and resuscitated by paramedics were eligible and 1359 patients (583 with VF and 776 without VF) were randomized between December 15, 2007, and December 7, 2012. Patient follow-up was completed by May 1, 2013. Nearly all of the patients resuscitated from VF and admitted to the hospital received hospital cooling regardless of their randomization.

Main Outcomes and Measures  The primary outcomes were survival to hospital discharge and neurological status at discharge.

Results  The intervention decreased mean core temperature by 1.20°C (95% CI, −1.33°C to −1.07°C) in patients with VF and by 1.30°C (95% CI, −1.40°C to −1.20°C) in patients without VF by hospital arrival and reduced the time to achieve a temperature of less than 34°C by about 1 hour compared with the control group. However, survival to hospital discharge was similar among the intervention and control groups among patients with VF (62.7% [95% CI, 57.0%-68.0%] vs 64.3% [95% CI, 58.6%-69.5%], respectively; P = .69) and among patients without VF (19.2% [95% CI, 15.6%-23.4%] vs 16.3% [95% CI, 12.9%-20.4%], respectively; P = .30). The intervention was also not associated with improved neurological status of full recovery or mild impairment at discharge for either patients with VF (57.5% [95% CI, 51.8%-63.1%] of cases had full recovery or mild impairment vs 61.9% [95% CI, 56.2%-67.2%] of controls; P = .69) or those without VF (14.4% [95% CI, 11.3%-18.2%] of cases vs 13.4% [95% CI,10.4%-17.2%] of controls; P = .30). Overall, the intervention group experienced rearrest in the field more than the control group (26% [95% CI, 22%-29%] vs 21% [95% CI, 18%-24%], respectively; P = .008), as well as increased diuretic use and pulmonary edema on first chest x-ray, which resolved within 24 hours after admission.

Conclusion and Relevance  Although use of prehospital cooling reduced core temperature by hospital arrival and reduced the time to reach a temperature of 34°C, it did not improve survival or neurological status among patients resuscitated from prehospital VF or those without VF.

Trial Registration  clinicaltrials.gov Identifier: NCT00391469

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Figure 1.
Study Flow Diagram

No patients were lost to follow-up. aSome patients were excluded for more than 1 reason. bIncluded traumatic cardiac arrest, age younger than 18 years, no esophageal temperature, or no intravenous catheter. cOf the 1364 patients enrolled, prehospital emergency medical services records and discharge data from only 1359 patients were used for the analyses of primary outcomes because 5 patients were later found to be incarcerated at the time of enrollment, thus data from these patients were not included in any of the analyses.

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Figure 2.
The Proportion of Comatose Patients Achieving Either Death Without Awakening or Awakening as a Function of Days After Cardiac Arrest for Enrolled Patients

The area between the 2 curves represents the proportion of patients who remain comatose. All patients at time = 0 are comatose and over time either awaken or die without awakening. A, There were 568 patients with ventricular fibrillation (VF) and known event times (284 in intervention group and 284 in control group). For patients with initial rhythm of VF at 7 days, 157 patients died without awakening (28%), 355 had awakened (62%), and 56 were still comatose (10%). At 30 days, 34 more patients died without awakening, 14 more had awakened, and 8 patients remained comatose. B, There were 771 patients without VF but with known event times (395 in the intervention group and 376 in the control group). At 7 days, 566 patients died without awakening (73%), 138 had awakened (18%), and 67 were still comatose (9%). At 30 days, 46 more patients died without awakening, 8 more had awakened, and 13 patients remained comatose.

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