Cabbages and CABG.

Coronary artery bypass grafts relieve angina and prolong some patients' lives with an operative mortality of 1-4%. The grafting requires temporary artificial maintenance of the blood's circulation and oxygenation with cardiopulmonary bypass. In the United States some 200 000 people yearly have a coronary artery bypass graft-six times as many in relation to the population as in Britain. The greatest risk ofthe operation is to the brain, and the size of the risk has been explored by the superb prospective study of Pamela Shaw and her colleagues from Newcastle.'3 Other prospective studies have been published,45 and we now have a clearer picture of the risk of cerebral complications from cardiopulmonary bypass. The two most serious complications of cardiopulmonary bypass are diffuse encephalopathy from global cerebral anoxia and focal cerebral infarction. Shaw et al reported that 3% of their series of 312 patients had such a prolonged depression ofconsciousness, whereas 12% ofBreuer's 421 patients had an encephalopathy on the fourth day after the operation.4 Focal stroke occurred in about 5% of patients in both series and was described as severe in 2%. Patients may also suffer more subtle neuropsychological deficits after cardiopulmonary bypass, probably from patchy ischaemia in the cerebral arterial border zones. Four fifths of the patients in the Newcastle series showed deterioration in neuropsychological tests performed seven days after the operation compared with those performed before. Similarly, Smith et al found that two thirds of their patients showed neurophysiological impairment after seven days.5 But only about one third of the patients in both series had symptoms, and only 9% of the Newcastle patients were disabled from neurophysiological deficit. The patients' performance deteriorated in tests of psychomotor speed, perceptual attention, concentration, short term memory, new learning ability, and visuospatial organisation-tests that are sensitive to organic cerebral injury. Further evidence that cerebral damage occurs during cardiopulmonary bypass comes from Aberg et al, who correlated neurophysiological deficits with increases in adenylate kinase in cerebrospinal fluid, which were present in 91% of patients.6 How much of this cognitive carnage arises from cardio-pulmonary bypass and how much from other components of these large operations? Shaw et al found that a third of the 50 patients who had had large chest or vascular operations without cardiopulmonary bypass had neuropsychological deficit-but none had symptoms or were disabled. Smith's group, on the other hand, found that almost three fifths of the patients who had had large operations …