Our study is the largest single-centre trial to validate TW as a safe and effective wound irrigant. It is the only study that was double-blinded and controlled for irrigation technique, pressures and solution volumes. We did not find any important differences in infection rates for wounds irrigated with either SS or TW. TW did have a trend to be superior to SS as a wound irrigant and at worst could result in a 0.4% increased infection rate compared with SS. This worst-case scenario is both statistically unlikely and clinically insignificant. As such, we feel that this adds to the existing literature, suggesting that TW is a safe and effective wound irrigant as compared with SS.8
There has been considerable debate regarding the potential advantages and disadvantages of irrigating wounds prior to closure with SS, as compared with TW. SS is most often used as a wound irrigant because it is an isotonic solution that does not interfere with the healing process or further damage tissue. It is available commercially as a sterile product.5
TW has the advantages of being readily available and less expensive.
Several other smaller trials have compared infection rates in acute soft tissue wounds that were sutured. Pooled results demonstrated a significant reduction in infection rates in wounds cleaned with TW, as compared with normal saline.8
A significantly higher infection rate in the saline group was reported by Angeras, but the irrigation technique and solution volumes were not standardised.13
Two trials measured infection rates in children and demonstrated no statistically significant difference in the infection rates when wounds were cleansed with either SS or TW.14
Dire and Welsh compared infection rates in wounds cleaned with different solutions (including SS) and found no statistical difference.11
Our study was not designed to identify why TW might be superior to SS as a wound irrigant. The hypotonicity of TW could disturb the osmotic potential of a bacterial cell, leading to cell death. It is also unknown what role chlorination of TW plays in its efficacy and safety as a wound irrigant. Future studies are needed to determine if there is an optimal range of chlorination content, or whether chlorine is required at all in TW used for wound irrigation.
It may be that the mechanism of cleansing (ie, mechanical irrigation) and the volume of solution used are the most important variables in preventing wound infection, rather than the irrigant solution. Wounds become infected when they contain more than 105
bacteria/gram of tissue.10
The threshold infective inoculum is reduced to 102
in the presence of dirt.23
High-pressure irrigation (>8 psi) with copious amounts of solution has been shown to be the single most effective method of reducing bacterial counts in wounds.,4–8
Potable TW in developed countries contains an insufficient number of bacteria to cause wound infections, and the few bacteria isolated from TW are not generally skin pathogens.18
Antimicrobial irrigating solutions have not shown any benefit over SS in reducing the incidence of wound infections.10
TW has both economic and environmental advantages over SS as a wound irrigant. TW is much less expensive than SS and is more readily available. At our institution, the cost of a 500 ml bottle of SS is $0.75; the patient charge is in excess of $10. With the number of lacerations treated each year, the use of TW could generate annual savings of $7.5 million for the hospitals and $100 million for patients. Irrigating accessible wounds directly under a faucet could result in additional cost savings by eliminating the need for sterile bowls, syringes and catheters. Others have investigated this technique and found equivalent rates of wound infections using TW as compared with SS for irrigation.14
From an environmental perspective, the use of TW would yield fewer plastic bottles to discard and has beneficial ramifications in situations where SS is not readily available. When water can be adequately disinfected, this would include disaster and humanitarian relief settings, field operations for the military and medical clinics, and hospitals in developing countries.
Strength and limitations of the study
The strengths of the study are its randomised design, control for technique of irrigation and volume of irrigant, successful blinding, relatively large number of subjects, and the fact that very few were lost to follow-up. A limitation of the study is that the primary measured outcome of wound infection was determined by subjective indicators of infection, such as erythema or gross exudate. Given the nature of the study, more objective measures such as bacterial counts, wound cultures or wound biopsy were not practical.
A second limitation was the six patients lost to follow-up during the study; five of these patients had wounds irrigated with SS and one had a wound irrigated with TW. This is a small number of patients lost to follow-up, and five out of six were in the SS group. Even if we assume that all these wounds became infected, it would only add further support to our conclusion that TW is a safe and effective alternative to SS as an irrigant solution.
Although we controlled for the volume of solution and the mechanism of wound cleansing, the temperatures of the solutions were not identical. The difference in temperature of the TW (38°C), as compared with SS (room temperature), may have been a factor. TW did not reach room temperature prior to initiating irrigation.
Telephone follow-up and self-reporting at the 1-month interval could have led to some misclassification by the patients conveying wound status, but the risk of misclassification should have been similar in both groups, and late complications subsequent to laceration repair are not common.