Elsevier

Resuscitation

Volume 81, Issue 9, September 2010, Pages 1117-1122
Resuscitation

Clinical paper
Therapeutic hypothermia after cardiac arrest: A retrospective comparison of surface and endovascular cooling techniques

https://doi.org/10.1016/j.resuscitation.2010.05.001Get rights and content

Abstract

Objectives

Therapeutic hypothermia (32–34 °C) is recommended for comatose survivors of cardiac arrest; however, the optimal technique for cooling is unknown. We aimed to compare therapeutic hypothermia using either surface or endovascular techniques in terms of efficacy, complications and outcome.

Setting

Thirty-bed teaching hospital intensive care unit (ICU).

Patients

All patients (n = 83) undergoing therapeutic hypothermia following cardiac arrest over a 2.5-year period. The mean age was 61 ± 16 years; 88% of arrests occurred out of hospital, and 64% were ventricular fibrillation/tachycardia.

Interventions

Therapeutic hypothermia was initiated in the ICU using iced Hartmann's solution, followed by either surface (n = 41) or endovascular (n = 42) cooling; choice of technique was based upon endovascular device availability. The target temperature was 32–34 °C for 12–24 h, followed by rewarming at a rate of 0.25 °C h−1.

Measurements and main results

Endovascular cooling provided a longer time within the target temperature range (p = 0.02), less temperature fluctuation (p = 0.003), better control during rewarming (0.04), and a lower 48-h temperature load (p = 0.008). Endovascular cooling also produced less cooling-associated complications in terms of both overcooling (p = 0.05) and failure to reach the target temperature (p = 0.04). After adjustment for known confounders, there were no differences in outcome between the groups in terms of ICU or hospital mortality, ventilator free days and neurological outcome.

Conclusion

Endovascular cooling provides better temperature management than surface cooling, as well as a more favorable complication profile. The equivalence in outcome suggested by this small study requires confirmation in a randomized trial.

Introduction

Cardiovascular disease remains a leading cause of death in the developed world and survival from cardiac arrest with good neurological outcome is uncommon. In the United Kingdom less than 30% of patients admitted to the intensive care unit (ICU) following cardiac arrest survive to hospital discharge1 and the majority of those who die do so as a result of neurological injury.2

Two prospective randomized controlled studies3, 4 and a meta-analysis5 have shown benefit in survival and neurological outcome associated with a 12–24 h period of mild hypothermia (32–34 °C). Current guidance from the International Liaison Committee on Resuscitation is that therapeutic hypothermia (TH) should be instituted where possible for comatose survivors of cardiac arrest.6 Several controversies exist concerning TH, especially with regard to the most efficient cooling technique, duration of hypothermia, and patient selection.6

Therapeutic hypothermia can be induced rapidly by infusion of cold (4 °C) crystalloid solution7 following which hypothermia is maintained using either surface or endovascular techniques. Surface cooling methods are effective but can be labor intensive for the nursing staff and may prevent access to the patient. Endovascular cooling is also effective and permits precise control of body temperature, but involves insertion of a large (8.5 Fr) gauge catheter into the femoral vein, which is invasive.

We have been using TH in our 30-bedded ICU (located within a university affiliated, teaching hospital) since July 2005, employing both surface and endovascular cooling techniques. Our local policy is that all cardiac arrests receive TH, irrespective of primary rhythm or arrest location unless the patient has a contraindication. We carried out a retrospective study on all patients undergoing TH following cardiac arrest over a 30-month period, to address two questions:

  • (1)

    Do endovascular or surface cooling techniques differ in effectiveness, in terms of time spent at target temperature, induction of cooling, re-warming and prevention of rebound hyperthermia?

  • (2)

    Does choice of cooling technique affect incidence of complications or outcome?

Section snippets

Materials and methods

A local research ethics committee reviewed the proposed study and waived the need for a full ethics submission, as the study met the national criteria for service evaluation.

Statistical analysis

Between-group comparisons were made using Student's t-test, Fischer's Exact Test and analysis of covariance where appropriate. Comparison of binary outcomes (mortality, neurological outcome) was via logistic regression. The variable selection process was made a priori, based upon important variables identified in the literature.6 These included: cooling technique, APACHE II score, time to ROSC, and primary arrest rhythm (ventricular fibrillation/pulseless ventricular tachycardia versus

Demographics and cardiac arrest details

A total of 83 patients receiving TH were identified, of which 42 underwent endovascular cooling and the remaining 41 underwent surface cooling. Between-group comparisons for demographics, cardiac arrest details, primary outcomes and complications are summarized in Table 1, Table 2. The two groups were comparable in terms of age, sex, weight and APACHE II scores. The majority (87.5%) of cardiac arrests was “out of hospital” and in 63.9% the primary rhythm was ventricular fibrillation or

Discussion

The role of TH in comatose survivors of cardiac arrest is increasingly recognized,3, 4, 5 and there is increasing evidence that a standardised approach including coronary revascularization and therapeutic hypothermia may enhance survival.9 The optimal technique for delivering TH is debatable; the International Liaison Committee on Resuscitation identifies “optimal cooling technique – internal versus external” as a critical knowledge gap.6 In their 2008 consensus statement, the Committee

Conclusion

Endovascular cooling appears more efficacious than surface cooling in terms of temperature control for TH following cardiac arrest; this is also associated with a better temperature-associated complication profile. After adjustment for known confounders, we were unable to show a difference in outcome with either technique. This requires confirmation in a randomized control trial.

Conflict of interest statement

None to declare.

References (21)

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    The characteristics of included studies and their enrolled patients and outcomes are summarized in Table 1. Three studies were randomized trials 23–25; four were prospective cohort studies 22,28,32,33; and three were retrospective case-control studies.37–39 Two were secondary analyses of randomized trials: one compared two target temperature ranges and another compared two protocols for duration of IH in patients resuscitated from CA.40,41

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    Hypothermia was also credited with activating the production of cyclic guanosine monophosphate (cGMP), which is associated with the expressions of the PGC-1α and NRF-1 [9,24]. Kinase Akt has been observed to be activated by hypothermia in some studies [10,11], while Akt phosphorylated NRF-1 and improved the nuclear translocation of NRF-2. The accumulation of NRF-1 and NRF-2 was also shown to lead to gene activation for mitochondrial biogenesis [28].

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A Spanish translated version of the summary of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2010.05.001.

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