Irrigation solution: What’s in the water?

The evidence that supports the use of various irrigation methods with or without antibiotic additives is not convincing.

In a recent article reviewing different myths and legends in orthopedic surgery, Tejwani and Immerman surveyed members of the Orthopaedic Trauma Association and various community and academic surgeons on the use of antibiotics in irrigation solutions. They asked the surgeons if they were aware of any literature to support their practice of choice. They reported that 46% of the respondents regularly used antibiotics in the irrigation solution during surgery, and that this practice was less common among academic surgeons. However, the majority of academic and community surgeons who acknowledged knowing the literature regarding this topic reported not using antibiotic irrigation solutions.

Javad Parvizi

In a preliminary report of a larger study, Petrisor and colleagues surveyed a group of 984 international orthopedic surgeons on the use of fluid lavage in open fractures. The group was composed of surgeon members of the Canadian Orthopaedic Association and attendees of an AO international fracture course in Davos, Switzerland. In terms of the preferred type of irrigation solution for an open wound, 70.5% of the respondents said that they favor normal saline alone, 16.8% preferred saline with bacitracin, 6% used an iodine based solution and 1.3% used a soap/detergent solution.

Of note, 50.1% of the surveyed surgeons did not believe that bacitracin or soap solution were more efficient then saline alone, whereas the majority believed that chlorhexidine (46.3%) and iodine (44%) were more effective despite the numerous reports suggesting that these antiseptics may be toxic at the cellular level and may cause delays in wound healing.

In vitro studies

The differences in opinion in these two studies are not surprising considering the conflicting reports among the in vitro and animal studies in the literature and the scarcity of published human trials.

Wadih Y. Matar

In vitro studies both support the use of antiseptics, antibiotics or soaps in irrigation solutions and that these agents are not superior in removing bacteria from bone or metal surfaces.

Anglen and colleagues studied the efficacy of different irrigation solutions delivered through jet lavage to remove bacteria from three different surfaces: cortical bone, stainless-steel and titanium. The different solution included normal saline and solutions containing bacitracin, neomycin, or soap. The surfaces were coated with three different bacteria: Staphylococcus aureus, Pseudomonas aeruginosa, and Staphylococcus epidermidis.

After quantitatively culturing the specimens following lavage for any residual bacteria, they concluded that bacterial removal was influenced by the characteristics of the given surface, the bacteria itself and the irrigation solution.

They showed that the soap solution was superior compared to saline alone in removing S. aureus from all three surfaces as well as S. epidermidis from steel and titanium. However for the stainless steel surface, soap solution was not significantly different than antibiotic for S. aureus or P. aeruginosa. For titanium, soap was better than bacitracin for S. aureus but similar to the antibiotic for P. aeruginosa.

Soap superiority

The results for the bone surface varied the most: soap was once again better than bacitracin for S. aureus but similar to neomycin and saline, and as for S. epidermidis, there were no differences between the solutions. However, neomycin proved to be superior in removing P. aeruginosa from all three surfaces with some of these differences not reaching statistical significance.

The superiority of soap solution is believed to be due to its surfactant formation which disrupts the nonspecific early adhesion of the bacteria to the surface. This bond is thought to be due to nonspecific attachments which are gravitational, electrostatic and hydrophobic in nature. Surfactants, which have both a hydrophobic and a hydrophilic domain, lower surface tension and break down the hydrophobic and electrostatic forces disrupting the bacterial adhesion to the surface.

Furthermore, soaps are a group of surfactants that form micelles that surround the bacteria and prevent it from adhering to the surface and allowing it to be rinsed from the wound. In fact, this effect is further amplified with the use of jet lavage which has been shown to increase bacterial removal by a factor of 100 to 100,000 compared to low-pressure irrigation with a bulb syringe.

In vivo studies

Several literature reviews of the animal data on the use of antibiotic in irrigation solution show conflicting results often based on body cavity models which do not necessarily represent orthopedic surgery.

Anglen and colleagues developed a rat model with an orthopedic wound that was inoculated with S. aureus for a period of 15 minutes and then irrigated with either normal saline or soap solution. The animals were followed for signs of infection and subsequently sacrificed at 14 days.

The soap solution (benzalkonium chloride) proved to be superior to normal saline alone by lower number of culture-positive animals and number of deep wound and total positive cultures.

It is important to note, however, that the positive effects of irrigation with benzalkonium chloride were not confirmed when the wound was contaminated with P. aeruginosa. On the contrary, a higher number of positive wound cultures were identified and benzalkonium chloride was found to cause wound dehiscence and breakdown in 75% of the rats requiring the premature sacrifice of the animals.

These negative effects were eliminated – while maintaining a superior bacterial removal effect compared to normal saline – by sequentially washing the wound with benzalkonium chloride followed by castile soap and saline.

Low-pressure irrigation

The above results were not reproduced in the goat model by Owens and colleagues. Using a well-established complex musculoskeletal wound in the goat that was inoculated with P. aeruginosa (lux) – a genetically engineered luminescent bacteria allowing for quantitative analysis – and subsequently irrigated with one of four solutions: normal saline, bacitracin, castile soap, or benzalkonium chloride.

Immediately after the initial irrigation, bacterial counts were lower in all treatment groups with best results seen with the castile soap (13% of pretreatment level) followed by benzalkonium chloride (18%), bacitracin (22%), and saline solution (29%). However, at 48 hours, bacterial counts increased in all groups with the highest increase being in the castile soap group (120%) followed by benzalkonium chloride (94%), bacitracin solution (89%) and normal saline solution (68%).

In the second part of the study, pulsatile lavage was compared to bulb syringe irrigation with saline solution. They found irrigating with the pulse lavage caused a rebound to 94% of the original levels at 48 hours compared to 48% when irrigated with a bulb syringe. They concluded that low-pressure irrigation with saline solution may be the best choice for irrigation of contaminated wounds.

Human studies

Human data is restricted to a small number of anecdotal studies in the setting of elective surgery of the spine and upper extremity and a few prospective randomized studies based on often-criticized methodology.

Museru and colleagues performed a randomized controlled trial comparing isotonic saline, distilled water and boiled water in irrigating open fracture wounds. The reported infection rates were 35% for the isotonic saline group, 17% for the distilled water group and 29% for the boiled water group leading the investigators to conclude that the irrigation solution type did not influence the infection rate.

Anglen conducted a prospective randomized clinical trial comparing a bacitracin containing solution with a castile soap solution in lower extremity fractures. Four hundred patients were randomized and the mean follow-up was 500 days. There were no statistical differences in the infection rate or fracture healing between the groups. However, 9.5 % of the fractures in the bacitracin group went on to develop wound-healing complications compared to 4% in the soap group – a statistically significant difference.

He concluded that irrigation with antibiotic solution did not offer any advantages over soap solution and may have been deleterious to wound-healing. He cited potential problems with using antibiotics in irrigation solution as unnecessary cost, serious risk of toxicity/anaphylaxis and promotion of antibiotic resistance.

Despite being the most complete randomized prospective clinical trial in this field, this study has several limitations including problems with the randomization process, significant differences between the two groups, no control arm and the fact that it was limited to lower extremity fractures.

Not convincing evidence

The principles of dealing with an open fracture have long been established and dictate methods that are believed to reduce the risk of infection. These include: assuring tetanus prophylaxis, emergent treatment, intravenous antibiotics, meticulous debridement of contaminated soft tissues, removal of all foreign materials and reduction of the bacterial load by irrigation of the wound.

Despite the several proposed irrigation techniques, the evidence supporting their use including the use of additives in irrigation solutions is not convincing. Furthermore, questions regarding the appropriate volume, pressure and delivery system also need answering.

The latter further highlights the need to conduct and participate in the future studies such as the Fluid Lavage in patients with Open Fracture Wounds (FLOW) study as it may lower infection rates and hence their global consequences as well as aid us in the orthopaedic world in getting rid of one of our identified myths.

For more information:

• Wadih Y. Matar, MD, MSc, FRCSC, and Javad Parvizi, MD, FRCSC, can be reached at Rothman Institute of Orthopaedics at Jefferson, 925 Chestnut St., 2nd Floor, Philadelphia PA 19107; 267-399-3617; e-mail: parvj@aol.com.

References:

• Anglen JO. Comparison of soap and antibiotic solutions for irrigation of lower-limb open fracture wounds. A prospective, randomized study. J Bone Joint Surg (Am). 2005;877:1415-1422.
• Anglen JO, Apostoles PS, Christensen G, et al. Removal of surface bacteria by irrigation. J Orthop Res. 1996;142:251-254.
• Anglen JO, Gainor BJ, Simpson WA, Christensen G. The use of detergent irrigation for musculoskeletal wounds. Int Orthop. 2003;271:40-46.
• Museru LM, Kumar A, Ickler P. Comparison of isotonic saline, distilled water and boiled water in irrigation of open fractures. Int Orthop. 1989;133:179-180.
• Owens BD, White DW, Wenke JC. Comparison of irrigation solutions and devices in a contaminated musculoskeletal wound survival model. J Bone Joint Surg (Am). 2009;91(1):92-98.
• Petrisor B, Jeray K, Schemitsch E, et al. Fluid lavage in patients with open fracture wounds (FLOW): an international survey of 984 surgeons. BMC Musculoskelet Disord. 2008;23:9:7.
• Tejwani NC, Immerm-an I. Myths and legends in orthopaedic practice: are we all guilty? Clin Orthop Relat Res. 2008;466(11):2861-2872.