Effect of individualized PEEP on lung ultrasound score and optic nerve sheath diameter in elderly patients undergoing laparoscopic radical resection of rectal cancer A Randomized,Single blind, Prospective Study

Background : Intraoperative positive end-expiratory pressure (PEEP) has been promoted for many surgical procedures. However, whether PEEP has a dual protective effect on lung and brain is controversial,and the optimal PEEP associated with dual protection is unclear. The objective was to investigate the effects of individualized PEEP on lung ultrasound score (LUS) and optic nerve sheath diameter (ONSD) in elderly patients undergoing laparoscopic surgery. Methods : In total, 46 patients, aged 60～79 years, who underwent laparoscopic resection of rectal tumors from June 2022 to December 2022 were randomly divided into two groups:Groups E ( experimental group ,individualized PEEP guided by driving pressure) and Group C (control group ,PEEP = 5 cm H2O) . LUS was performed 30 min after operation. ONSD was measured at 5 min before anesthesia induction and various times post-surgery. The arterial oxygen index (OI) and arterial partial pressure of carbon dioxide (PaCO2) were recorded after tracheal tube insertion and before extubation at the end of the operation. Peak airway pressure (Ppeak), PETCO2, heart rate (HR), and mean arterial pressure (MAP) were also recorded. Postoperative pulmonary and neurological complications were followed up. Results : LUS in group E was significantly lower than that in group C at 30 min after surgery. The OI in group E was significantly higher than group C before extubation. There were no significant differences in the ONSD values between the two groups. ONSD of both groups increased significantly at 5 and 60 min after Trendelenburg positioning compared to before anesthesia induction. There were no significant differences between the two groups in Ppeak, PETCO2, HR, MAP at 5 min after tracheal tube insertion , no significant differences in the incidence of neurological and pulmonary complications . Conclusions : During laparoscopic radical resection of rectal cancer, application of individualized PEEP can reduce the LUS, improve patient oxygenation ,without causing an increase in neurological complications. Trial registration: This study was approved by the Ethics Committee of Chengdu Fifth People's Hospital, document number: AF/54/2020-02.3, approval number: 2022-026 (Study) -01. It has been registered on Chinese Clinical Trial Registry (ChiCTR2200060434,1/6/2022).