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Ann Thorac Surg 2000;69:336
© 2000 The Society of Thoracic Surgeons
a Transplant Unit, Papworth Hospital, Cambridgeshire, England, United Kingdom
Address reprint requests to Dr Large, Transplant Unit, Papworth Hospital, Papworth Everhard, Cambridgeshire CB3 8RE, England
In the language of neuropsychologists, few words are quite as dirty as cardiopulmonary bypass (CPB). The brain dysfunction and cognitive decline associated with this awkward assortment of tubes, connections, and casings has long been a thorn in the side of cardiac surgery. In the mid 1980s, Shaw and associates [1] performed a landmark study prospectively analyzing 312 cardiac surgical patients with a battery of 10 standard tests of psychometric function preoperatively and then at 7 days and 6 months after surgery. At the time of hospital discharge, 79% of patients showed a significant decrement in their cognitive performance, and in 57%, there was intellectual dysfunction at 6 months. However, upon closer scrutiny, it became apparent that the situation was less clear-cut than previously imagined, and that perhaps the CPB machine was not the sole culprit. Of the 147 patients showing impairment at 6 months, 19 had no impairment at discharge, 43 patients were now impaired on a different test than previously, and only 3 patients had intellectual dysfunction that was incapacitating. In all three cases, the insult was a major perioperative stroke.
Fifteen years since the earliest studies on cognitive decline after CPB and we are still none the wiser as to its cause. Is it the pump? If so, surely by comparing patients having coronary artery bypass grafting (CABG) with and without CPB we may come to a conclusion. This theory was tested by Taggart and colleagues [2] through a prospective neuropsychological analysis of 50 patients undergoing conventional CABG and 25 patients undergoing CABG without CPB. Interestingly, they found no difference between the two groups preoperatively, at discharge, or at 3 months postoperatively using the same battery of 10 standard tests of neuropsychological function. To make things even more confusing, Murkin and associates [3] report the results of a similar study looking at 33 patients undergoing CABG with CPB and 35 patients having off-pump coronary revascularization (OPCAB). These patients were tested with a set of nine neuropsychological tests preoperatively and again at 5 days and 3 months postoperatively. In this study, OPCAB patients showed significantly less cognitive decline at 5 days (66% vs 90%) and at 3 months (5% vs 50%) compared with conventional CABG patients. So where do we stand now? Murkin’s team says it is the pump, Taggart’s team says it is more likely to be the general insult of surgery and the effects of anesthesia, and countless others have proposed different mechanisms of cerebral dysfunction. It is not difficult to imagine how so many conflicting messages exist in the face of dubiously designed and lamentably under-powered studies.
The problem of brain injury after cardiac surgery is a real one. Roach and associates [4] showed a 6.1% incidence of neurological injury in a large multicenter trial of 2,108 patients undergoing CABG. The uncertainty lies in what we as surgeons and anesthesiologists can do to avoid such complications. The answer is a large-scale multiinstitutional study comparing neuropsychological deficit between patients randomized to conventional CABG or OPCAB. Until such level A evidence is available, reduction of neuropsychological injury should not be viewed as an indication for OPCAB. Conventional CABG offers the benefit of excellent proven results, technical mastery, and access to multivessel disease. Calafiore and colleagues [5] report results of postoperative angiography in 176 patients who underwent off-pump grafting of the left internal mammary artery to the left anterior descending coronary artery. They show overall patency rates of 89.8% and perfect patency (<50% stenosis of grafted vessel) of 85.2%. These figures fall short of graft patency rates that can be achieved through conventional CABG. When combined with the fact that OPCAB has limited scope in revascularization of the posterolateral aspect of the heart, the use of OPCAB suddenly seems confined to a specific subgroup of individuals such as relatively young patients with disease confined to less than three vessels and good left ventricular function.
The November issue of the Annals featured Outcomes ’99, a supplement with a focus on neuropsychological injury after cardiac surgery. Numerous abstracts were presented and some valuable information was available, but unfortunately, Outcomes ’99 seems to fail at its very mission. If a conclusive outcome is the goal, all of the available literature must be used in a collaborative effort to plan a well-powered multicenter randomized control trial, ultimately leading to level A evidence for optimal neuroprotection. In the present state of affairs, the authors believe that until more definitive evidence is available, it would be morally questionable to undertake OPCAB outside the boundaries of such a study.
References
This article has been cited by other articles:
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  J. M. Murkin and D. A. Stump Res ipsa loquitur: protecting the brain in the new millennium, ""outcomes 2000"" Ann. Thorac. Surg., May 1, 2000; 69(5): 1317 - 1318. [Full Text] [PDF]
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