Recovery of cerebral Perfusion and Mental function; A Comparison Between Normothermic and Hypothermic cardiopulmonary Bypass

Abstract

Central nervous system (CNS) complications continue to be a major cause of morbidity and mortality after cardiac surgery. Neuropsychological dysfunction after cardiopulmonary bypass (CPB) has been reported in as much as 79% of patients during the early postoperative period . Until recently, most cardiac surgical procedures that required cardiopulmonary bypass (CPB) were done in the presence of moderate systemic hypothermia (27° to 30° C). Hypothermia reduces tissue metabolic rate and oxygen demand and is used to assist in the protection of the myocardium and brain against potential ischemic insult. Because of reports of improved myocardial performance with warm cardioplegia and systemic normothermia, CPB with warm cardioplegia and systemic normothermia is being increasingly used nowadays. Patients undergoing normothermic bypass have a predictably higher cerebral oxygen demand and may be at higher risk for prolonged cerebral desaturation and ischemic injury than has been reported with hypothermic CPB. Jugular bulb saturation (SjVO,) indicate global balance of cerebral blood flow (CBF) and the cerebral metabolism (CMRO,) and it has been widely used to estimate the adequacy of flow/metabolism coupling in the brain during the peri-operative period and in the intensive care unit. During cardiac surgery, jugular venous desaturation has been noted

during several phases of normothermic and hypothermic CPB. We hypothesized that cerebral hypoperfusion may be occurring in the early postoperative period that can be identifiable by Sj02< 50%, and increased jugular bulb lactate concentration .