Radial artery cannulation: topical amethocaine gel versus lidocaine infiltration.

Background: In a prospective randomized study, we compared topical 4% amethocaine gel (Ametop) with 2% lidocaine infiltration for analgesia for radial artery cannulation. A previous study had shown topical analgesia with EMLA cream reduced pain, shortened cannulation time, and improved success rates when compared with lidocaine infiltration.

Methods: One hundred adult patients undergoing elective cardiac surgery were randomized. Cannulation times and success rates were compared between the two groups. The quality of analgesia was assessed using a visual analogue scale (VAS) and four-point verbal pain scoring system.

Results: Ninety-nine sets of data were analysed using Mann-Whitney U and chi-squared tests. Mean time to cannulation was 56 s in the amethocaine group (interquartile range (IQR) 41-142) and 59 s in the lidocaine group (IQR 40-105). The median pain score on the VAS was 2 in both groups (IQR 1-3.5 for amethocaine and 0-4 for lidocaine).

Conclusions: There was no significant difference between these two methods of analgesia for any measured variable.