Wang Z. et al., 2020: Eutectic mixture of local anaesthetics for pain reduction during extracorporeal shockwave lithotripsy: A systematic review and meta-analysis
Wang Z, Chen G, Wang J, Wei W.
Department of Urology, Institute of Urology, West China Hospital, Sichuan University, Chengdu, China.
A systematic review and meta-analysis was conducted to explore the effect of a eutectic mixture of local anaesthetics (EMLA) on pain reduction during extracorporeal shockwave lithotripsy (ESWL). PubMed, Web of Science, Embase, EBSCO, and Cochrane library databases (updated March 2020) were searched for randomised controlled trials (RCTs) assessing the effect of EMLA for patients that underwent ESWL. The search strategy and study selection process were managed according to the PRISMA statement. Six RCTs were included in the meta-analysis. Overall, the results indicated that EMLA significantly reduced pain compared to the control group (RR = -2.98, 95% CI = -5.82 to -0.13, P = 0.04) with a heterogeneity of I2 = 57% (P = 0.04). Subgroup analysis showed that EMLA did not significantly reduce pain when the patients took an analgesic premedication (RR = -1.46, 95% CI = -5.89 to 2.98, P = 0.52) with a heterogeneity of I2 = 38% (P = 0.52). Conversely, studies without premedication showed a significant pain relief effect (RR = -4.08, 95% CI = -7.36 to -0.65, P = -0.80) with a heterogeneity of I2 = 48% (P = 0.14). Most studies showed there was no difference in the patient's need for analgesics. EMLA was effective for reducing pain during EWSL. However, this analgesic effect was limited and did not reduce the need for analgesics.
PLoS One. 2020 Oct 5;15(10):e0237783. doi: 10.1371/journal.pone.0237783. eCollection 2020. PMID: 33017397
One of the great advantages with SWL is that stone removal can be accomplished without regional or general anaesthesia. Contrary to what urologist in general believe, this was also the case for the original unmodified Dornier HM3 lithotripter.
I personally used that device for stone disintegration between 1987 and 1998 without regional or general anaesthesia.
The purpose of modifying the geometrical properties of the shockwave in late generations of lithotripters was to enlarge the entrance area of the shockwave at the skin level. That modification reduced skin pain. Accordingly, most modern lithotripters have a large entrance angle (and consequently a relatively small focal volume). This observation led to attempts with methods for skin surface anaesthesia.
By applying EMLA-cream on the skin at the entrance of the shockwave, the purpose was to further decrease the pain experience at that level and make the treatment more comfortable for the patient. That was also the purpose of our initial study . Was application of EMLA-cream clinically useful or not?
The current article is a systematic review of the literature to draw conclusions on the value of EMLA. The conclusion was that EMLA only had limited analgesic effect and that administration of other analgesics cannot be omitted when EMLA was applied.
My own interpretation of the experience more than 30 years ago was that although reduced pain could be achieved when EMLA had been applied this was the case only when shockwaves were administered at low-energy levels. At higher energy levels visceral pain dominated and the presence of EMLA was clinically un-important.
Apart from the pain, one other factor that needs to be considered is the patient’s anxiety. It is possible that application of EMLA-cream before SWL has a psychological effect and thus makes the patient more tolerant to pain.
The basic pre-requisite for success with SWL is, however, to give the patient adequate pain relief. If such measures fail; the treatment will fail as well. In my own experience this goal is attained by administration of small intermittent doses of alfentanil and propofol.
1.Tiselius HG. Cutaneous anaesthesia with lidocaine-prilocaine cream: a useful adjunct during shock wave lithotripsy with analgesic sedation. J Urol 1993;149:8-11