Assessment of cerebral oxygenation changes of obese patients, during bariatric surgery at different positions

Purpose: Obesity is a chronic disease affecting the quality of life and duration in a negative way and obesity-oriented operations are a very effective method of ensuring the continuity of weight loss in morbidly obese patients. In anesthetized patients, there are significant effects on pulmonary mechanics and perfusion due to the gravity of position changes. It is also known that PEEP application has positive effects on the respiratory system with different mechanisms. In this prospective, observational study, we aimed to compare cerebral oxygenation levels in varying positions when 5 cmH2O PEEP and 10 cmH2O PEEP were administered to obese patients undergoing bariatric surgery. Materials and Methods: This study included 50 patients who underwent laparoscopic bariatric surgery between December 2015 and June 2016 at İnönü University Faculty of Medicine at ASA physical class II, aged 18-50 years, BMI>35 years. Patients were divided into two groups to receive 5 cmH2O PEEP (Group 1, n=25) and 10 cmH2O PEEP (Group 2, n=25). In addition to routine monitoring, regional cerebral oxygen saturation (rSO2) monitoring was performed with a two-sensor cerebral oximeter. Cerebral oxygen values and hemodynamic parameters were recorded before induction of anesthesia in the supine position of the patients. rSO2 values and hemodynamic parameters before and after CO2 insufflation (5 min), after the reverse trendelenburg position, after the trendelenburg position, after deflation (5 min) and after extubation (5 min), were recorded. Results: There was no statistically significant difference between the groups, with the rSO2 left levels at all times being measured resembling in group 1 and group 2. Group 1 baseline values (T0) were compared within the group; The measurements at T1, T5, T6, T7 were considered statistically significant (p <0.05). In group 2, in-group comparison according to basal values (T0); The measurements at T1, T3, T5, T6, T7, T8 were considered statistically significant (p<0.05). There was no significant difference in the statistical analysis of the values obtained in groups 1 and 2 between the groups. Group 1 baseline values (T0) were compared within the group; the measurements at T1, T5, T6, T7 were considered statistically significant (p<0.05). In group 2, in group comparison according to basal values (T0); the measurements at T1, T3, T5, T6, T7, T8 were considered statistically significant (p<0.05). In both groups, there was no statistical difference in the comparison of the values between the rSO2 left and rSO2 right sensors (T1, T5, T6, T7) compared with baseline values (T1, T5, T6, T7). Conclusion: The application of 5 cmH2O and 10 cmH2O PEEP in changing positions in morbidly obese patients undergoing laparoscopic bariatric surgery not only protects respiratory mechanics and arterial oxygenation but also maintains rSO2 without hemodynamic instability. Further clinical investigations using innovative technological tools or updated versions of available tools will enable closer monitoring of the resulting intraoperative physiopathological haemodynamic changes. Keywords: Obesity, bariatric surgery, Positive end-expiratory pressure, cerebral oximeter, near-infrared spectroscopy