Hemodynamic Effects of Steep Trendelenburg Position and Pneumoperitoneum in Urologic Robotic Surgery: a Prospective Study

Introduction Robot-assisted laparoscopic radical prostatectomy (RYLRP) is currently the most frequently performed surgical procedure using the Da Vinci Robotic System. In this procedure, the steep Trendelenburg position (30° - 45° head down) and pneumoperitoneum (insufflation of the intraabdominal space with CO2) are used to enhance surgical visibility in the retroperitoneal area. However, the patient position and pneumoperitoneum used in robotic surgery can lead to fluctuations in hemodynamic parameters resulting from physiological changes in the cardiovascular and respiratory systems. Consequently, proper hemodynamic monitoring and optimal fluid management can reduce the risk of complications and improve outcomes in patients.

Perfusion index (PI) is a hemodynamic parameter calculated by looking at the absorption of infrared light by pulse oximetry to evaluate continuous tissue perfusion for a specific time interval. In contrast, the Pleth variability index (PVI), a dynamic variable used for regulating fluid management, is computed based on changes in PI caused by ventilation over at least one respiratory cycle. Both parameters are key non-invasive methods for hemodynamic monitoring during patient follow-up as they provide accurate information about tissue perfusion. However, only a few studies have evaluated the effects of patient position and pneumoperitoneum on PI and PVI in laparoscopic surgeries. Therefore, this study aimed to prospectively investigate the effects of the steep Trendelenburg position and pneumoperitoneum on PVI and PI in patients scheduled for RYLRP under general anesthesia.

Materials and methods This prospective observational study was approved by the Ege University Faculty of Medicine Clinical Research Ethics Committee (approval number: E222840/280; dated July 7, 2021). Patients belonging to ASA classes I-II, aged between 25 and 80 years, and scheduled for elective RYLRP under general anesthesia were included in the study. Patients deemed suitable for the study were explained about the study, and written voluntary informed consent for participation was obtained. Two patients were eventually dropped from the study because of conversion to open surgery. Additionally, patients with an ASA score above III, those unsuitable for robotic surgery, and those who developed hemodynamic instability or respiratory complications during the intraoperative period were excluded.

Preanesthetic evaluations of the patients were performed at least 24 hour before the operation. Preoperative data, including age, weight, height, body mass index, ASA classification, and additional medical history, were recorded for each patient.

After being admitted to the operating room, standard monitoring (electrocardiogram, non-invasive blood pressure, peripheral oxygen saturation) was performed. In addition, non-invasive hemoglobin, PI, and PVI monitoring were conducted using a finger probe (Masimo Radikal 7, Masimo Corp., Irvine, CA, USA) which was placed on the fourth digit of the hand without the non-invasive blood pressure cuff. A 16-G or 18-G intravenous (IV) cannula was inserted, and an Isolyte-S infusion was initiated.