Background and objective: Eutectic mixture of local anaesthetic cream and lidocaine iontophoresis are effective in providing analgesia for peripheral venous cannulation with small gauge cannulae in adults and children. The objective of this study was to compare the analgesic efficacy of the two techniques directly in patients using larger cannulae.
Methods: In a double-blind, randomized, controlled study we compared the two techniques directly. Twenty-eight patients had the eutectic mixture of local anaesthetic cream applied to the dorsum of one hand for 60 min followed by sham iontophoresis (group EMLA); the other hand had a sham cream applied for 60 min followed by 10 min of 2 mA iontophoresis with lidocaine 4% and epinephrine 1 in 50,000 (group iontophoresis). Within 5 min of completion of iontophoresis an anaesthetist, unaware of treatment allocation, inserted 18-G venous cannulae into veins of both hands. The patient then scored the amount of pain on cannulation using a 10 point verbal rating scale.
Results: Eight patients were excluded from analysis due to failed cannulation (two group EMLA, two group iontophoresis), intolerable burning sensation from iontophoresis (one), protocol violation (one), and changes in surgical schedule (two). Pain scores were lower for the EMLA treated hand than for the iontophoresis side (median (range) 1 (0-7) vs. 3 (0-6); P = 0.023). Erythema and paraesthesia were common but short lived on the iontophoresis side.
Conclusions: Although lidocaine iontophoresis is effective more quickly than the eutectic mixture of local anaesthetic cream, the superior quality of analgesia produced by the eutectic mixture in this study should be borne in mind if these treatments are used electively.