I'll be attending a talk in the next couple weeks about research done into pain control for IV sticks, using low-frequency ultrasound as part of the protocol. The hypothesis is that the LFUS speeds the absorption of topical Lidocaine gel into the skin, so that it is faster-acting. Here's the abstract and citation, then I have some questions:

Ultrasound with Topical Anesthetic Rapidly Decreases the Pain of Intravenous Sticks in the Emergency Department

ABSTRACT

OBJECTIVE: Use of topical analgesia in the ED for needlesticks has been limited by time constraints. Brief ultrasound treatment of skin increases permeation rates of hydrophobic topical medications. This study sought to show that ultrasound treatment followed by brief application of topical anesthetic decreased the pain of intravenous (IV) sticks in the ED.

METHODS: Design: Randomized, controlled, prospective trial carried out in a university hospital ED. Participants: 89 consecutive English-speaking, subcritically injured or ill adult patients able to give consent, receiving an IV as part of their standard care from July to October 2003. Intervention: Participants received either a brief ultrasound treatment using the Sonoprep device followed by 5 minutes of LMX 4% lidocaine cream and standard care (an alcohol skin prep) or standard care alone followed by an IV start. Participants rated the pain on a visual analog scale (VAS) 1-10. Researchers assessed the site after IV insertion and 24 hours later. Primary outcome was the participant's subjective pain score. Secondary outcome was site skin irritation. Data were entered and analyzed using SAS with Wilcoxon rank sum, chi-square, and Fisher's exact tests.

RESULTS: There were no significant differences in demographics, or site skin irritation either immediately (p = 0.249) or at 24 hours (p = 0.187). The treatment group reported significantly less pain with the IV (p < .0001), with 80% of treated participants reporting pain scores 3 versus only 37% of controls (p < .0001).

CONCLUSIONS: The Sonoprep ultrasound device applied to skin for 15 seconds followed by 5 minutes of LMX 4% lidocaine cream significantly reduced the pain of IV starts in subcritically injured or ill adult ED patients. The treatment was safe, effective, and did not interfere with the course of these patients' care in a busy ED.

Academic Emergency Medicine Volume 11, Number 5 494-495,
© 2004 Society for Academic Emergency Medicine

http://www.aemj.org/cgi/content/abstract/11/5/494-b?ct

...Okay, so I am a long way from being a sophisticated evaluator of research, but question number one for me is this: doesn't this methodology basically compare and contrast US plus topical gel versus no pain control at all? And isn't there an important underlying assumption, i.e. that if the topical gel is doing anything within 5 minutes, that action must be attributable to the US? And to really show that, shouldn't there be a group someplace in the study who got topical Lido for five minutes, but no US?

I would hate to miss out on cool, good research because my limited experience makes me jaded and overly skeptical. I will have the chance to ask thoughtful, respectful questions of one of the investigators. Any suggestions for what those might be?

(Plus, I realize that even trying to quantify pain in the first place is your basic data nightmare.)

From the sound of it, a really poor study. Even placebo cream and faux US treatments would have resulted in "significantly less pain". My opinion is that this is a worthless study probably paid for by the manufacturer of this "Sonoprep" device. There are too many similarly lousy studies in the EM literature.

Sess' is right. To really do this study right you need 4 arms. real ultrasound with real anesthetic gel, real ultrasound with fake anesthetic gel, fake ultrasound with real gel, and fake ultrasound with fake gel. That way you can make some estimate of the effect of ultrasound and/or anesthetic gel on pain. Otherwise you might as well just dance around the patient counter clockwise while chanting in gaelic and then ask the patient if that made their pain less.

Unfortunately the EM literature has way too much of this kind of stuff.

This press release implies they did have a more appropriate placebo arm

http://www.prnewswire.com/cgi-bin/stories.pl?ACCT=104&STORY=/www/story/12-14-2004/0002631189&EDATE=

However, I'm not sure I believe their statement that existing lidocaine products require 30-60 minutes. I've use LET and EMLA plenty of time with less than 15 minutes of treatment with fine results.

This press release implies they did have a more appropriate placebo arm

http://www.prnewswire.com/cgi-bin/stories.pl?ACCT=104&STORY=/www/story/12-14-2004/0002631189&EDATE=

However, I'm not sure I believe their statement that existing lidocaine products require 30-60 minutes. I've use LET and EMLA plenty of time with less than 15 minutes of treatment with fine results. Yes, I found another abstract, for a followup Peds-only study they did, and there was placebo gel involved there. Plus my classmate the researcher tells me there was some placebo control not referenced on the poster, or in the abstract (which mystifies me).

So it's good to have my suspicions confirmed -- I agree about the four arms of the study, and I really question their rock-solid assumption that the real stuff works in 30 minutes or doesn't work at all. Thanks! I guess at the talk, I get to be the skeptical guy. That's always fun. :meanie: