Cerebral tissue O2 saturation during prolonged robotic surgery in the steep Trendelenburg position: an observational case series in a diverse surgical population.

Demands associated with the Trendelenburg position (TP) are well known yet there is little attention given to regional cerebral tissue O2 saturation (SctO2) in those undergoing robotic surgery in the TP with CO2 insufflation (C-INSF). This is the first study to report on SctO2 in a wide range of patients undergoing lengthy TP and robotic surgery. We measured SctO2 during robotic surgery in patients in the TP with C-INSF, as well as a control robotic thyroid surgery group who were supine with no C-INSF. We recorded relevant variables and periods of cerebral desaturation (CD). We studied 42 patients in 25°-45° of TP for ≥125 min. Management was at the providers' discretion. The INVOS(®) 5100C Cerebral Oximeter (Covidien, Boulder, CO) recorded SctO2. CD was defined as a >20 % decrease from baseline SctO2 or a value ≤55 % for ≥10 min. Patients were assessed for adverse outcome. The sample consisted of 13 males and 29 females aged 22-73, BMI 22-36 had general (N = 3), urological (N = 14) and gynecological (N = 25) surgery; two patients had CD lasting 150 and 190 min and two had episodic CD lasting 10-35 min. The four were female aged 22-60 in 38°-45° of TP. Eleven cases had multiple episodic CD for ≤15 min, 27 TP cases had no CD. Other observations included a consistent fall in SctO2 with phenylephrine; an increased SctO2 with ephedrine; and FiO2 and EtCO2 being generally strong, direct modifiers of SctO2. High MAP was inconsistently associated with high SctO2. BMI had no observed effect on SctO2. Pulse oximetry was ≥97 % in all cases. We observed no adverse cerebral events on follow-up. Additional clinical studies are warranted.