Transcutaneous electrical nerve stimulation for relieving acute pain in the prehospital setting: a systematic review and meta-analysis of randomized-controlled trials.

Although medics in many services are equipped with pharmacological analgesia, legislative or logistical restrictions in some systems result in the need to rely on nonpharmacological avenues for the management of acute pain. Transcutaneous electrical nerve stimulation (TENS) has been proposed as an alternative to analgesic medication that could be feasible and effective in the prehospital setting. The aim of this systematic review was to determine the effectiveness and safety of TENS when administered by medics to patients with acute pain in the prehospital setting. A systematic literature review was carried out to identify randomized-controlled trials investigating the safety and efficacy of TENS compared with 'sham' (placebo) TENS in the prehospital setting. Quality assessment of included studies was carried out to identify potential for bias. Qualitative and quantitative synthesis of results was performed to determine effectiveness and safety. The studies included were meta-analysed using a random-effects model to produce pooled results for comparison of the mean post-treatment pain scores using a visual analogue scale (VAS). Four studies were included in the analysis, all of which were prospective clinical trials of good methodological quality. Meta-analysis indicated that TENS produced a clinically significant reduction in severity of pain [mean VAS reduction 38 mm (95% confidence interval 28-44); P<0.0001] for patients with moderate-to-severe acute pain. TENS produced post-treatment mean pain scores that were significantly lower than 'sham' TENS [33 mm VAS (95% confidence interval 21-44); P<0.0001]. TENS was also effective in reducing acute anxiety secondary to pain. No safety risks were identified. When administered by medics in the prehospital setting to patients with acute pain, TENS appears to be an effective and safe nonpharmacological analgesic modality that should be considered by emergency medical services organizations in which pharmacological pain management is restricted or unavailable.