Adverse effects on the brain in cardiac operations as assessed by biochemical, psychometric, and radiologic methods

Abstract

In order to describe subclinical brain injury in conjunction with cardiac operations 94 patients were prospectively studied with three brain injury assessment methods: CSF analyses 24 hours after bypass, psychometry, and computed tomography of the brain. Adenylate kinase (AK), a marker of ischemic brain cell injury, was measured in cerebrospinal fluid (CSF) and in serum. In 13% of the patients, a considerable increase in CSF-AK was seen, in 46% there was a moderate increase, and in 41% no or trivial increase. Psychometry measured as change between preoperative scores in a test battery (SS3) revealed a moderate decrease in intellectual function after operation. There was a significant inverse correlation between CSF-AK and SS3 (r = -0.46, p less than 0.001, r2 = 0.21, n = 71). Computed tomography (CT) of the brain was performed preoperatively and postoperatively in 54 patients. Two of these had cerebral infarctions visible on the CT, despite an essentially normal postoperative state. There was no correlation between indices of brain injury and patient diagnosis and length of perfusion. It is concluded that subclinical brain injury is often seen after cardiac operations. Most often the injury appears trivial and/or reversible, but in a minority of cases there is evidence that the brain injury is irreversible. Factor analysis favors the view that the microembolism theory might no longer be a valid concept in modern cardiopulmonary bypass (CPB). Instead, circumstances in the operative field seem more likely to be important causative factors. This interpretation calls for new principles in the search for an improved cerebral protection during cardiac operations.