Effect of 2% Topical Lidocaine Gel on Discomfort from Electrical Stimulation During Nerve Conduction Studies- A Prospective Double-Blind Placebo-Controlled Study

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Abstract
Purpose: Procedure discomfort can limit electrodiagnostic studies. Reducing discomfort can maximize the benefits of these diagnostic tools. This study targeted the discomfort associated with nerve conduction studies (NCS). Patients and Methods: This was a prospective randomized double-blind placebo-controlled study comparing the effect of topical lidocaine gel (2%) versus analgesic-free lubricant gel (K-Y gel) on pain perception during NCS. Sequential patients (n=130) referred for routine NCS participated in the study. We applied 1 mL of lidocaine gel to one palm, and 1 mL of K-Y gel to the other as a control. After 20– 45 min of application, graded increments of electrical stimulation intensity were delivered to record the median and ulnar mixed palmar nerve responses. Patients were then asked to score the degree of pain felt from electrical stimulation over each palm using the Wong-Baker Faces Pain Scale (WBFPS) and the Numeric Rating Scale (NRS), independent of baseline pain. Results: Mean WBFPS and NRS scores for lidocaine-treated palms were significantly lower than those for controls using parametric paired t-test (3.79 vs 4.37 and 3.35 vs 3.78 respectively, all p-values< 0.05). Subgroup analysis showed a significant decrease in mean scores in females, patients aged ≤ 50 years, patients without a history of previous NCS, and patients without comorbidities (all p-values< 0.05). Median scores using nonparametric Wilcoxon ranked test also showed statistically significant differences (all p-values< 0.05). Conclusion: The results indicate that topical lidocaine 2% gel reduces discomfort associated with NCS. However, despite the statistical significance, clear clinical significance may be lacking. Clinical implementation may be considered for the subgroups that showed the greatest benefit. Further studies that incorporate more efficient drug delivery methods may yield better results.

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