Elsevier

Heart, Lung and Circulation

Volume 23, Issue 11, November 2014, Pages 1029-1035
Heart, Lung and Circulation

Review
Extracorporeal-Assisted Rewarming in the Management of Accidental Deep Hypothermic Cardiac Arrest: A Systematic Review of the Literature

https://doi.org/10.1016/j.hlc.2014.06.011Get rights and content

A systematic review of the literature surrounding the use of Extra-Corporeal Assisted Rewarming (ECAR) in patients presenting with deep hypothermia or hypothermic cardiac arrest was undertaken using a structured protocol.

Thirty-one papers were deemed suitable for review, 13 of these were of sufficient quality to permit systematic data analysis. The primary outcome measure was survival to hospital discharge. The secondary outcome measure was functional neurological status at last follow-up.

Analysis revealed a 67.7% survival to discharge and a 61.5% rate of good neurological recovery for patients presenting with pure hypothermic cardiac arrest. This was in marked contrast to a 23.4% survival and a 9.4% rate of good neurological outcome in those presenting with a mixed hypoxic/hypothermic arrest.

Other data revealed a survival benefit for patients presenting with deep hypothermia without cardiac arrest treated with ECAR compared to those treated with conventional rewarming techniques.

Hypoxic arrest, serum potassium >10mmol/L and presenting rhythm of asystole were found likely be significant predictors of poor outcome. Innovative reperfusion and rewarming strategies are also reviewed.

Introduction

Accidental hypothermia is defined as a core temperature of <350 C. Deep hypothermia is defined as a core temperature of <280 C. At this temperature, cardiac instability, ventricular arrhythmias and cardiac arrest are common.

Traditional teaching surrounding the management of the hypothermic patient in cardiac arrest states that the patient is ‘not dead until they are warm and dead’. This was based predominantly on isolated case reports of successful prolonged resuscitation in hypothermic patients.

The traditional methods of rewarming included warm air, warm blankets, warm intravenous fluids and warm internal lavage of body cavities including the stomach, bladder, peritoneum and thorax. As deep hypothermic circulatory arrest became commonly employed in cardiac surgery for complex reconstructive surgery the concept of extracorporeal rewarming for hypothermic arrest was born. The first successful cases were reported in 1967 [1], [2].

However, despite 45 years passing since the first reported successes, we still have only a limited understanding of which patients will do well with extracorporeal resuscitation. The goals of therapy have, rightfully, shifted away from mere survival to high-functioning survival.

We have recently and successfully managed two cases of deep hypothermic cardiac arrest with extracorporeal rewarming. This experience is extremely unusual in Australia, only three cases having been reported previously, and only two of these being managed with extracorporeal rewarming. As such, it has encouraged us to review the existing literature to help establish recommendations for the management of this patient population.

Section snippets

Participants

All patients undergoing extracorporeal rewarming for accidental deep hypothermia.

Outcome Measures

The primary outcome measure is survival to hospital discharge.

The secondary outcome measure is functional neurological status at last follow-up.

Search Strategy

A systematic review of the published English-language literature was undertaken. Electronic searches of Medline, PubMed, EMBASE, Cochrane Database of Systematic Reviews and Google Scholar were undertaken using the search terms “Extracorporeal Membrane Oxygenation” “ECMO”

Comparative Series

A single comparative study by Morita et al. [3] between hypothermic patients treated with conventional rewarming techniques (between 1992 and 2001) and patients treated with extracorporeal rewarming (between 2001 and 2009) at a single centre was analysed. Not all patients in this series had suffered cardiac arrest. The results are presented in Table 1.

Subgroup analysis of the small number (n = 13) of patients that suffered cardiac arrest was also performed. Survival was 14.3% (1/7) in the

Discussion

The results of this review clearly demonstrate the value of ECAR in the management of hypothermic cardiac arrest. The comparative data from Morita et al. [3], although open to confounding, is compelling evidence for the use of ECAR in both cardiac arrest and also those without cardiac arrest. Reassuringly, the study also demonstrated (with no ECAR-related complications) that ECAR is a safe treatment modality in this situation.

Analysis of the 12 case series, with 247 patients, demonstrated three

Hypoxic Arrest

The dismal prognosis surrounding cardiac arrest secondary to hypoxia in hypothermic conditions is obvious from the above data. It is now clear that the protective effects of hypothermia are limited in this setting. Despite the occasional promising case report [23], [27] the question of whether it is justifiable to embark on a highly invasive and costly resuscitation effort in such a futile setting must be asked.

The reality of clinical medicine however, does not always present us with clear-cut

Initial Cold Reperfusion

No papers reviewed reported the use of an initial period of cold reperfusion prior to rewarming.

A recent study from di Mauro et al. [33] demonstrated an impressive reduction in adverse neurological events with an initial period of cold reperfusion at 20 degrees for 10 minutes following aortic arch surgery using Deep Hypothermic Circulatory Arrest (DHCA). The control group had a neurological event rate of 18.7% compared to 7.7% in the cold reperfusion group. Although these results may be

Acknowledgements, Disclosures and Conflicts of Interest

We have no disclosures or conflicts of interest to declare.

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