J Thorac Cardiovasc Surg 1998;115:483-484
© 1998 Mosby, Inc.
Temperature during cardiopulmonary bypass for coronary artery operations does not influence postoperative cognitive function: A prospective, randomized trial
Gilles Plourde, MD,
Benoît de Varennes, MD,
Jean E. Morin, MD
Reply to the Editor:
We thank Ündar and associates for their interest, However, we still see no evidence that membrane oxygenators improve cognitive outcome. Of the eleven references cited, only the preliminary report by Blauth and associates
1 compared bubble and membrane oxygenators with regard to postoperative cognitive function. This study revealed a small, nonsignificant difference in favor of the membrane oxygenator. The number of patients with postoperative neuropsychologic impairment was 17 of 22 (77%) in the bubble group and eight of 12 (67%) in the membrane group (p = 0.50, 
2 done by us). The mean number of neuropsychologic tests (n = 10) showing postoperative deterioration was 1.24 in the bubble group and 0.91 in the membrane group (p < 0.11, Mann-Whitney U test, reported by Blauth's group).
We agree with Ündar and associates that cerebral emboli play a role in postoperative neuropsychologic dysfunction and that the number of microemboli during cardiopulmonary bypass is less with membrane than with bubble oxygenators. Whether this difference would persist with a 20 µm in-line arterial filter (used in our study) is not known.
Our practice is to use bubble oxygenators for uncomplicated cases and membrane oxygenators for complex cases. This decision was taken by the cardiac surgeons of the Royal Victoria Hospital. It was not dictated by hospital administrators. We think that this approach makes optimal use of available resources. We believe that the systematic use of alternative, more expensive equipment in the absence of demonstrated improvement in outcome should be avoided.
Departments of Anaesthesia and SurgeryRoyal Victoria HospitalMontreal, Quebec H3A 1A1, Canada
References
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Blauth C, Smith P, Newman S, et al. Retinal microembolism and neuropsychological deficit following clinical cardiopulmonary bypass: comparison of a membrane and a bubble oxygenator—a preliminary communication. Eur J Cardiothorac Surg 1989;3:135-9.[Abstract]
