Adverse Cerebral Outcomes After Coronary Bypass Surgery

ABSTRACT & COMMENTARY

Source: Roach GW, et al. N Engl J Med 1996;335:1857-1863.

A recent report re-emphasizes the not-always-understood principle that the central goal of applied medical care is to save or protect the brain. The authors represent outcomes of 2108 patients undergoing elective coronary bypass surgery carried out in 24 U.S. medical centers between September 1991 and September 1993. Four patients not included in the statistics died during surgery (why should they be excluded?), and another 305 were excluded because of confounding pre- or peri-operative conditions.

Severe cerebral impairment occurred in 129 patients (6.1%). Two types of complications of about equal total frequency contributed. Type I (n = 66) included post-operative fatal (n = 8) or not fatal (n = 55) stroke or hypoxic encephalopathy, TIAs (2), or stupor/coma (1) at discharge. Type II (n = 63) included "intellectual deterioration" encephalopathy (n = 55) and seizures (n = 8). Retrospectively analyzed principal risk factors for Type I included age over 70 years, the presence of proximal aortic atherosclerosis by surgical palpation or esophageal echograms, and a history of neurological and/or pulmonary disease. Type II risk factors included age over 70 years, previous CABG surgery, stroke, hypertension on admission, generalized atherosclerosis, pulmonary disease (smokers, emphysema, etc.), and alcoholism. Type I patients suffered substantially greater post-operative problems, as the above numbers indicate.

Neurological complications greatly increased medical costs. During hospitalizations, 14 of Type I patients died, and the others remained in the ICU for a mean of six days compared to 2.6 days in patients lacking neurological complications. Thus, the Type I patients had total mean hospitalizations amounting to 25 days compared to 9.5 in uncomplicated patients. Type II complicated patients did almost as badly, with 6.6 days in the ICU and total hospitalizations of 20.5 days. Only 21 (36%) of Type I survivors were discharged home (disabilities not identified). Also, 38 (60%) Type II patients went home, but only 90% of the total remaining patients were discharged home. Increased hospital costs for the brain-injured patients amounted to about $10,266 for each Type I patient and $6150 for each Type II. Post-hospitalization costs were not reported.

COMMENT BY FRED PLUM, MD

A disquieting observation appears in the report. By providing group averaging, the authors report data that might be taken to represent each of the 24 participating institutions. Rather, as the "Results" section indicates, the neurologically poor outcome rates among individual collaborators ranged from 1% to 13.8%, Type I outcomes being from 0 to 8.6% and Type II 0-9.3%. By their record, 10% of the non-neurologically injured patients also failed to return home. Why? No information indicates whether risk factors were similar in all participating institutions, whether pre- or post-operative evaluations included neurologists, and, especially, whether neurologists carefully studied the presurgical and outcome cognitive functions of all the patients to verify the complication statistics. The wide span of complication rates for different institutions raises the question of whether the selection of patients, surgical skill, and neurological evaluations were approximately the same in each institution. Furthermore, intellectual function cannot be adequately assessed without formal neurocognitive testing. Studies that have done this have identified significant persistent impairment in up to 35% of patients (Venn G, et al. Br Heart J 1987; 57:565). Without such information, it will be difficult to determine whether the already high neurological complication rate for coronary bypass surgery described by the authors accurately reflects the true neurological risk for CABG procedures. (Dr. Plum is Neurologist-in-Chief, New York Hospital, Cornell Medical Center.) v