Ann Thorac Surg 2002;74:2160
© 2002 The Society of Thoracic Surgeons
Invited commentary
Paul W.M. Fedak, MDa,
Nick Mamalias, MSa,
Richard D. Weisel, MDa
a Toronto General Hospital, Division of Cardiac Surgery, 200 Elizabeth Street EN 14-215 Toronto, Ontario M5G 2C4 Canada
Falcoz and colleagues performed a prospective randomized trial evaluating myocardial protection in patients undergoing primary elective coronary bypass surgery. They found no difference between warm and tepid blood cardioplegia. In these low-risk patients, both types of cardioplegia provided excellent protection. A larger study for the inclusion of high-risk patients would be required to distinguish between the two techniques. In our evaluation of warm cardioplegia, we became concerned that some patients may suffer warm ischemic injury when cardioplegia could not be delivered homogeneously and continuously. Therefore, warm cardioplegia is not employed at the University of Toronto. Tepid heart surgery provides some degree of protection when cardioplegic delivery is inadequate. However, slight cooling of the heart preserves cardiac metabolic activity and permits early resumption of cardiac function.
The major concern with warm heart surgery is the risk of neurologic events if the brain is not cooled [1]. Maintaining a normothermic body temperature requires active heating of the blood which may overheat the brain, exacerbating any neurologic injury occurring during cardiopulmonary bypass[2]. Therefore, we advocate permitting the systemic temperature to "drift". Both active cooling and warming may be detrimental to the systemic circulation. Allowing the systemic temperature to drift provides mild cooling, and slow rewarming can avoid overheating the brain.
The best protection of the heart may be accomplished with a "tepid" temperature. However, a large randomized trial incorporating high-risk patients would be required to demonstrate a difference. We believe that systemic temperatures should not be maintained at normothermia to avoid neurologic injury.
References
- Craver J.M., Bufkin B.L., Weintraub W.S., Guyton R.A. Neurologic events after coronary bypass grafting: further observations with warm cardioplegia. Ann Thorac Surg 1995;59:1429-1433.[Abstract/Free Full Text]
- Borger M.A., Ivanov J., Weisel R.D., Rao V., Peniston C.M. Stroke during coronary bypass surgery: principal role of cerebral macroemboli. Eur J Cardiothorac Surg 2001;19:627-632.[Abstract/Free Full Text]
