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J Thorac Cardiovasc Surg 1999;118:420-421
© 1999 Mosby, Inc.

CARDIOPULMONARY SUPPORT AND PHYSIOLOGY

Commentary

	Introduction

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In this provocative study, Taggart and colleagues have apparently been unable to demonstrate any meaningful differences in postoperative cognitive outcomes in patients undergoing coronary revascularization with or without the use of cardiopulmonary bypass (CPB). Although there may be some significant methodologic points at issue relating to the detection of cognitive dysfunction and revolving around the use of group mean analysis, as used here, versus incidence analysis, as has been recommended elsewhere, ¹ the clinical message appears to be that there are no meaningful differences in cognitive outcomes irrespective of whether or not CPB is used. Before this result is uncritically accepted and generalized, however, careful consideration must be given to the specific conditions of this study.

In the first instance, this study was not randomized. The 50 patients comprising the CPB group were in fact drawn as a subset from 150 patients undergoing a separate, randomized controlled trial of an anti-inflammatory agent. Since this group was matched post hoc for age and sex with the 25 patients in whom CPB was not used (no CPB), and necessarily included only those patients with complete data sets, CPB patients with significant complications (eg, mortality, stroke, important hemodynamic complications) or those lost to follow-up would not have been represented in the CPB comparison group. This fact alone raises the possibility of significant inadvertent bias in favor of the CPB group.

Irrespective of this confound, however, the fact remains that for these selected groups these data, as analyzed, do not appear to show any meaningful differences in outcome ascribable to use of CPB. What else is different about these groups? Certainly the average age of the 2 study groups is considerably younger than that for those undergoing surgical coronary revascularization in North America. On the basis of the latest figures available from The Society of Thoracic Surgeons Adult Cardiac National Database, the average age of patients undergoing coronary artery bypass grafting (CABG) in North America in 1996 was 64.7 ± 10.6 years. ² This is in contrast to the mean age of 58.9 ± 10 years in the current study. Is this germane? The risks of neurologic and cognitive injury after CPB are largely determined by age. In a prospective study of 2108 patients undergoing CABG, 32% of patients were aged 70 years or older, and older age was shown to be a significant independent risk factor for both stroke (type I) and deterioration of intellectual function (type II) outcomes. ³ Others have also shown a specific association between age and postoperative cognitive dysfunction in patients undergoing conventional CABG. ⁴ Given that the proportion of CABG patients older than 70 years exceeds 30% in most clinical practices in North America, before determining operative strategy on the basis of the results of the current study, we must be fully aware that although these results may apply, they may well apply only to those patients younger than 60 years.

	References

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1. Murkin JM, Stump DA, Blumenthal JA, McKhann G. Defining dysfunction: group means versus incidental analysis—a statement of consensus. Ann Thorac Surg 1997;64:904-5.
   
2. Shroyer ALW, Plomondon ME, Grover FL, Edwards FH. The 1996 coronary artery bypass risk model: The Society of Thoracic Surgeons Adult Cardiac National Database. Ann Thorac Surg 1999;67:1205-8.[Abstract/Free Full Text]
   
3. Roach GW, Kanchuger M, Mora Mangano CM, et al. Adverse cerebral outcomes after coronary artery bypass surgery. N Engl J Med 1996;335:1857-63.[Abstract/Free Full Text]
   
4. Newman MF, Croughwell ND, Blumenthal JA, et al. Effect of aging on cerebral autoregulation during cardiopulmonary bypass: association with postoperative cognitive dysfunction. Circulation 1994:90(5 Pt 2):II243-9.
   

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This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): John M. Murkin Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Murkin, J. M. Search for Related Content PubMed PubMed Citation Articles by Murkin, J. M.