Peri-operative Monitoring of Cerebral Oxygenation and the Onset of Delirium in Patients Undergoing Cardiac Surgery

Delirium is an acute brain syndrome characterized by a disturbance in consciousness accompanied by periods of inattention and changes in cognition. Memory impairment, irrelevant speech and disorientation are commonly observed signs and symptoms. Episodes of delirium have been associated with a prolonged hospital stay, functional and cognitive dysfunction and even an increased mortality. Delirium is a common complication in the postoperative setting where the incidence increases with the risk of surgery. The estimated incidence of postoperative delirium after cardiovascular surgery is remarkable, ranging from 31% up to 51%. Diverse preoperative risk factors have been documented for patients undergoing cardiac surgery: age, pre-existing cognitive dysfunction, a history of alcohol abuse and the severity of illness at admission.

An early diagnosis of postoperative delirium is of great importance to prevent long-term cognitive impairment. For this purpose, a highly specific diagnostic monitoring tool should be implemented during perioperative cardiac surgery care. Near infrared spectroscopy (NIRS) provides information on brain oxygenation by quantifying the regional cerebral oxygen saturation (SctO2) at the microvascular level. Recently, two studies showed that preoperative cerebral tissue oxygenation was lower in the cohort of patients that developed delirium postoperatively. Nevertheless, these studies did not investigate whether the onset of postoperative delirium coincided with a change of postoperative SctO2. A relationship between delirium and reduced cerebral blood flow has already been suggested. As such, the occurrence of a postoperative decrease of SctO2 might have been overlooked thus far. Hence, Investigators want to conduct a prospective, interventional study to determine the relationship between postoperative SctO2 and the onset of delirium after cardiac surgery.