Individualised positive end-expiratory pressure guided by electrical impedance tomography for robot-assisted laparoscopic radical prostatectomy: a prospective, randomised controlled clinical trial

Abstract

Background: Robot-assisted laparoscopic radical prostatectomy requires general anaesthesia, extreme Trendelenburg positioning and capnoperitoneum. Together these promote impaired pulmonary gas exchange caused by atelectasis and may contribute to postoperative pulmonary complications. In morbidly obese patients, a recruitment manoeuvre (RM) followed by individualised PEEP improves intraoperative oxygenation and end-expiratory lung volume (EELV). We hypothesised that individualised PEEP with initial RM similarly improves intraoperative oxygenation and EELV in non-obese individuals undergoing robot-assisted prostatectomy.

Methods: Forty males (age, 49-76 yr; BMI <30 kg m^-2) undergoing prostatectomy received volume-controlled ventilation (tidal volume 8 ml kg^-1 predicted body weight). Participants were randomised to either (1) RM followed by individualised PEEP (RM/PEEP_IND) optimised using electrical impedance tomography or (2) no RM with 5 cm H₂O PEEP. The primary outcome was the ratio of arterial oxygen partial pressure to fractional inspired oxygen (Pao₂/F_io₂) before the last RM before extubation. Secondary outcomes included regional ventilation distribution and EELV which were measured before, during, and after anaesthesia. The cardiovascular effects of RM/PEEP_IND were also assessed.

Results: In 20 males randomised to RM/PEEP_IND, the median PEEP_IND was 14 cm H₂O [inter-quartile range, 8-20]. The Pao₂/F_io₂ was 10.0 kPa higher with RM/PEEP_IND before extubation (95% confidence interval [CI], 2.6-17.3 kPa; P=0.001). RM/PEEP_IND increased end-expiratory lung volume by 1.49 L (95% CI, 1.09-1.89 L; P<0.001). RM/PEEP_IND also improved the regional ventilation of dependent lung regions. Vasopressor and fluid therapy was similar between groups, although 13 patients randomised to RM/PEEP_IND required pharmacological therapy for bradycardia.

Conclusion: In non-obese males, an individualised ventilation strategy improved intraoperative oxygenation, which was associated with higher end-expiratory lung volumes during robot-assisted laparoscopic prostatectomy.

Clinical trial registration: DRKS00004199 (German clinical trials registry).

Keywords: electrical impedance tomography; minimally invasive surgery; positive pressure ventilation; pulmonary gas exchange; radical prostatectomy.