Prolonged motor block regression following neuraxial anaesthesia should prompt careful evaluation for serious postpartum neurological injuries and complications such as vertebral column haematoma. The ability to perform straight leg raise against gravity 4 h after neuraxial anaesthesia has been recommended as a time threshold to trigger review [1]. However, using this time threshold, we observed a large number of our patients required review, resulting in a labour-intensive process that we found difficult to sustain [2]. One possible explanation for the excessive number of triggers may be related to the increased local anaesthetic doses used at our institution, a practice that began during the COVID-19 pandemic and has continued. We hypothesised that the median time to motor block regression after spinal or epidural anaesthesia is > 4 h. To test this, we conducted a retrospective cohort study to characterise the duration of sensory and motor block regression following neuraxial anaesthesia for caesarean delivery (Fig. 1).

The study was deemed a quality improvement project and research ethics committee approval was not required. Data from 200 patients receiving intrathecal (n = 100, 0.75% hyperbaric bupivacaine with fentanyl 10–15 mcg and morphine 100 mcg) and epidural (n = 100, lidocaine 2% with adrenaline 1:200,000, fentanyl 50–100 mcg and morphine 1.5–2 mg) anaesthesia for elective or emergency caesarean deliveries were retrospectively collected from patient records between December 2021 and February 2022. Sensory and motor evaluations were performed as per our standard institutional protocol. The primary outcome was median time to motor block regression, defined as time of intrathecal injection or epidural top-up, to time of recovery of straight leg raising, analysed using Kaplan–Meier curves with hazard ratio obtained via the Mantel–Haenszel method. Secondary outcomes were median time to motor block regression stratified by intrathecal dose, median time to ambulation and median time to S3 dermatome recovery of sensation to cold.

Results are presented in Table 1. The maximum time to straight leg raising in outliers was greater with increasing intrathecal dose used, although this study was not powered to examine differences between groups. For sensory block regression, there were significant outliers; four patients in the intrathecal group took 15–21 h for complete motor block regression and four patients in the epidural group took 16–27 h for complete sensory block regression. There were no cases of postpartum neuropathy.

Using 12.5 mg intrathecal 0.5% hyperbaric bupivacaine, Chapron et al. found the median (IQR [range]) time to complete motor block resolution was 3.7 (3.2–4.2 [1.5–5.0]) h [3]. However, the use of a different dose, concentration and motor block endpoint makes it difficult to directly compare our findings with previous studies. Additionally, there are likely other confounders such as the management of shivering using intravenous dexmedetomidine in some of our patients, that may possibly affect block regression [4]. Unlike intrathecal 0.5% hyperbaric bupivacaine, we found a general lack of block regression data involving 0.75% hyperbaric bupivacaine, and specifically using time to straight leg raising as an endpoint in the obstetric population.

As > 50% of patients continued to have significant motor block at 4 h following spinal anaesthesia, we extended the time trigger to 6 h. The proportion of patients in our cohort who met the review criteria decreased from 63% to 23% when this threshold was increased. Particularly during periods of high workload, we found excessive reviews with a 100% uneventful outcome have led providers to underestimate the importance of the review process. To raise the specificity for detection of complications, we have since updated our institutional protocol to incorporate an additional criterion: motor and sensory evaluations that have either not improved or worsened over two consecutive assessments. In our experience, this question was frequently asked during assessments to determine if further actions were required. We also found incorporating this criterion at time 0 has significantly decreased the number of reviews triggered while preserving timely review and escalation of care for those with an unusual regression course. Further study on obstetric neuraxial regression times with intrathecal 0.75% hyperbaric bupivacaine and the impact of various time triggers used for neurological monitoring protocols is required.

椎管内麻醉后长时间的运动阻滞退化应促使仔细评估严重的产后神经损伤和并发症，如脊柱血肿。建议在椎管内麻醉后 4 小时进行直腿反重力抬高的能力作为触发复查的时间阈值 [ 1 ]。然而，使用这个时间阈值，我们观察到大量患者需要进行审查，导致我们发现难以维持的劳动密集型过程[ 2 ]。触发因素过多的一个可能解释可能与我们机构使用的局麻药剂量增加有关，这种做法始于 COVID-19 大流行期间并一直持续至今。我们假设脊髓或硬膜外麻醉后运动阻滞回归的中位时间为 > 4 小时。为了测试这一点，我们进行了一项回顾性队列研究，以表征剖腹产椎管内麻醉后感觉和运动阻滞消退的持续时间（图 1）。

该研究被视为质量改进项目，不需要研究伦理委员会的批准。数据来自 200 名患者，接受鞘内注射（n = 100，0.75% 高压布比卡因加芬太尼 10-15 mcg 和吗啡 100 mcg）和硬膜外注射（n = 100，利多卡因 2% 加肾上腺素 1:200,000、芬太尼 50-100 mcg 和吗啡 1.5）从 2021 年 12 月至 2022 年 2 月期间的患者记录中回顾性收集了择期或紧急剖腹产的麻醉剂量 –2 mg）。根据我们的标准机构方案进行了感觉和运动评估。主要结果是运动阻滞回归的中位时间（定义为鞘内注射或硬膜外补充时间）到直腿抬高恢复的时间，使用 Kaplan-Meier 曲线和通过 Mantel-Haenszel 方法获得的风险比进行分析。次要结果是按鞘内剂量分层的运动阻滞回归的中位时间、行走的中位时间和 S3 皮节冷感觉恢复的中位时间。

结果如表 1 所示。随着鞘内剂量的增加，离群值中直腿抬高的最长时间也更长，尽管这项研究并未检验组间差异。对于感觉块回归，存在显着的异常值；鞘内组中的 4 名患者需要 15-21 小时才能完成运动阻滞消退，硬膜外组中的 4 名患者需要 16-27 小时才能完成感觉阻滞消退。无产后神经病变病例。

Chapron 等人使用 12.5 mg 0.5% 高压布比卡因鞘内注射。发现完成运动阻滞解决的中位时间（IQR [范围]）为 3.7 (3.2–4.2 [1.5–5.0]) 小时 [ 3 ]。然而，使用不同的剂量、浓度和运动阻滞终点使得我们很难将我们的发现与之前的研究直接进行比较。此外，可能还存在其他混杂因素，例如我们的一些患者使用静脉注射右美托咪定治疗颤抖，这可能会影响块回归[ 4 ]。与鞘内注射 0.5% 高压布比卡因不同，我们发现普遍缺乏涉及 0.75% 高压布比卡因的块回归数据，特别是使用直腿抬高时间作为产科人群的终点。

由于 > 50% 的患者在脊髓麻醉后 4 小时内继续出现明显的运动阻滞，因此我们将触发时间延长至 6 小时。当这个阈值增加时，我们队列中符合审查标准的患者比例从 63% 下降到 23%。特别是在工作量大的时期，我们发现过多的审核却导致 100% 平安无事的结果，导致提供商低估了审核流程的重要性。为了提高并发症检测的特异性，我们更新了我们的机构方案，纳入了一项附加标准：在连续两次评估中运动和感觉评估没有改善或恶化。根据我们的经验，在评估过程中经常会问这个问题，以确定是否需要采取进一步的行动。我们还发现，在时间 0 纳入此标准显着减少了触发的审查数量，同时保留了对那些具有异常回归过程的人的及时审查和升级护理。需要进一步研究鞘内注射 0.75% 高压布比卡因的产科椎管内消退时间以及用于神经监测方案的各种时间触发因素的影响。