Intervention Review

Hypothermia to reduce neurological damage following coronary artery bypass surgery

  1. Karen Rees1,*,
  2. Morven Beranek-Stanley2,
  3. Margaret Burke3,
  4. Shah Ebrahim4

Editorial Group: Cochrane Heart Group

Published Online: 22 JAN 2001

Assessed as up-to-date: 23 OCT 2000

DOI: 10.1002/14651858.CD002138

How to Cite

Rees K, Beranek-Stanley M, Burke M, Ebrahim S. Hypothermia to reduce neurological damage following coronary artery bypass surgery. Cochrane Database of Systematic Reviews 2001, Issue 1. Art. No.: CD002138. DOI: 10.1002/14651858.CD002138.

Author Information

  1. 1

    Warwick Medical School, University of Warwick, Division of Health Sciences, Coventry, UK

  2. 2

    University of Bristol, c/o Department of Social Medicine, Bristol, UK

  3. 3

    University of Bristol, Department of Social Medicine, Bristol, UK

  4. 4

    London School of Hygiene and Tropical Medicine, Department of Non-communicable Disease Epidemiology, London, UK

*Karen Rees, Division of Health Sciences, Warwick Medical School, University of Warwick, Coventry, CV4 7AL, UK. Karen.Rees@warwick.ac.uk. rees_karen@yahoo.co.uk.

Publication History

  1. Publication Status: Stable (no update expected for reasons given in 'What's new')
  2. Published Online: 22 JAN 2001

SEARCH

 

Abstract

  1. Top of page
  2. Abstract
  3. Plain language summary

Background

Coronary artery bypass surgery (CABG) may be life saving, but known side effects include neurological damage and cognitive impairment. The temperature used during cardiopulmonary bypass (CPB) may be important with regard to these adverse outcomes, where hypothermia is used as a means of neuroprotection.

Objectives

To assess the effectiveness of hypothermia during CABG in reducing neurological damage and subsequent cognitive deficits.

Search methods

The Cochrane Controlled Trials Register was searched for randomised controlled trials (RCT) and this was updated by searching MEDLINE and EMBASE to December 1999 using database specific RCT filters. Reference lists of retrieved articles were searched and experts in the field were contacted.

Selection criteria

Only RCTs were considered. All patients undergoing CABG, either first time or revisions, elective or emergency procedures, were included. Any hypothermia protocol was considered. Only trials reporting neurological outcomes were included.

Data collection and analysis

Studies were selected independently and data were extracted from the source papers independently by two reviewers. Authors were contacted for further information. Studies were combined with meta-analysis where appropriate, and meta-regression was used to explore heterogeneity.

Main results

There was a trend towards a reduction in the incidence of non fatal strokes in the hypothermic group (OR 0.68 (0.43, 1.05)). Conversely, there was a trend for the number of non stroke related perioperative deaths to be higher in the hypothermic group (OR 1.46 (0.9, 2.37)). There was no evidence to suggest that hypothermia had an effect on the incidence of non fatal myocardial infarction (OR 1.05 (0.81, 1.37)), but the incidence of another marker of myocardial damage, low output syndrome, was higher in the hypothermic group (OR 1.21 (0.99, 1.48). When pooling all "bad" outcomes (stroke, perioperative death, myocardial infarction, low output syndrome, intra aortic balloon pump use) there was no significant advantage of either hypothermia or normothermia (OR 1.07 (0.92, 1.24)). Only 4 of 17 trials reported neuropsychological function as an outcome.

Authors' conclusions

This review could find no definite advantage of hypothermia over normothermia in the incidence of clinical events. Hypothermia was associated with a reduced stroke rate, but this is off set by a trend towards an increase in non stroke related perioperative mortality and myocardial damage. There is insufficient data to date to draw any conclusions about the use of mild hypothermia. Similarly, there is insufficient data to date to comment on the effect of temperature during CPB on subtle neurological deficits, and further trials are needed in these areas.

 

Plain language summary

  1. Top of page
  2. Abstract
  3. Plain language summary

There is not enough evidence to show that lowering body temperature can reduce nerve damage during coronary artery bypass surgery.

For people with severe coronary artery (heart) disease, bypass surgery can be life saving. However, bypass surgery is sometimes associated with neurological complications, where very occasionally patients may suffer a stroke, or more commonly memory or personality may be affected. The temperature used during bypass surgery may influence these adverse effects. Reducing the temperature during surgery (hypothermia) may protect the brain and reduce the risk of complications. The review of trials found that there was not enough evidence to show the protective effects of hypothermia. More research is needed.