Effective analgesia for extracorporeal shock wave lithotripsy: transcutaneous electrical nerve stimulation

Extracorporeal shock wave lithotripsy (ESWL) has revolutionized the treatment of urinary stone disease. However, the most appropriate analgesia offering pain-free treatment, minimal side effects, and adequate cost effectiveness remains to be established. This prospective study was performed to evaluate the efficacy of transcutaneous electrical nerve stimulation (TENS) during ESWL using third-generation lithotripters.

Two pairs of stimulator electrodes were placed paravertebrally at L1 and near the lithotripter shock tube before ESWL. Treatment was carried out as follows: (a) shock wave administration was begun (no current = sham TENS); (b) in the case of severe pain, TENS was begun; and (c) if patients experienced no pain relief, analgesic drugs were given intravenously.

Of 149 patients, 92 (62%) did not need any analgesia (neither TENS nor medication). In 42 (72%) of the remaining 57 patients, a TENS-related, pain-relieving response was observed. ESWL-induced pain could be reduced by 39.2%. The degree of fragmentation assessed by two urologists was found to be 90% for patients receiving TENS compared with a retrospectively analyzed control group (94%, n = 100).

Two different theories explaining TENS-related analgesia are known: segmental (spinal) and supraspinal (central) inhibition. Since we did not observe any analgesic effect in patients having both pairs of electrodes attached around the shock tube (n = 30), supraspinal inhibition obviously accounts for the abovementioned pain relief. We conclude that TENS is a noninvasive, cost-effective method to achieve side-effect-free analgesia in ESWL using third-generation lithotripters.