J Thorac Cardiovasc Surg 2000;120:1014
© 2000 The American Association for Thoracic Surgery
Reply
Richard Engelman, MD,
A. Bernard Pleet, MD
Division of Cardiac Surgery
Department of Surgery
Division of Neurology
Department of Medicine
Baystate Medical Center
759 Chestnut St Springfield, MA 01107
Reply to the Editor:
We thank Gaudino and Possati for their comments on our recent article,
1 which was, in turn, prompted by their publication. 2 They have made 5 specific points, and we will comment on them in turn.
- They indicate that including patients as "warm" who have had perfusion at 32°C is methodologically incorrect. They state that this is "putting together patients with different degrees of neurologic risk." Inherently this may be true, but in their report 2 normothermic perfusion is considered to include patients who have been perfused at 34°C or more. This is not clearly different from patients perfused at 32°C. Patients who are protected at 34°C would be equally well protected at 32oC. Since they chose to combine tepid (34°C) with normothermic perfusion, we chose to group the patients similarly, and our results reflect this comparison of tepid-normothermic versus cold.
- The second point concerns the definition of intraoperative stroke. As noted in the published article, in each case stroke was diagnosed on the basis of computed tomographic (CT) scan evidence. Twelve patients had an intraoperative event and 1 patient had a postoperative cerebral vascular accident (CVA). Only the 12 intraoperative CVAs were discussed in the article, and they prompted our conclusion that there was no difference in degree of intraoperative injury on the basis of perfusion temperature.
- The CT analysis for diagnosis of CVA was prospective in our initial study, 3 as described in the published article. The subsequent analysis of cerebral infarct volume was indeed retrospective. However, whether the volume analysis is prospective or retrospective should not affect the conclusion of the article. In either case, there was no demonstrable difference between warm and cold perfusion.
- It is true that the number of strokes in our series, 12, is smaller than the 25 intraoperative CVAs in their report. However, there is a clear distinction between the small and large strokes in our series. As noted by Gaudino and Possati, it is likely that only the large strokes were appreciated in their series. If one were to consider only the large infarcts, there would be only 6 strokes, 3 in each group, severely limiting the statistical power of our analysis. The absence of statistical power is clearly true, and we agree that the only way to resolve this issue is to conduct a new randomized trial with very large numbers of patients, which is unlikely to be achievable. However, our findings of no difference in small or large infarcts on the basis of temperature means that a huge patient base would be necessary to achieve statistical validity. We do not believe such a difference will ever be documented.
12/8/109245
doi:10.1067/mtc.2000.109245
References
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Engelman RM, Pleet AB, Hicks R, Rousou JA, Flack JE ed, Deaton DW, et al. Is there a relationship between systemic perfusion temperature during coronary artery bypass grafting and extent of intraoperative ischemic central nervous system injury? J Thorac Cardiovasc Surg 2000;119:230-2.[Abstract/Free Full Text]
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Gaudino M, Martinelli L, Di Lella G, Glieca F, Marano P, Schiavello R, et al. Superior extension of intraoperative brain damage in case of normothermic systemic perfusion during coronary artery bypass operations. J Thorac Cardiovasc Surg 1999;118:432-7.[Abstract/Free Full Text]
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Engelman RM, Pleet AB, Rousou JA, Flack JE 3rd, Deaton DW, Pekow PS, et al. The influence of CPB perfusion temperature on neurologic and hematologic function after coronary artery bypass grafting. Ann Thorac Surg 1999:67:1547-56.
