Regional Cerebral Oxygen Saturation Under General Anesthesia A Pilot Study

Overview

A total of 60 patients will be enrolled in the study: 20 each who receive surgery in beach chair position or Trendelenburg's position and 20 patients undergoing cardiac surgery. Regional cerebral oxygen saturation will be measured continuously during surgery. Duration and extent of deviations from individual baseline values will be recorded and detected deviations treated according to their clinically apparent cause (e.g. hypotension/hypovolaemia, anaemia, low cardiac output) in accordance with our standard operating procedures (SOPs). Patients are then followed up until the end of hospital stay or for a maximum of 10 days after surgery. Their level of cognitive function will be tested and compared to the data acquired before surgery to detect impairment, delirium or postoperative cognitive deficit (POCD). The purpose of this pilot study is to evaluate the design and conduct of a projected full scale observational clinical study.

The primary goal of this study is the detection of perioperative fluctuations of regional cerebral oxygen saturation in patients undergoing surgery in general anaesthesia. These fluctuations will be monitored using the a non-invasive monitoring system based on the method of near-infrared spectroscopy (NIRS). Regional cerebral hypoxia is considered one of the possible precipitating factors of postsurgical cognitive impairment (as seen in patients with postoperative cognitive deficit or postoperative delirium), but without monitoring it may easily remain undetected. A differentiated analysis of fluctuations is gained by calculation of the area under curve (AUC) of a defined deviation from individual baseline regional cerebral oxygen saturation (rSO2) over time. When deviations are detected, they will be treated in this study according to their clinically apparent cause (e.g. hypotension/hypovolaemia, anaemia, low cardiac output) in accordance with current standard operating procedures (SOPs) to re-elevate regional cerebral oxygen saturation (rSO2) to within 20% of baseline. Among these procedures are 1. Elevation of systemic arterial pressure by application of vasopressors 2. Consideration of systemic (pulse oxymetric) oxygen saturation 3. Adjustment of artificial ventilation subject to endexpiratory concentration of carbon dioxide (CO2) 4. Transfusion of concentrated red cells in case of Hemoglobin (Hb) \<7-9 g/dl 5. Transthoracic or transesophageal echocardiogram (TTE/TEE) and assessment of centralvenous oxygen saturation in case of suspected myocardial insufficiency which should be applied to patients of the 3 defined groups as needed. This explorative project is a pilot study.