• T Tritrakarn, J Lertakyamanee, P Koompong, S Soontrapa, P Somprakit, A Tantiwong, and S Jittapapai.
• Department of Anesthesiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand. sitti@mahidol.ac.th
• Anesthesiology. 2000 Apr 1;92(4):1049-54.

BackgroundThe objectives were to determine whether a eutectic mixture of local anesthetic (EMLA) or placebo cream reduces pain during extracorporeal piezoelectric shock wave lithotripsy (EPSWL), and to determine which of the components of the application (i.e., the occlusive dressing, the cream, or the local anesthetic) contributes to analgesia.MethodsA randomized, double blind, crossover study (part 1) was performed in 12 patients who were scheduled for EPSWL procedures on an ambulatory basis who received the first treatment without any intervention and who had verbal pain scores of 70 or more (on a 0-to- 100 scale). For the next two treatments at 2-week intervals, patients were randomly assigned to receive either 10 g EMLA or 10 g placebo cream and then crossed over to receive the other. The cream and occlusive dressing were left in place and immersed in water throughout the procedure. Verbal numeric pain score was assessed at 5 min after receiving the maximal tolerable intensity of shock wave and at the end of the procedure. The study continued (part 2) in 202 ambulatory patients; 125 men and 77 women, American Society of Anesthesiologists physical status I and II, subjected to EPSWL were randomly allocated into five groups who received (1) nothing on the skin (control), (2) plastic occlusive dressing, (3) placebo cream and plastic occlusive dressing, (4) EMLA cream and plastic occlusive dressing, (5) EMLA cream and plastic occlusive dressing for 60 min to achieve cutaneous anesthesia, which was removed before EPSWL. Pain score was evaluated 10 min into the procedure and at the end of the procedure.ResultBoth parts of the study showed that patients who received either EMLA or placebo cream with dressing throughout the procedure experienced less pain and tolerated higher energy levels compared with the control. Patients who received only pre-EPSWL cutaneous anesthesia of EMLA and who received only the occlusive dressing did not have a reduction in pain score.ConclusionsEMLA and placebo creams under occlusive dressing reduced pain during EPSWL. The presence of the cream itself as a coupling medium contributed to analgesia. This may be a useful, simple, safe, and economical adjuvant technique to reduce pain during immersion EPSWL.

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