Individualized positive end-expiratory pressure titration on respiration and circulation in elderly patients undergoing spinal surgery in prone position under general anesthesia

Objective: To investigate the effect of individualized positive end-expiratory pressure (PEEP) titration on intraoperative respiration and circulation in elderly patients undergoing spinal surgery in prone position under general anesthesia. Methods: We prospectively selected 80 elderly patients (39 males and 41 females) aged over 65 years old, at American Society of Anesthesiologists (ASA) grade II or III, who underwent elective prone spinal surgery under general anesthesia, for this study. These patients were randomly divided into titration group and control group, with 40 cases in each group. PEEP of the titration group was increased from 0 to 20 cmH(2)O by steps of 2 cmH(2)O. For the control group, PEEP was constantly at 5 cmH(2)O and ventilation was maintained throughout the surgery. Dynamic pulmonary compliance (Cdyn) measurements were recorded when each PEEP level was kept for 1 min during titration, and individualized PEEP was determined by maximal Cdyn. MAP (mean arterial pressure), heart rate (HR), and CVP (Central venous pressure) were recorded at the set of prone position (T-0), PEEP ventilation for 10 min (T-1), 30 min (T-2), 60 min (T-3), end of surgery (T-4), and 20 min after extubation (T-5). Mean airway pressure (Pmean) and Cdyn were recorded from T-0 to T-4. Blood gas analysis was performed from T-0 to T-5 to calculate intrapulmonary shunt fraction (Qs/Qt) and OI (PaO(2/)FiO(2)). The rate of phenylephrine use during mechanical ventilation and the incidence of postoperative pulmonary complications were also recorded. Results: The individualized PEEP obtained by titration for 1 min in the titration group was (12.38 +/- 2.67) cmH(2)O, which was significantly higher than the 5 cmH(2)O in constant PEEP of the control group (P<0.05). There was no significant difference in MAP, HR, and CVP between the two groups at different time points, and no significant difference was noted in Pmean between the two groups from T-0 to T-4 (all P>0.05). From T-2 to T-4, Cdyn was significantly higher, and Qs/Qt was lower in the titration group than those in the control group (all P<0.05). From T-2 to T-5 , the OI in the titration group was significantly higher than that in the control group (P<0.05). The rate of phenylephrine use was significantly higher in the titration group than that in the control group (10 patients (25%) vs. 3 patients (8%), P<0.05). The incidence of postoperative pulmonary complications in the titration group was significantly lower than that in the control group (2 cases (5%) vs. 8 cases (20%), P<0.05). Conclusion: Compared with a constant PEEP of 5 cmH(2)O, intraoperative individualized PEEP titration in elderly patients undergoing spinal surgery in prone position can improve oxygenation, reduce intrapulmonary shunt and postoperative pulmonary complications.