Respiratory gas exchange during robotic-assisted laparoscopic radical prostatectomy

Study Objective Robotic-assisted laparoscopic prostatectomy requires patients to be secured in a steep Trendelenburg position for several hours. Added to the CO₂ pneumoperitoneum that is created, this positioning invariably restricts diaphragmatic and chest wall excursion, which can adversely affect respiratory gas exchange. This study sought to measure the extent of respiratory gas change during this procedure. Design Retrospective, institutional review board approved. Setting Operating room. Patients N = 186 males, American Society of Anesthesiologists 2-3, with prostatic carcinoma undergoing robotic-assisted laparoscopic radical prostatectomy. Interventions Arterial blood gases and noninvasive respiratory measurements were recorded for those patients (n = 32) in whom a radial arterial catheter had been inserted intraoperatively, specifically timed to different phases of the procedure: supine lithotomy, steep Trendelenburg, and return to supine. Ventilatory parameters were standardized. Measurements Systemic blood pressure, heart rate, respiratory rate, Pao₂, Paco₂, oxygen saturation as measured by pulse oximetry, and end-tidal carbon dioxide pressure. Main Results Although no patients developed perioperative respiratory complications, the Pao₂ invariably fell (395 vs 316 mm Hg; P =.001) while the patients were in steep Trendelenburg, and the Paco₂-end-tidal carbon dioxide pressure rose (10.0 vs 13.4 mm Hg; P <.0001). Upon return to supine, patients' respiratory measurements promptly returned to within 15% of baseline. Subgroup analysis for high-BMI vs low-BMI patients as well as for patients with pulmonary disease and/or a smoking history showed similar individual effects and only small, although significant, respiratory gas exchange aberrations. Conclusions Positioning patients with a CO₂ pneumoperitoneum in steep Trendelenburg for several hours imposes restriction of diaphragmatic and chest wall movement sufficient for respiratory gas exchange to be adversely affected. Return of function to within 15% of baseline occurred within minutes after return to supine and release of the CO₂ pneumoperitoneum. No patients during the study period developed pulmonary complications that required alteration in their level of care.