Elevated electrical stimulation thresholds for sciatic nerve block in individuals with diabetic complications: a systematic review and meta-analysis

Diabetes mellitus is associated with peripheral nerve structural alterations, potentially affecting nerve excitability. Electrical stimulation threshold is a key parameter for nerve localization during sciatic nerve block. This meta-analysis investigates the impact of diabetes mellitus and its complications on this threshold. We systematically searched multiple databases, including PubMed, Embase, Web of Science, Cochrane Library, Scopus, China National Knowledge Infrastructure (CNKI), and Wanfang Database, from their inception to November 10, 2025, for studies comparing electrical stimulation thresholds during sciatic nerve block between diabetic and non-diabetic subjects. The methodological quality of included studies was assessed using the Newcastle‑Ottawa Scale (NOS). Data were pooled using random-effects models. Sensitivity analyses were conducted by alternating effect models and sequentially excluding individual studies. Subgroup analyses were performed to explore potential sources of heterogeneity. In addition, trial sequential analysis (TSA) was applied to determine whether the sample size was sufficient and to assess statistical power. The quality of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) framework. Six studies involving 486 participants were included, all of which were of high quality according to the NOS. The pooled analysis demonstrated a significantly higher stimulation threshold in diabetic participants compared to controls (mean difference [MD] = 0.57 mA, 95% confidence interval [CI]: 0.22–0.91, P = 0.001), with substantial heterogeneity ( I 2 = 94%). Sensitivity analyses, including alternating effect models and sequential exclusion of individual studies, confirmed the robustness of these findings. Subgroup analysis identified the presence of diabetic complications (peripheral neuropathy or diabetic foot) as a significant source of heterogeneity ( P = 0.02), while geographic region and puncture site were not associated with heterogeneity ( P > 0.05). TSA indicated that the evidence was robust, with sufficient statistical power to support the conclusion. The result was supported by low evidence. Diabetic complications, particularly peripheral neuropathy or diabetic foot, are associated with elevated electrical stimulation thresholds for sciatic nerve block. This suggests that procedural parameters may need adjustment in this patient subgroup to ensure accurate nerve localization.