Effect of the duration of electrical stimulation on the analgesic responsein patients with low back pain

Background: Electrical stimulation of peripheral nerves produces acute anal gesic effects. This randomized, sham-controlled, crossover study was design ed to evaluate the effect of differing durations of electrical stimulation on the analgesic response to percutaneous electrical nerve stimulation in 7 5 consenting patients with low back pain. Methods: All patients received electrical stimulation for four different ti me intervals (0, 15, 30, and 45 min) in a random sequence over the course o f an 11-week study period. All active percutaneous electrical nerve stimula tion treatments were administered using alternating frequencies of 15 and 3 0 Hz three times per week for 2 consecutive weeks, The prestudy assessments included the health status survey short form questionnaire and 10-cm visua l analog scale scores for pain, physical activity, and quality of sleep, wi th 0 being the best and 10 being the worst. The pain scoring was repeated 5 -10 min after each 60-min study session and 24 h after the last treatment s ession with each of the four methods. The daily oral analgesic requirements were assessed during each of the four treatment blocks. At the end of each 2-week treatment block, the questionnaire was repeated. Results: Electrical stimulation using percutaneously placed needles produce d short-term improvements in the visual ana-log scale pain, physical activi ty, and quality of sleep scores, and a reduction in the oral analgesic requ irements. The 30-min and 45-min durations of electrical stimulation produce d similar hypoalgesic effects (48 +/- 21% and 46 +/- 19%, respectively) and were significantly more effective than either 15 min (21 +/- 17%) or 0 min (10 +/- 11%). The 30- and 45-min treatments were also more effective in im proving physical activity and sleep scores over the course of the 2-week tr eatment period. In contrast to the sham treatment (0 min), the health statu s survey short form revealed that electrical stimulation for 15 to 45 min t hree times per week for 2 weeks improved patient function. Conclusion: The recommended duration of electrical stimulation with percuta neous electrical nerve stimulation therapy is 30 min.