Background: 

The Evaluation of Nitrous Oxide in the Gas Mixture for Anesthesia (ENIGMA)-I and ENIGMA-II were randomized clinical trials that assessed the safety of nitrous oxide anesthesia in patients undergoing noncardiac surgery. In this study, we performed an exploratory pooled analysis of both ENIGMA trials to assess the safety of nitrous oxide in a selected group of patients undergoing neurosurgery.

Methods: 

Data from each ENIGMA trial were collated into a single database. Information regarding patient demographics, comorbidities, medication use, anesthesia, surgical procedure, and postoperative complications was extracted. Multivariate logistic regression was conducted for postoperative complications to assess the risk associated with nitrous oxide.

Results: 

A total of 830 patients were included in our analysis: 417 received nitrous oxide anesthesia, and 413 received nitrous oxide-free anesthesia. Baseline patient and perioperative characteristics were comparable. Procedural data were available for 535 patients (64%); of these, 507 (95%) underwent spinal neurosurgery and 28 (5%) underwent cranial neurosurgery. Patients in the nitrous oxide group had lower inspired oxygen concentration (30% vs. 38%; P<0.001) and end-tidal volatile agent concentration (0.56 vs. 0.89 minimal alveolar concentration equivalents; P<0.001) compared with the nitrous oxide-free group. Use of nitrous oxide was not associated with increased risk of postoperative complications (myocardial infarction, cardiac arrest, stroke, infection, severe vomiting, fever, pneumonia, pneumothorax, blood transfusion, venous thromboembolism, or death) (odds ratio: 1.22; 95% confidence interval: 0.89-1.65; P=0.22) or prolonged length of hospital stay (median 5.0 vs. 4.2 d for nitrous oxide and nitrous oxide-free groups; P=0.28).

Conclusion: 

Nitrous oxide did not increase the risk of postoperative complications or prolonged length of hospital stay in the neurosurgical cohort enrolled in the ENIGMA-I and ENIGMA-II trials.

中文翻译：

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一氧化二氮麻醉在选定的神经外科患者组中的安全性：ENIGMA 试验的探索性亚组分析

背景： 

用于麻醉的气体混合物中的一氧化二氮评估 (ENIGMA)-I 和 ENIGMA-II 是随机临床试验，用于评估一氧化二氮麻醉在接受非心脏手术的患者中的安全性。在这项研究中，我们对两项 ENIGMA 试验进行了探索性汇总分析，以评估一氧化二氮在选定的接受神经外科手术的患者组中的安全性。

方法： 

每个 ENIGMA 试验的数据都被整理到一个数据库中。提取了有关患者人口统计学、合并症、药物使用、麻醉、外科手术和术后并发症的信息。对术后并发症进行多变量逻辑回归以评估与一氧化二氮相关的风险。

结果： 

我们的分析共包括 830 名患者：417 名接受一氧化二氮麻醉，413 名接受无一氧化二氮麻醉。基线患者和围手术期特征具有可比性。535 名患者 (64%) 的程序数据可用；其中，507 人（95%）接受了脊柱神经外科手术，28 人（5%）接受了颅神经外科手术。一氧化二氮组的患者吸入氧浓度较低（30% 对 38%；P <0.001）和呼气末挥发剂浓度（0.56 对 0.89 最小肺泡浓度当量；P<0.001) 与不含一氧化二氮的组相比。使用一氧化二氮与术后并发症（心肌梗死、心脏骤停、中风、感染、严重呕吐、发热、肺炎、气胸、输血、静脉血栓栓塞或死亡）风险增加无关（比值比：1.22；95%置信区间：0.89-1.65；P = 0.22）或延长住院时间（一氧化二氮和无一氧化二氮组的中位数为 5.0 对 4.2 天；P = 0.28）。

结论： 

在参加 ENIGMA-I 和 ENIGMA-II 试验的神经外科队列中，一氧化二氮不会增加术后并发症的风险或延长住院时间。