[Effect of open-lung ventilation strategy on oxygenation-impairment during laparoscopic colorectal cancer resection]

Objective: After general anesthesia and mechanical ventilation for laparoscopic colorectal cancer resection, about 90% of patients would have different degrees of atelectasis. Authors speculated that an open-lung strategy (OLS) comprising moderate positive end-expiratory pressure (PEEP) and intermittent recruitment maneuvers (RM) can reduce atelectrauma and thus reduce the incidence of oxygenation-impairment during low-tidal-volume ventilation for laparoscopic colorectal cancer resection. The purpose of this study was to verify this hypothesis and provide a better intraoperative ventilation scheme for laparoscopic colorectal cancer resection. Methods: This was a prospectively randomized controlled clinical trial which was approved by the Ethics Committee of the Sixth Affiliated Hospital, Sun Yat-sen University (2017ZSLYEC-002), and registered at the ClinicalTrials.gov (NCT03160144). From January to July 2017, patients who underwent laparoscopic colorectal cancer resection, with age > 40 years, estimated pneumoperitoneum time ≥ 1.5 h, pulse oxygen saturation ≥ 92%, and risk grade for postoperative pulmonary complications ≥ 2 were prospectively enrolled. The patients with American Society of Anesthesiologists physical status ≥ IV, body mass index ≥ 30 kg/m(2), pneumonia, acute respiratory failure or sepsis within 1 month, severe chronic obstructive pulmonary disease, pulmonary bullae and progressive neuromuscular diseases, and those participating in other interventional clinical trials were excluded. The enrolled patients were randomly assigned (1:1) to the OLS group (with a PEEP of 6-8 cm H(2)O and intermittent RM), and the NOLS group (without using PEEP and RM). Partial pressure of arterial oxygen (PaO(2)) /fraction of inspired oxygen (FiO(2)) and shunt fraction (Q(S)/Q(T)) were calculated via arterial and central venous blood gas analysis performed at 0.5 h (T(1)), 1.5 h (T(2)) after pneumoperitoneum induction and at 20 min after admission to the recovery room. Driving pressure immediately before pneumoperitoneum induction (T(0)) and at T(2) were calculated via monitoring data. The primary outcome was oxygenation-impairment (PaO(2)/FiO(2) ≤ 300 mmHg) during mechanical ventilation. Results: In each group, 48 patients under general anesthesia and low-tidal-volume ventilation were included in the final analysis. During ventilation, the oxygenation-impairment occurred in 7 patients (14.6%) of OLS group and in 17 patients (35.4%) of NOLS group, whose difference was statistically significant between two groups (χ(2)=5.556, RR=0.31, 95%CI: 0.12 to 0.84, P=0.033). During ventilation, the patients in the OLS group had higher PaO(2)/FiO(2) [T(1): (427±103) mmHg vs. (366±109) mmHg, t=-2.826, P=0.006; T(2): (453±103) mmHg vs. (388±122) mmHg, t=-2.739, P=0.007], lower Q(S)/Q(T) [ T(1): (9.2±6.5) % vs. (12.6±7.7) %, t=2.322, P=0.022; T(2): (7.0±5.8)% vs.(10.9±9.2)%, t=2.408, P=0.019], and lower driving pressure [T(0): (6±3) cm H(2)O vs. (10±2) cm H(2)O, t=7.421, P<0.001; T(2): (13±3) cm H(2)O vs. (17±4) cm H(2)O, t=5.417, P<0.001] than those in the NOLS group, with stratistical differences in all comparisons. In recovery room, though PaO(2)/FiO(2) [(70.3±9.4) mmHg vs. (66.8±9.4) mmHg, P=0.082] was still higher and Q(S)/Q(T) [(18.6±8.3)% vs. (21.8±8.4)%, P=0.070] was still lower in the OLS group as compared to the NOLS group, the differences were not statistically significant (both P>0.05). Conclusion: The application of such an OLS during low-tidal-volume ventilation can greatly reduce the incidence of oxygenation-impairment in laparoscopic colorectal cancer resection, and such effect may last to the period of emergence from anesthesia.