We thank Chen et al. [1] for their interest in our study [2], in which we found that opioid-free versus opioid-inclusive propofol anaesthesia reduced the incidence of postoperative nausea and vomiting (PONV) during the first 48-h postoperatively (5% vs. 24%; odds ratio 0.17, 95%CI 0.08–0.35; number needed to treat 5.3; p < 0.001). Opioid-free anaesthesia was also associated with a reduced need for rescue anti-emetics, lower incidences of hypotension and oxygen desaturation after tracheal extubation, and improved patient satisfaction.

Chen et al. suggest that nausea, retching and vomiting episodes should be documented and analysed separately. We defined PONV as a composite outcome including any episodes of nausea, retching or vomiting based on the literature [3]. This definition was also used in our recent study conducted in patients undergoing thoracoscopic lung surgery [4]. Few studies specified an individual occurrence of nausea, retching or vomiting as the primary outcome. We did not report the individual occurrences of PONV in our patients; however, among the secondary outcomes, the reduced PONV severity and need for rescue anti-emetics suggests that opioid-free anaesthesia alleviated PONV in patients undergoing thyroid and parathyroid surgery.

To assess the severity of PONV, we applied the PONV impact scale [3]. For opioid-free versus opioid-inclusive anaesthesia, the incidences of mild, moderate and severe PONV episodes were 5% versus 16% (p < 0.001), 1% versus 4% (p = 0.037) and 0% versus 3% (p = 0.030), respectively. The between-group differences were all statistically significant before multiple comparison corrections. In a post hoc analysis of combining moderate and severe PONV categories, we found a reduced incidence of moderate-to-severe PONV (1% vs. 7%, p < 0.001) in the opioid-free group, which remains significant even after correction for multiple comparison. Based on these data, we respectfully disagree that opioid-free propofol anaesthesia reduced only mild PONV in our patients. Moreover, we showed that patient satisfaction was higher in the opioid-free group. It is clinically meaningful that opioid-free anaesthesia improved patient comfort after thyroid and parathyroid surgery.

In terms of adverse effects, the incidence of nightmares or hallucination was 4% in the opioid-free group versus 2% in the opioid-inclusive group (odds ratio 1.78, 95%CI 0.56–5.50, p = 0.617), without a significant between-group difference. We cannot assume that more patients in the opioid-free group would experience nightmares or hallucinations. The tracheal extubation time was slightly longer (median 5 min) in the opioid-free group, while the duration of post-anaesthesia care unit stay was comparable between groups. The median dose of intra-operative propofol was 740 mg and 690 mg in the opioid-free group and opioid-inclusive group, respectively. This is a clinically insignificant difference. Hence, these results suggested that opioid-free propofol anaesthesia did not prolong recovery or increase resource utilisation in our patients. The median dose of sufentanil used in the opioid-inclusive group was 40 μg (approximately 0.6 μg.kg^-1) as per our clinical practice. This provides sufficient analgesia and is in line with doses reported in the literature [5, 6].

我们感谢 Chen 等人 [1] 对我们的研究 [2] 的兴趣，在该研究中，我们发现无阿片类药物与包含阿片类药物的异丙酚麻醉降低了术后前 48 小时内术后恶心和呕吐 （PONV） 的发生率 （5% vs. 24%;比值比 0.17,95%CI 0.08-0.35;需要治疗的人数 5.3;p < 0.001）。无阿片类药物麻醉还与减少对抢救止吐药的需求、降低气管拔管后低血压和氧饱和度下降的发生率以及提高患者满意度有关。

Chen 等人建议应分别记录和分析恶心、干呕和呕吐发作。根据文献，我们将 PONV 定义为复合结局，包括任何恶心、干呕或呕吐的发作 [3]。我们最近对接受胸腔镜肺部手术的患者进行的研究中也使用了这个定义 [4]。很少有研究将恶心、干呕或呕吐的个体发生作为主要结局。我们没有报告患者 PONV 的个体发生率;然而，在次要结局中，PONV 严重程度降低和需要抢救止吐药表明，无阿片类药物麻醉缓解了接受甲状腺和甲状旁腺手术的患者的 PONV。

为了评估 PONV 的严重程度，我们应用了 PONV 影响量表 [3]。对于无阿片类药物与阿片类药物联合麻醉，轻度、中度和重度 PONV 发作的发生率分别为 5% 对 16% （p < 0.001）、1% 对 4% （p = 0.037） 和 0% 对 3% （p = 0.030）。在多次比较校正之前，组间差异均具有统计学意义。在结合中度和重度 PONV 类别的事后分析中，我们发现无阿片类药物组中度至重度 PONV 的发生率降低 （1% vs. 7%，p < 0.001），即使在校正多重比较后，这种情况仍然显着。基于这些数据，我们尊重地不同意不含阿片类药物的异丙酚麻醉仅降低了我们患者的轻度 PONV。此外，我们发现无阿片类药物组的患者满意度更高。无阿片类药物麻醉改善了甲状腺和甲状旁腺手术后患者的舒适度，具有临床意义。

在不良反应方面，无阿片类药物组的噩梦或幻觉发生率为 4%，而阿片类药物组为 2%（比值比 1.78,95%CI 0.56-5.50，p = 0.617），组间无显著差异。我们不能假设无阿片类药物组中有更多的患者会经历噩梦或幻觉。无阿片类药物组的气管拔管时间略长 （中位数 5 min），而两组之间麻醉后监护病房的停留时间相当。无阿片类药物组和阿片类药物包涵组术中异丙酚的中位剂量分别为 740 mg 和 690 mg。这是一个临床上不显著的差异。因此，这些结果表明，不含阿片类药物的异丙酚麻醉不会延长我们患者的恢复时间或增加资源利用率。根据我们的临床实践，阿片类药物组使用的舒芬太尼的中位剂量为 40 μg（约 0.6 μ ^g.kg-1）。这提供了足够的镇痛作用，并且与文献中报道的剂量一致 [5， 6]。