• Effect of prehospital induction of mild hypothermia on survival and neurological status among adults with cardiac arrest: a randomized clinical trial

    by Alan Batt. Last modified: 24/02/14

    thypotherm

    As experts in resuscitation techniques, paramedics need to understand the science and the data behind the interventions they perform – it’s looking like the writing is on the wall for prehospital induction of hypothermia in ROSC!

    Summary

    • Randomized control trial
    • 1359 patients enrolled with ROSC
      • 583 with Ventricular Fibrillation (VF); 776 without Ventricular Fibrillation
    • Intervention group (n=688) – rapid infusion of 2L of 4C normal saline, 7-10mg of pancuronium and 1-2mg of diazepam
    • Control group (n=671) – standard prehospital care (no cooling)
    • Intervention group had more re-arrests prehospital than the control group.
    • Increased diuretic use and pulmonary edema on first chest x-ray in intervention group.
    • No evidence that prehospital initiation of therapeutic hypothermia improves survival or neurological status among patients.

    A robustly designed and executed study, results from this can be taken to be accurate for the patient population studied. Some limitations include:

    • Intervention group were more likely to re-arrest which may have lead to increased deaths in long-term.
    • The study was conducted in an EMS system world-renowned for excellent results from prehospital resuscitation (including high rates of bystander CPR and AED use – King County EMS, WA – averaging a 57% survival rate from OHCA – http://www.kingcounty.gov/healthservices/health/news/2013/13090401.aspx).
    • Results on the quality of prehospital CPR and the variation in temperature are unknown.
    • Factors that influence survival that were not included such as post-resuscitation care (ventilation, medications etc.)

     
    Kim F1, Nichol G1, Maynard C2, Hallstrom A3, Kudenchuk PJ1, Rea T1, Copass MK4, Carlbom D1, Deem S5, Longstreth WT Jr6, Olsufka M1, Cobb LA1. Effect of prehospital induction of mild hypothermia on survival and neurological status among adults with cardiac arrest: a randomized clinical trial. JAMA. 2014 Jan 1;311(1):45-52. PMID: 24240712.

    Abstract

    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 & 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 & measurements

    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.

    References

     
    1.

    Kim F1, Nichol G1, Maynard C2, Hallstrom A3, Kudenchuk PJ1, Rea T1, Copass MK4, Carlbom D1, Deem S5, Longstreth WT Jr6, Olsufka M1, Cobb LA1. Effect of prehospital induction of mild hypothermia on survival and neurological status among adults with cardiac arrest: a randomized clinical trial. JAMA. 2014 Jan 1;311(1):45-52. PMID: 24240712.

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    Alan Batt

    Alan Batt

    Paramedic, educator, researcher
    Alan is a critical care paramedic, paramedic educator and prehospital researcher, currently working around the world as an educator and researcher. He has previously worked and studied across Europe, North America and the Middle East. He holds a Graduate Certificate in Intensive Care Paramedic Studies, and an MSc in Critical Care. His main interests are in care of the elderly, end-of-life care, patient safety, professionalism (including role and identity), and paramedic education.

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