We read with great interest the systematic review by Meewisse et al. on the effect of time of day on outcomes in elective surgery [1]. They postulate that timing of elective surgery could affect clinical outcome due to diurnal rhythms of patient physiology as well as surgical team performance. They found that evening/night-time elective surgery is associated with a higher risk of mortality compared with daytime surgery. While this seems intuitive, it is a topic lacking robust evidence at present.

With wait times for elective surgeries rising worldwide, as well as an ageing and increasingly more medically complex population, concerns surrounding patient safety with out-of-hours elective surgeries are high. This issue is of particular relevance in standalone obstetrics and gynaecology hospitals like ours, The National Maternity Hospital in Dublin, where elective surgeries are sometimes postponed to the evening due to emergency obstetric procedures occurring throughout the day. While the proportion of elective work in our hospital undertaken out-of-hours is low (approximately 1%), it is a common theme in obstetric hospitals.

The recently published 7th National Audit Project (NAP7) noted that, regarding elective surgeries, gynaecology was one of the most overrepresented surgical specialities with incidences of potentially serious complications and peri-operative cardiac arrest [2].

Meewisse et al. suggest ‘surgeon fatigue’ as a potential cause of increased morbidity/mortality with evening and night-time elective surgery [1]. However, we believe that fatigue affecting the entire operating theatre team is a more accurate risk factor. This coupled with reduced staffing levels and a lack of consultant anaesthetist presence that is commonplace in the evening and at night, may additionally contribute to increased out-of-hours morbidity and mortality. In fact, the NAP7 report mentions this point.

Additionally, adverse airway incidents leading to cardiac arrest in NAP7 were found to occur disproportionately out of hours, with 36% taking place at weekends, or in the evening or night-time hours [2]. While most elective caesarean section procedures are facilitated with neuraxial anaesthesia, it is estimated that a difficult airway is eight times more likely to be encountered in a pregnant than non-pregnant patient, should a general anaesthetic be necessary [3].

We were particularly interested to read about the diurnal variation in platelets and clotting factor activation and how this could be applied to improve patient outcomes. This is of particular relevance to our obstetrics and gynaecology specialist hospital which is the national referral centre for placenta accreta spectrum in Ireland. Perhaps in the future we will see more customised timing of surgical procedures with higher bleeding risks.

Meewisse et al. acknowledge that the quality of evidence included in their systematic review is low, but recent findings from NAP7 would support their theory that outcomes in out-of-hour surgeries are worse.

We agree that further investigation of this topic in the form of a well-designed, prospective study may provide a better understanding of the influence of timing of elective surgery on postoperative outcomes. This is an important topic that will provide clarity surrounding this issue in healthcare systems struggling with capacity and inadequate staffing levels. We see this as a modifiable risk factor which can and should be addressed.

我们怀着极大的兴趣阅读了 Meewisse 等人关于一天中的时间对择期手术结果影响的系统评价 [1]。他们假设择期手术的时间可能会影响临床结果，因为患者生理的昼夜节律以及手术团队的表现。他们发现，与日间手术相比，夜间/夜间择期手术与更高的死亡风险相关。虽然这看起来很直观，但目前这是一个缺乏有力证据的话题。

随着全球择期手术等待时间的增加，以及人口老龄化和医疗复杂性日益增加，人们对非工作时间择期手术的患者安全高度担忧。这个问题在独立的妇产科医院中尤为重要，比如我们都柏林的国家妇产医院，由于全天都在进行紧急产科手术，择期手术有时会推迟到晚上。虽然我们医院在非工作时间进行的选择性工作比例很低（约 1%），但这是产科医院的共同主题。

最近发布的第 7 个国家审计项目 （NAP7） 指出，就择期手术而言，妇科是代表性最强的外科专业之一，发生率可能很高的严重并发症和围手术期心脏骤停 [2]。

Meewisse 等人认为，“外科医生疲劳”是夜间和夜间择期手术并发症发生率/死亡率增加的潜在原因 [1]。然而，我们认为影响整个手术室团队的疲劳是一个更准确的风险因素。再加上人员配备水平的减少和缺乏顾问麻醉师在场（这在晚上和晚上很常见），可能还会导致非工作时间发病率和死亡率的增加。事实上，NAP7 报告提到了这一点。

此外，研究发现，导致 NAP7 心脏骤停的不良气道事件不成比例地发生在工作时间之外，其中 36% 发生在周末、晚上或夜间 [2]。虽然大多数选择性剖宫产手术都通过椎管内麻醉来促进，但据估计，如果需要全身麻醉，妊娠患者遇到困难气道的可能性是非妊娠患者的 8 倍 [3]。

我们特别感兴趣的是了解血小板和凝血因子激活的昼夜变化，以及如何将其应用于改善患者预后。这与我们的妇产科专科医院特别相关，该医院是爱尔兰侵入性胎盘谱系的国家转诊中心。也许在未来，我们将看到更多定制化的手术时间，出血风险更高。

Meewisse 等人承认，他们的系统评价中包含的证据质量很低，但 NAP7 的最新发现将支持他们的理论，即非工作时间手术的结果更差。

我们同意，以精心设计的前瞻性研究的形式对这一主题进行进一步调查可能会更好地了解择期手术时间对术后结局的影响。这是一个重要的话题，它将在与容量和人员配备水平不足作斗争的医疗保健系统中明确这个问题。我们认为这是一个可以改变的风险因素，可以而且应该得到解决。