Department of Anaesthesia, Austin Health, Heidelberg, Victoria, Australia; and the Department of Critical Care, Melbourne Medical School, University of Melbourne, Melbourne, Victoria, Australia.
Department of Anaesthesia, Austin Health, Heidelberg, Victoria, Australia.
Anesthesiology. 2023 Apr 1;138(4):354-363. doi: 10.1097/ALN.0000000000004497.
Nitrous oxide promotes absorption atelectasis in poorly ventilated lung segments at high inspired concentrations. The Evaluation of Nitrous oxide In the Gas Mixture for Anesthesia (ENIGMA) trial found a higher incidence of postoperative pulmonary complications and wound sepsis with nitrous oxide anesthesia in major surgery compared to a fraction of inspired oxygen of 0.8 without nitrous oxide. The larger ENIGMA II trial randomized patients to nitrous oxide or air at a fraction of inspired oxygen of 0.3 but found no effect on wound infection or sepsis. However, postoperative pulmonary complications were not measured. In the current study, post hoc data were collected to determine whether atelectasis and pneumonia incidences were higher with nitrous oxide in patients who were recruited to the Australian cohort of ENIGMA II.
Digital health records of patients who participated in the trial at 10 Australian hospitals were examined blinded to trial treatment allocation. The primary endpoint was the incidence of atelectasis, defined as lung atelectasis or collapse reported on chest radiology. Pneumonia, as a secondary endpoint, required a diagnostic chest radiology report with fever, leukocytosis, or positive sputum culture. Comparison of the nitrous oxide and nitrous oxide-free groups was done according to intention to treat using chi-square tests.
Data from 2,328 randomized patients were included in the final data set. The two treatment groups were similar in surgical type and duration, risk factors, and perioperative management recorded for ENIGMA II. There was a 19.3% lower incidence of atelectasis with nitrous oxide (171 of 1,169 [14.6%] vs. 210 of 1,159 [18.1%]; odds ratio, 0.77; 95% CI, 0.62 to 0.97; P = 0.023). There was no difference in pneumonia incidence (60 of 1,169 [5.1%] vs. 52 of 1159 [4.5%]; odds ratio, 1.15; 95% CI, 0.77 to 1.72; P = 0.467) or combined pulmonary complications (odds ratio, 0.84; 95% CI, 0.69 to 1.03; P = 0.093).
In contrast to the earlier ENIGMA trial, nitrous oxide anesthesia in the ENIGMA II trial was associated with a lower incidence of lung atelectasis, but not pneumonia, after major surgery.
氧化亚氮在高吸入浓度下可促进通气不良肺段的吸收性肺不张。氮氧化合物在麻醉中的评价（ENIGMA）试验发现，与不使用氧化亚氮的 0.8 分率吸入氧相比，在大手术中，氧化亚氮麻醉后术后肺部并发症和伤口败血症的发生率更高。更大规模的 ENIGMA II 试验将患者随机分配到氧化亚氮或空气组，吸入氧分数为 0.3，但未发现对伤口感染或败血症有影响。然而，并未测量术后肺部并发症。在本研究中，事后数据收集旨在确定在澳大利亚 ENIGMA II 队列中招募的患者中，氧化亚氮是否会导致更高的肺不张和肺炎发生率。
对参加澳大利亚 10 家医院试验的患者的数字健康记录进行了检查，检查时对试验治疗分配进行了盲法。主要终点是肺不张的发生率，定义为胸部放射影像学报告的肺不张或塌陷。肺炎作为次要终点，需要有诊断性胸部放射影像学报告，伴有发热、白细胞增多或痰培养阳性。根据意向治疗，使用卡方检验比较氧化亚氮组和无氧化亚氮组。
最终数据集包括 2328 名随机患者的数据。两组的手术类型和持续时间、ENIGMA II 记录的危险因素和围手术期管理相似。氧化亚氮组肺不张发生率降低 19.3%（171/1169[14.6%] vs. 210/1159[18.1%]；比值比，0.77；95%CI，0.62 至 0.97；P=0.023）。肺炎发生率无差异（1169 例中有 60 例[5.1%] vs. 1159 例中有 52 例[4.5%]；比值比，1.15；95%CI，0.77 至 1.72；P=0.467）或联合肺部并发症（比值比，0.84；95%CI，0.69 至 1.03；P=0.093）。
与早期的 ENIGMA 试验相比，ENIGMA II 试验中的氧化亚氮麻醉与大手术后肺不张发生率降低相关，但与肺炎发生率无关。
