Letter to the editor regarding: ‘Effects of daytime variation on pain intensity and analgesic requirement after cesarean section: a retrospective and prospective study’

To the editor

We read the article by Shu et al. [1] with great interest. This study, through a combination of retrospective and prospective cohort designs, investigated the impact of cesarean section timing on postoperative pain and analgesic requirements. It revealed that patients undergoing surgery in the afternoon experienced higher pain intensity within 24 h postoperatively, greater analgesic consumption, reduced pain tolerance, and more pronounced stress responses. These findings offer a novel perspective for developing individualized analgesic strategies following cesarean delivery. However, we believe several key issues still warrant further consideration.

Firstly, the monitoring of endocrine and inflammatory rhythmic indicators should be expanded. While the study measured IL-6 and endorphins, it did not include other relevant circadian factors such as cortisol and melatonin. Cortisol exhibits diurnal variation and may modulate pain through its influence on inflammation, whereas melatonin has analgesic properties and peaks at night. Its lower levels in the afternoon could potentially contribute to increased postoperative pain [2,3]. Therefore, future studies should assess the dynamic changes in these biomarkers before and after surgery to elucidate the molecular mechanisms underlying time-dependent pain variations.

Secondly, the individualization and temporal adaptability of analgesic protocols require further exploration. The study solely employed intravenous patient-controlled analgesia, without evaluating whether alternative techniques-such as epidural analgesia or transversus abdominis plane block-could mitigate time-related pain differences. Comparative analyses of various analgesic modalities across morning and afternoon surgeries are recommended to guide clinical decision-making [4]. Moreover, it is well established that opioid metabolism exhibits circadian variation due to fluctuations in CYP450 enzyme activity. The study did not investigate whether faster drug clearance in afternoon surgeries led to inadequate analgesia. Measuring the plasma concentration-time profile of sufentanil could help determine whether dosage adjustments based on surgical timing are necessary [3].

Thirdly, long-term follow-up should be extended and the risk threshold for surgical timing refined. At one-month post-surgery, the afternoon group showed slightly higher pain scores, approaching statistical significance; however, each group included only approximately 50 participants. Extending follow-up to 3–6 months and increasing the sample size would allow for a more robust assessment of whether acute pain differences evolve into chronic pain, thereby identifying potential targets for early intervention. Additionally, although the study suggests considering time factors in analgesic planning, it does not define a specific risk threshold for ‘afternoon surgery.’ Subgroup analysis is recommended to identify the peak period of highest pain risk, which could inform optimal scheduling practices.

In conclusion, we appreciate the valuable insights provided by Shu et al. regarding the influence of surgical timing on post-cesarean pain management. We look forward to further research that delves into the underlying mechanisms and provides more precise and actionable evidence for tailoring analgesic strategies and optimizing surgical scheduling for cesarean section patients.

Disclosure statement

The authors have no conflicts to report.

Data availability

Data availability is not applicable to this article as no new data were created or analyzed in this study.