Blood Glucose and Neurologic Outcome

Rogers, Anne

Abstract

Following coronary artery bypass grafting (CABG), 2-5% of patients suffer transient or permanent stroke, 50-80% demonstrate decrements in psychomotor performance, 100% show evidence of intraoperative retinal vessel occlusion, and 50% show biochemical evidence of neurologic injury. Despite the individual and social costs of these injuries, several fundamental questions about the conduct of cardiopulmonary bypass (CPB) remain unanswered. One of these questions, that of control of spontaneous hyperglycemia to ischemic neurologic injury. Project 1 will consist of a randomized, controlled clinical trial that will combine postoperative outcome data, intraoperative physiologic data, and data quantitating preoperative, intraoperative, and postoperative risk factors to determine the influence of blood glucose (BG) control on the combined prevalence of new post-CABG neurologic, neuro-ophthalmologic, and neuropsychologic deficits. The primary question that this project will address is whether rigorous control of BG, compared to no BG control during hypothermic, non- pulsatile CPB reduces the combined prevalence of new deficits 5-7 days postoperatively. Spontaneous hyperglycemia during CPB is a frequent occurrence, resulting in marked elevation of BG in approximately 75% of non-diabetic patients. In current clinical practice, these BG elevations are not routinely treated in non-diabetic patients, while in diabetic patients, insulin therapy is directed at avoidance of extreme hyperglycemia and metabolic acidosis rather than strict maintenance of normoglycemia. In this project, patients in the treatment group will have strict control of BG to a target level of 100 mg/dl, while in the control group, BG levels will be allowed to fluctuate spontaneously. Since approximately 25% of patients will have mild hyperglycemia despite therapy with insulin infusion, a secondary analysis will address the influence of BG fluctuations, overall and within each treatment group, on postoperative outcome. The project will also address the influence of BG control and BG fluctuations on neurologic outcome at 6 months after discharge, and the length of postoperative hospital stay. Special attention will be paid to the outcome in two high-risk groups, patients with cerebrovascular disease (CVD) and those of advanced age.