Two-minute skin anesthesia through ultrasound pretreatment and iontophoretic delivery of a topical anesthetic: a feasibility study.

ABSTRACT

BACKGROUND AND OBJECTIVES: The pain associated with percutaneous procedures is a significant source of distress in clinical practice, especially in children. Topical anesthetics require 30-60 minutes to provide skin anesthesia; with iontophoresis, they minimally require 10 minutes, and with ultrasound pretreatment, 5 minutes. In this study, we assessed the feasibility of providing skin anesthesia to needle prick with the combination of ultrasound pretreatment and 2-minute low-voltage (1 mA) iontophoresis. We compared it with sham-ultrasound pretreatment and with standard, 10-minute high-voltage (4 mA) iontophoresis. METHODS: This is a single-blind, randomized, controlled, crossover study in healthy volunteers, specifically for the purpose of the study subjected to standardized needle prick. They rated the absolute pain associated with the needle prick on a 10-cm visual analog scale, with 0 being "no pain" and 10 being "extremely painful." RESULTS: Of the 31 subjects who consented to the study, 30 were randomized and completed the study. The mean duration of the ultrasound pretreatment was 21.4 seconds (range 6-85). The absolute pain scores for the ultrasound plus 2-minute low-voltage iontophoresis and the standard, 10-minute high-voltage iontophoresis were not statistically significantly different (0.9 +/- 0.31 vs 0.46 +/- 0.20; P = 0.49). However, they were statistically significantly different from the sham-ultrasound plus 2-minute low-voltage iontophoresis pain score (2.6 +/- 0.55) (P = 0.0001 and 0.0012, respectively). CONCLUSIONS: Ultrasound pretreatment plus 2-minute low-voltage iontophoresis provides better skin anesthesia than sham-ultrasound plus 2-minute low-voltage iontophoresis, and similar to standard, 10-minute high-voltage iontophoresis.