Elsevier

Resuscitation

Volume 84, Issue 5, May 2013, Pages 626-629
Resuscitation

Clinical paper
The occurrence of shivering in cardiac arrest survivors undergoing therapeutic hypothermia is associated with a good neurologic outcome

https://doi.org/10.1016/j.resuscitation.2012.11.018Get rights and content

Abstract

Background

The incidence of shivering in cardiac arrest survivors who undergo therapeutic hypothermia (TH) is varied. Its occurrence is dependent on the integrity of multiple peripheral and central neurologic pathways. We hypothesized that cardiac arrest survivors who develop shivering while undergoing TH are more likely to have intact central neurologic pathways and thus have better neurologic outcome as compared to those who do not develop shivering during TH.

Methods

Prospectively collected data on consecutive adult patients admitted to a tertiary center from 1/1/2007 to 11/1/2010 that survived a cardiac arrest and underwent TH were retrospectively analyzed. Patients who developed shivering during the cooling phase of TH formed the “shivering” group and those that did not formed the “non-shivering” group. The primary end-point: Pittsburgh Cerebral Performance Category (CPC) scale; good (CPC 1–2) or poor (CPC 3–5) neurological outcome prior to discharge from hospital.

Results

Of the 129 cardiac arrest survivors who underwent TH, 34/94 (36%) patients in the “non-shivering” group as compared to 21/35 (60%) patients in the “shivering” group had good neurologic outcome (P = 0.02). After adjusting for confounders using binary logistic regression, occurrence of shivering (OR: 2.71, 95% CI 1.099–7.41, P = 0.04), time to return of spontaneous circulation (OR: 0.96, 95% CI 0.93–0.98, P = 0.004) and initial presenting rhythm (OR: 4.0, 95% CI 1.63–10.0, P = 0.002) were independent predictors of neurologic outcome.

Conclusion

The occurrence of shivering in cardiac arrest survivors who undergo TH is associated with an increased likelihood of good neurologic outcome as compared to its absence.

Introduction

The use of mild therapeutic hypothermia (TH) has been shown to be associated with improved neurologic outcome when used in patients successfully resuscitated from cardiac arrest.1, 2 However, the beneficial effect of TH in these patients is also dependent on other clinical factors and thus the outcome is varied in this population. For instance the rhythm leading to cardiac arrest, bystander cardiopulmonary resuscitation (CPR) and time to return of spontaneous circulation (ROSC) have been shown to predict outcomes in cardiac arrest survivors undergoing TH.2, 3, 4, 5 Thus, the prognostication of cardiac arrest survivors undergoing TH with regards to neurologic outcome remains challenging.

Shivering is a natural thermoregulatory response of the human body to cooling.6 The occurrence of shivering during TH has been a concern since uncontrolled shivering during this therapy has been associated with longer time to achieve target cooling temperatures and thus may adversely affect outcomes in cardiac arrest survivors.7 However, recent reports suggest that those patients who develop shivering during TH are more likely to have intact neurologic pathways and thus have better neurologic outcomes than those who do not.8, 9 Thus, we hypothesized that those cardiac arrest survivors who underwent TH and developed shivering are more likely to have better neurologic outcome than those who do not develop shivering during TH.

Section snippets

Study population

Consecutive adult patients who were admitted to the Cardiac Intensive Care Unit (CICU) at Hartford Hospital between January 1, 2007 and November 1, 2010 after successful resuscitation from an out-of-hospital or in-hospital cardiac arrest and underwent TH formed the study cohort. The inclusion criteria were: an age of 18–75 years, Glasgow Coma Scale  8 after ROSC, an estimated interval of 5–15 min from the patient's collapse to the first attempt at resuscitation by emergency medical personnel, an

Results

The demographics and clinical characteristics of the study cohort are shown in Table 1. Overall the two groups were relatively similar except for male gender and time to reach target hypothermia. There were significantly more number of males in the “shivering” group as compared to the “non-shivering” group (96% vs. 83% respectively, P = 0.02). The time to reach target hypothermia was significantly more in the “shivering” group as compared to the “non-shivering” group (360 min vs. 273 min

Discussion

Our study shows that in a cohort of cardiac arrest survivors who underwent TH, the occurrence of shivering independently predicts a better neurologic outcome. To our knowledge this is the first published study that shows this association.

Shivering is a natural thermoregulatory response of the body to lowering of core temperature and has been shown to require multiple peripheral and central neurologic pathways for its manifestation (Fig. 2).13, 14, 15 The primary center of shivering in the brain

Limitations

This is a retrospective study conducted on prospective data collected at a single large tertiary center and limits the extent to which the results can be generalized. Our study findings may not be applicable to those hypothermia protocols which administer paralytic agents to all cardiac arrest patients undergoing TH as a prophylactic measure to prevent shivering. Retrospective studies are limited by the inability to adjust for confounding factors and referral bias. Although adjustment for

Conclusions

In cardiac arrest survivors undergoing therapeutic hypothermia, the occurrence of shivering is independently associated with a good neurologic outcome as compared to its absence. Shivering can be used as an additional clinical predictor of good neurologic outcome during prognostic evaluation in patients undergoing TH.

Disclosures

Financial disclosure: Justin Lundbye, speaker for ZOLL Temperature Management.

Unlabeled/unapproved use disclosure: ICY Catheter© for induction of therapeutic hypothermia.

References (15)

There are more references available in the full text version of this article.

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    Physiologic response to targeted temperature management provides another avenue for insight into the potential for neurologic recovery. The presence of shivering, the amount of patient heat generation (derived from the inverse average water temperature of cooling devices), and the presence of bradycardia (<60 beats/min) during the induction and maintenance of temperature management are each associated with a favorable neurologic outcome.110–112 Preliminary imaging of the brain, usually a noncontrast computed tomography scan, is important to exclude intracranial causes of collapse and injury incurred at the time of collapse.

  • Neuromuscular blockade requirement is associated with good neurologic outcome in cardiac arrest survivors treated with targeted temperature management

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    It is well established that these variables are associated with good outcomes in cardiac arrest survivors. Nair et al. demonstrated the association between shivering during therapeutic hypothermia and increased chances of good neurologic outcome in cardiac arrest survivors undergoing therapeutic hypothermia [25]. The occurrence of shivering implies an intact thermoregulatory response of the brain against cooling.

  • Canadian Cardiovascular Society/Canadian Cardiovascular Critical Care Society/Canadian Association of Interventional Cardiology Position Statement on the Optimal Care of the Postarrest Patient

    2017, Canadian Journal of Cardiology
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    However, use of these agents might be associated with intensive care unit-acquired weakness, altered neurologic examinations, and masking of seizures or myoclonus. Furthermore, it has been postulated that shivering patients might have less anoxic brain injury and more intact central neurologic pathways and that shivering might be an independent predictor of favourable neurological outcomes.112 There are no randomized data available regarding the use of neuromuscular blocking agents in OHCA patients and observational studies have shown conflicting results regarding the safety and efficacy of these agents in this population.113,114

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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.2012.11.018.

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