Elsevier

Resuscitation

Volume 84, Issue 5, May 2013, Pages 620-625
Resuscitation

Clinical paper
Does induction of hypothermia improve outcomes after in-hospital cardiac arrest?

https://doi.org/10.1016/j.resuscitation.2012.12.009Get rights and content

Abstract

Introduction

Hypothermia improves neurologic recovery compared to normothermia after resuscitation from out-of-hospital ventricular fibrillation, but may or may not be beneficial for patients resuscitated from in-hospital cardiac arrest. Therefore, we evaluated the effect of induced hypothermia in a large cohort of patients with in-hospital cardiac arrest.

Methods

Retrospective analysis of multi-center prospective cohort of patients with in-hospital cardiac arrest enrolled in an ongoing quality improvement project. Included were adults with a pulseless event in an in-patient hospital ward of a participating institution who achieved restoration of spontaneous circulation between 2000 and 2009. The exposure of interest was induced hypothermia. The primary outcome was survival to discharge. The secondary outcome was neurological status at discharge. Analyses evaluated all eligible patients; those with a shockable rhythm; or those with endotracheal tube inserted after resuscitation; and the effect of no hypothermia versus hypothermia (lowest temperature > 32 °C but  34 °C) versus overcooled (≤32 °C). Associations were assessed using propensity score methods.

Results

Included were 8316 patients with complete data, of whom 214 (2.6%) had hypothermia induced and 2521 (30%) survived to discharge. Of patients reported to receive hypothermia, only 40% were documented as achieving a temperature between 32 °C and 34 °C. Adjusted for known potential confounders using propensity score methods, induced hypothermia was associated with an odds ratio of survival of 0.90 (95% confidence interval: 0.65, 1.23; p-value = 0.49) compared to no hypothermia. Induced hypothermia was associated with an odds ratio of neurologically-favorable survival of 0.93 (95% confidence interval: 0.65, 1.32; p-value = 0.68) compared to no hypothermia. For patients with shockable first-recorded rhythm, induced hypothermia was associated with an odds ratio of survival of 1.43 (95% confidence interval: 0.68, 3.01; p-value = 0.35) compared to no hypothermia.

Conclusion

Hypothermia is induced infrequently in patients resuscitated from in-hospital cardiac arrest with only 40% achieving target temperatures. Induced hypothermia was not associated with improved or worsened survival or neurologically-favorable survival. The lack of benefit in this population may reflect lack of effect, inefficient application of the intervention, or residual confounding. High-quality controlled studies are required to better characterize the effect of induced hypothermia in this population.

Introduction

Hypothermia may reduce production of deleterious molecules, cerebral oxygen demand, and intracranial pressure in patients resuscitated from cardiac arrest, and thereby the final extent of their neurologic injury.1 Two trials showed hypothermia improved neurologic function versus normothermia in patients resuscitated from out-of-hospital ventricular fibrillation.2, 3

The burden of in-hospital4, 5 and out-of-hospital6 cardiac arrest are similar. While the physiology of brain injury is similar regardless of the location of arrest,7 patients resuscitated from in-hospital cardiac arrest (IHCA) are more likely than those resuscitated from out-of-hospital arrest to die with multiple organ failure.8 Thus, current care guidelines recommend induction of hypothermia after resuscitation regardless of the location of arrest.9 But no large observational study or trial has evaluated induced hypothermia in patients resuscitated from IHCA. We evaluated the effect of hypothermia in this population.

Section snippets

Methods

This study was approved by the Get With the Guidelines-Resuscitation (GWTG-R) scientific advisory board. The University of Washington Institutional Review Board (IRB) determined that this retrospective analysis of deidentified data was exempt from IRB review.

Study design

We used data from GWTG-R, an ongoing quality improvement project for IHCA. Participating hospitals voluntarily report data regarding in-hospital resuscitations as identified by an emergency resuscitation response by medical personnel and a resuscitation record. In GWTG-R, cardiac arrest is defined as patient unresponsiveness, apnea, and absence of a central pulse. The AHA provides quality control and oversight for all GWTG-R data collection, analysis, and reporting. Additional details regarding

Patient population

Included were adults who had IHCA between 2000 and 2009 in the general in-patient hospital ward and achieved restoration of spontaneous circulation. For an admission containing multiple cardiac arrest events, only the first arrest was included. Both primary and secondary analyses excluded patients who arrested in emergency departments, intensive care units, operating rooms, procedure areas, or post-procedural areas at the time of their arrest due to clinical circumstances associated with these

Exposure and outcomes

The primary exposure of interest was induced hypothermia after resuscitation. In GWTG-R, this was elicited as “Was induced hypothermia initiated after return of circulation … achieved?” without any specific definition of hypothermia. Sensitivity analyses cross-validated “induced hypothermia” by confirming that the lowest temperature in the first 24 h post event was  34 °C among patients treated between 2004 and 2009, when temperature data were included in GWTG-R.

The primary outcome was survival to

Data analysis

Baseline patient characteristics were summarized descriptively. The association between exposure and outcome was determined by covariate adjustment using propensity scores (PS).14, 15 This method uses logistic regression to predict the probability that an individual patient was exposed to the intervention of interest (e.g., hypothermia), with adjustment for factors recognized as potential confounders based on prior studies. The latter included: age, gender, race (white, black, other), prior

Results

10,860 patients were eligible for inclusion in the study (Fig. 1). 8316 (76.6%) patients from 454 hospitals had complete data and were used in the analysis. Patient demographics and clinical characteristics were summarized in Table 1. Patients had mean age of 67 years, and 52% had male gender. 73% were white, and less than 6% were Hispanic. The majority lived at home prior to the event, while only 8% resided in an acute care facility. 27% were monitored before the event, and 59% of events were

Discussion

In this retrospective analysis of patients with ICHA, only 2.6% of patients had hypothermia induced after resuscitation. A majority of treated patients were not documented as achieving the intended range of hypothermia or were overcooled. Induced hypothermia was not associated with survival or neurologic outcome.

Prior trials that reported benefit with induced hypothermia in patients resuscitated from cardiac arrest were conducted in different populations. The HACA trial included 275 comatose

Conclusion

Hypothermia is induced infrequently in patients resuscitated from IHCA. A minority of treated patients were reported as receiving hypothermia or achieving target temperatures. The observed absence of evidence of survival or neurological benefit in treated patients may be evidence of the absence of effect, or inefficient application of the intervention or residual confounding. Application of hypothermia should include monitoring of adherence to treatment targets. High-quality controlled studies

Conflict of interest statement

We wish to confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome beyond those stated below.

Nichol has applied for a grant from the National Heart Lung Blood Institute to conduct a randomized trial of different durations of induced hypothermia in patients resuscitated from out-of-hospital cardiac arrest, with third-party cost sharing to be provided by C.R.

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    A Spanish translated version of the abstract of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2012.12.009.

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