Topical amethocaine (Ametop(TM)) is superior to EMLA for intravenous cannulation

Purpose: A eutectic mixture of local anesthetics (EMLA) is commonly used to provide topical anesthesia for intravenous (iv) cannulation. One of its side effects is vasoconstriction, which may render cannulation more difficult. A gel formulation of amethocaine (Ametop(TM)) is now commercially available. The aim of this study was to compare EMLA and Ametop(TM) with regard to the degree of topical anesthesia afforded, the incidence of vasoconstriction and the ease of iv cannulation. Methods: Thirty two ASA I adult volunteers had a 16 gauge iv cannula inserted on two separate occasions using EMLA and Ametop(TM) applied, in a double blind fashion for topical anesthesia. Parameters that were recorded after each cannulation included visual analogue pain scores (VAPS), the presence of vasoconstriction and the ease of cannulation, graded as: 1 = easy, 2 = moderately difficult, 3 = difficult and 4 = failed. Results: The mean VAPS ± SD after cannulation with Ametop(TM) M was 12 ± 9.9 and with EMLA was 25.3 ± 16.6 (P = 0.002). Vasoconstriction occurred after EMLA application on 17 occasions and twice after Ametop(TM) (P = 0.001). The grade of difficulty of cannulation was 1.44 ± 0.88 following EMLA and 1.06 ± 0.25 with Ametop(TM) (P = 0.023). Conclusions: Intravenous cannulation was less painful following application of Ametop(TM) than EMLA. In addition, Ametop(TM) caused less vasoconstriction and facilitated easier cannulation. Its use as a topical anesthetic agent is recommended, especially when iv access may be problematic.