Objective: To compare the efficacy of different local anaesthetics to produce intradermal anaesthesia for venous cannulation and the discomfort associated with skin infiltration.
Design: Randomized, double blind study.
Setting: Induction room of a university hospital.
Patients: Convenience sample of 600 patients (18-65 years; ASA I-II) scheduled for elective surgery.
Interventions: Patients received one of six preparations: 0.9% saline, 1% prilocaine (Xylonest), 1% lidocaine (Xylocain), 1% mepivacaine-1 (Meaverin), 1% mepivacaine-2 (Scandicain), 1% procaine (Novocain). A skin wheal was raised on the dorsum of the hand by injecting 0.1 ml intradermally and 0.1 ml subcutaneously via a 27-g hypodermic needle. 60 seconds later an 18-g intravenous cannula was passed through that skin wheal into a vein.
Measurements: A visual analog scale (VAS) for pain (0 = no pain/10 = most pain imaginable) was used to assess pain elicited by raising the skin wheal and inserting the cannula.
Main results: With regard to analgesic potency all five local anaesthetics were comparable (mean VAS-score 1.7-2.09) and effective when compared to 0.9% saline (mean VAS-score 4.2; P < 0.001). Infiltration pain was least with mepivacaine-1 (mean VAS-score 1.0; P < 0.001) and highest with procaine (mean VAS score 2.7; P < 0.001).
Conclusions: Of the local anaesthetics tested, Mepivacaine-1 is the drug of choice for skin infiltration as its injection elicits least discomfort.