Contribution of a heating element to topical anesthesia patch efficacy prior to vascular access: results from two randomized, double-blind studies.
BACKGROUND
Pain associated with superficial procedures, including intravenous (IV) access procedures, should be prevented when possible, especially in children.


OBJECTIVE
To evaluate a topical local anesthetic patch containing lidocaine 70 mg/tetracaine 70 mg with a heating element designed to warm the skin and facilitate rapid delivery of local anesthetics into the skin. The pilot study was designed to provide data to inform the design of the definitive study to evaluate the impact of controlled heat on the efficacy of the lidocaine/tetracaine patch (patch) when applied before IV cannulation.


METHODS
Subjects in the pilot study were randomized to eight groups that varied by heated vs. unheated patch, 20 vs. 30 minute application, and 16 vs. 18 G catheter. Subjects in the definitive study were randomized in a double-blind manner to receive either the heated or unheated patch, 20 minutes before vascular access, using a 16 G catheter in the antecubital space of the arm. In both studies, the primary efficacy measure was subject-reported pain intensity using a visual analog scale.


RESULTS
Pilot study: Subjects who received the heated patch (n=43) vs. the unheated patch (n=37) had lower mean pain intensity scores (14.7 vs. 23.5mm, P=0.04). Pain intensity scores did not differ significantly by application time, but the difference between the 16 and 18 G catheter groups approached statistical significance (22.8 vs. 14.9 mm, P=0.05). Definitive study: Mean pain intensity scores for the heated patch group (n=124) vs. the unheated patch group (n=126) were 14.2 and 20.5mm, respectively (P=0.006).


CONCLUSIONS
Heated patches provided significantly better pain relief compared with unheated patches. All the subjects tolerated the patches well, with few adverse effects.
Masud
Salman
S
Shriners Hospitals for Children, University of Utah, Salt Lake City, Utah 84103-4399, USA. smasud@shrinenet.org
Wasnich
Richard D
RD
Ruckle
Jon L
JL
Garland
William T
WT
Halpern
Stephen W
SW
Mee-Lee
Denis
D
Ashburn
Michael A
MA
Campbell
John C
JC
D000279:Administration, Cutaneous; D000293:Adolescent; D000328:Adult; D000368:Aged; D000698:Analgesia / Q000379:methods*; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000627:therapeutic use; D004311:Double-Blind Method; D005260:Female; D006358:Hot Temperature / Q000627:therapeutic use*; D006801:Humans; D008012:Lidocaine / Q000008:administration & dosage / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000209:etiology / Q000517:prevention & control*; D010147:Pain Measurement; D018962:Phlebotomy / Q000009:adverse effects*; D010865:Pilot Projects; D016896:Treatment Outcome
D000779:Anesthetics, Local; D008012:Lidocaine