Run-of-the-mill lacerations come in half-a-dozen times a shift, and we have all been taught that irrigation is important. This just feels right on an intuitive level, too. Ever since Ignaz Semmelweis realized it was a good idea to wash one's hands when transitioning from the cadaver lab to performing pelvic exams on pregnant women (Rev Infect Dis 1981;3:808), the idea that cleaner is better has been central in transitioning medicine from the realm of barber surgeons into something like an actual science.
What should we be using for washout? Unless you trained in a particularly progressive program, the answer has historically been sterile normal saline, maybe with a dash of Betadine swirled in if you adopted the style of your orthopedic colleagues. Sterile definitely sounds like a desired quality in anything you're using to clean a wound, and normal saline is so ubiquitous in the ED that it might as well be tap water for all intents and purposes. Tap water is also ubiquitous in hospitals, not to mention available in copious quantities without accessing the Omnicell. Did I mention it's also free? It seems unlikely that a resource as pedestrian as tap water would be as safe as a sterilized electrolyte solution, but wouldn't it be great if it were?
Thankfully, this thought has occurred to several of our EM forebearers who were inquisitive and enterprising enough to look into this question using science! Way back in 1998, the good Dr. Moscati decided to test his theory on rats, presumably because they were readily available and complained less than medical students.
Wound Irrigation with Tap Water
Moscati RM, Reardon RF, et al.
Acad Emerg Med
The researchers made lacerations, inoculated them with Staphylococcus aureus, and compared bacterial counts pre- and post-irrigation with sterile saline or tap water. Saline reduced the bacterial load by about 50 percent, but tap water knocked the count down by more than 80 percent (p<0.05). This led them to conclude that tap water might be a viable and — for ease of use in many cases — preferable option for wound irrigation. Already using tap water on your rat lac repairs? What about humans? Thankfully, a 2003 study touches on this topic.
Wound Irrigation in Children: Saline Solution or Tap Water?
Valente JH, Forti RJ, et al.
Ann Emerg Med
This study randomized more than 500 consecutive patients 1-17 years old presenting with simple lacerations to receive irrigation with saline (minimum 100 mls) via syringe and 18-gauge angiocatheter or tap water (minimum of 10 seconds) directly under the faucet or using a two-foot disposable tube (for lacerations located in areas not easily placed in the sink). Wound infection rates were essentially identical, occurring in 2.8 percent and 2.9 percent of patients in the sterile saline and tap water groups, respectively.
Not to be outdone, Dr. Moscati came roaring back into the high-stakes world of tap water washouts in 2007 with a study of 715 adults (patients 17 and older) with simple lacerations who were also randomized (via envelope this time) to irrigation with sterile saline (200 ml minimum volume, presumably because adults are bigger than children) or tap water (minimum two minutes, this time with a three-foot disposable, nonsterile tube for lacerations that couldn't fit into the sink). They were able to obtain follow-up data on 634 patients, and again found no significant difference in the subsequent rate of infection (4% for tap water and 3% for sterile saline with a 95% CI of 0.5-2.7).
A Multicenter Comparison of Tap Water versus Sterile Saline for Wound Irrigation
Moscati RM, Mayrose J, et al.
Acad Emerg Med
An astute observer might note a difference in the technique and quantity of tap water used when compared with the sterile saline. One comes out of a tap in unlimited quantities; one comes in a bottle you have to request. Perhaps it's these differences that are skewing the results and giving tap water an unfair advantage? Dr. Weiss and his co-investigators agreed that these were worthy considerations.
Water is a Safe and Effective Alternative to Sterile Normal Saline for Wound Irrigation Prior to Suturing: A Prospective, Double-Blind, Randomised, Controlled Clinical Trial
Weiss EA, Oldham G, et al.
In what they note was the largest and “only study that was double-blinded and controlled for irrigation technique, pressures and solution volumes,” the authors analyzed data on 625 subjects 1 year and up with lacerations who were enrolled over an 18-month period. They used an 18-gauge angiocatheter to deliver 500 ml of sterile saline or tap water for wound irrigation. The providers who cleaned the wound and the providers who checked the wound were blind to solution type. They found no difference in the rate of infection between the two groups (3.5% for tap water, 6.4% for sterile saline with a 95% CI of -0.4-5.7%).
You've probably come to the conclusion that tap water is a reasonable alternative for wound irrigation. On the off chance that you're still doubting yourself and craving the sweet, sweet validation that can only be bestowed by a member of the Cochrane Collaboration, then here is a study for what ails you.
Water for Wound Cleansing
Fernandez R, Griffiths R
Cochrane Database Syst Rev
2012 Feb 15;2:CD003861
The authors of this analysis of nearly 1900 children and adults from five studies found no difference in the rate of infection when tap water or sterile saline was used for wound irrigation (OR 0.66 95% CI 0.42-1.04 for adults and OR 1.07 95% CI 0.43-2.64 for children). They concluded, “There is no evidence that using tap water to cleanse acute wounds in adults or children increases or reduces infection. There is not strong evidence that cleansing wounds per se increases healing or reduces infection. In the absence of potable tap water, boiled and cooled water as well as distilled water can be used as wound cleansing agents.”
You may have noticed that the Cochrane authors throw a line in their conclusion that the evidence for cleansing wounds at all is pretty weak. That may well be true, but in the absence of compelling evidence to the contrary, I think it's safe to assume that most providers are going to continue washing out wounds with something.
Hopefully, you'll decide in most cases that that something should be plain old tap water. I would be remiss, however, if I didn't mention all the studies here had a lot of crucial exclusion criteria, including any immunocompromising illness (diabetes qualifies in most studies), current use of antibiotics, puncture or bite wounds, underlying tendon or bone involvement, wounds more than eight or nine hours old, and grossly contaminated wounds. We still see a fair number of lacerations that wouldn't fall into any of these categories, but keep in mind that the safety of tap water hasn't really been evaluated in these patient populations, so caveat utilitor, if you know what I'm saying.
No doubt some of you were concerned that I failed to address the question of irrigation pressure. We've all been taught that effective irrigation requires something like 8 psi of minimum pressure. Like many things we've been taught, the evidence backing this recommendation is weak, but it has at least a surface logic and we should give it the old college try if we're going to wash out a wound. Standard syringe techniques with an 18 or 19 gauge angiocatheter can get us pressures in that range. (J Enterostomal Ther 1985;12:27; Am J Emerg Med 1995;13(3):265.)
The Valente study measured the pressure of the tap water and found that it ranged from 50-60 psi (converted from 3.52 to 4.22 kgf/cm2 as measured in their original article). This is in line with the measurements taken in the 1998 article by Moscati, et al., that found, “The water pressure was 45 psi regardless of whether it was measured at the end of the nozzle or at the end of the faucet with the nozzle removed.” The take-home point for any budding hydraulic engineers in the audience: Pressure from the tap blows syringe irrigation out of the water (pun very much intended).
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