Effect of transcutaneous electrical acupoint stimulation on post-anesthetic shivering: a meta-analysis and trial sequential analysis

To The Editor, We have read with great sincerity the article “Effect of transcutaneous electrical acupoint stimulation on post-anesthetic shivering: a meta-analysis and trial sequential analysis” by Miao et al[1]. The study demonstrates a commendable effort to systematically synthesize evidence from multiple randomized controlled trials, providing valuable insights into the efficacy and safety of transcutaneous electrical acupoint stimulation (TEAS) for post-anesthetic shivering. The authors should be praised for their meticulous literature search, rigorous trial selection, and the use of trial sequential analysis, which enhances the reliability of their findings. However, we believe certain methodological aspects warrant further clarification or adjustment to strengthen their validity. First, intraoperative and perioperative temperature management strategies, such as forced air warming, prewarming, operating room temperature, and continuous core temperature monitoring, were not systematically taken into account in the meta-analysis. One of the main causes of postoperative shivering is perioperative hypothermia, and one significant constraint and potential confounding factor affecting the observed incidence and severity of shivering is the lack of reporting and standardization of temperature control techniques. The need to consider intraoperative and perioperative temperature control protocols in shivering studies is highlighted by recent evidence showing that active warming interventions significantly raise core body temperature and lower the risk of postoperative shivering through improved temperature management[1]. Second, the Baseline Shivering Assessment Scale (BSAS) was employed to measure shivering, but the analysis did not stratify results according to severity; instead, it concentrated only on the overall incidence of shivering. This restricts our ability to determine if TEAS is useful in lowering episodes of severe or clinically significant shivering, which are more pertinent to patient outcomes. The significance of including shivering severity in outcome assessments is highlighted by the fact that recent meta-analyses assessing preventive interventions for postoperative shivering, such as intravenous acetaminophen, have included severity-based analyses and shown significant reductions in both overall and severe shivering[2]. Third, there was an absence of a specific assessment of TEAS dose-response relationship. These differences were pooled without systematic subgroup analysis or meta-regression to investigate parameter-dependent effects, despite the fact that the randomized controlled trials that were part of the analysis used heterogeneous stimulation parameters, such as variations in frequency, acupoint selection, and treatment duration. While ideal stimulation settings have not yet been determined, evidence from parameter-focused systematic reviews suggests that the therapeutic effects of TEAS and electroacupuncture may differ depending on stimulation dose and technological features[3]. Therefore, protocol standardization, reproducibility, and the clinical interpretability of the results are limited by the lack of dose-response assessment in the current meta-analysis, especially for a device-based intervention where treatment intensity and configuration are likely to affect therapeutic efficacy. Miao et al’s meta-analysis provides valuable evidence supporting the efficacy and safety of TEAS for post-anesthetic shivering and is commendable for its rigorous methodology. However, limitations such as the lack of perioperative temperature control data, absence of severity-stratified outcomes, and lack of dose-response assessment restrict the clinical applicability of the findings. Future studies addressing these issues are needed to strengthen the validity and interpretability of TEAS interventions. This letter to the editor adheres to the Transparency in the Reporting of Artificial Intelligence in Research (TITAN) guideline[4].