Correlation between Cerebral Oxygenation and Mean Arterial Pressure during Shoulder Artroscopic Surgeries in the Beach Chair Position under General Anaesthesia

Aim: To determine the relationship between near-infrared spectroscopy (NIRS) and patient’s hemodynamic parameters during shoulder surgery. Objectives: 1. To evaluate the correlation between near-infrared spectroscopy (NIRS) and mean arterial pressure (MAP) at different levels of controlled hypotension. 2. To evaluate the correlation between near-infrared spectroscopy (NIRS) and oxygen saturation (SpO2). 3. To evaluate the correlation between near-infrared spectroscopy (NIRS) and end–tidal carbon dioxide (EtCO2). 4. To evaluate the frequency of cerebral desaturation episodes in the beach chair position. Methods and participants: The study was performed at Hospital of LUHS Kaunas Klinikos Orthopaedics - Traumatology Clinic with the approval of the Bioethics Centre. The study included 40 patients who underwent elective shoulder arthroscopic surgery without concomitant diseases and other exclusion criteria. All patients were divided into 2 groups where the mean arterial pressure (MAP) was maintained between 50 and 60 mmHg (1st group) and 60 to 70 mmHg (2nd group) during surgery. All patients were prepared for surgery according to a standard protocol, and NIRS-detecting sensors in the forehead area were connected. All patients underwent interscalene plexus brachialis blockage and general anaesthesia. MAP, NIRS, EtCO2, and SpO2 were recorded in 12 stages throughout the operation. The statistical package SPSS 21.0 for Windows and non-parametric criteria were used to calculate the data. Results: The study included 40 patients, with 20 patients in each group. It was found that although MAP values were maintained differently, NIRS values did not differ between the two groups, and MAP and NIRS correlated with each other. No strong correlation was observed between SpO2 and NIRS, but NIRS values were also observed to increase with increasing EtCO2. Episodes of cerebral desaturation were corrected by ephedrine in 7 of 40 patients (4 cases (20%) in group 1, 3 cases (15%) in group 2). Conclusions: 1. At different levels of controlled hypotension, the values of NIRS did not differ, although they correlated with each other, so it can be argued that NIRS is a sufficiently sensitive method to reflect regional cerebral blood flow. 2. No statistically significant correlation was observed between SpO2 and cerebral oxygenation, and therefore brain perfusion cannot be assessed by pulse oximetry. 3. A correlation has been observed between EtCO2 and NIRS, so it can be argued that increasing EtCO2 can improve brain perfusion. 4. Some patients have experienced episodes of desaturation during surgery, so intensive follow-up of patients is an unavoidable part of treatment