Infection Protection

Surgical irrigation and infection risk

by Cynthia T. Crosby

Infection Protection is a monthly column dedicated to education about infection control issues. This month’s column discusses infection risk associated with surgical irrigation. Every fourth issue includes a Q&A forum to answer questions you have about the infection control information presented here. If you have a question, please submit it to jakridge@hpnonline.com or call 941-927-9345 ext. 202.

Surgical site infections (SSIs) can be caused by both exogenous and endogenous bacteria. Exogenous bacteria often come from the patient’s skin but may also be introduced by staff or instruments contaminated with microorganisms. Endogenous bacterial contamination also occurs in patients who have pre-existing infections or during surgical access to areas of high bacterial content, such as the gastrointestinal tract.¹ Depending on the amount and type of bacteria in the patient’s body, surgical wounds are classified as clean, clean-contaminated, contaminated, or dirty and infected (Table 1).²

Surgical staff members follow several procedures to reduce the risk of surgical-related bacterial contamination, including practicing thorough skin antisepsis, following proper hand hygiene and barrier protocols, and administering prophylactic antimicrobial therapy. Wound irrigation also is used during many types of surgery to remove bacteria and foreign material after surgical access or tissue debridement. The methods used for surgical irrigation may actually contribute to infection risk, however. This article describes recent studies of surgical irrigation methods and infection risk, as well as irrigation solutions.

Irrigation methods

Commonly used surgical irrigation methods include high-pressure pulsatile lavage (HPPL), suction irrigation, bulb syringe irrigation, and low-pressure gravity flow.^3,4 Although the pressure applied during HPPL may be assumed to remove more contaminants, some surgeons express concern about potential tissue damage associated with this method.

To prevent unnecessary risk to patients, studies to evaluate the effectiveness of these surgical irrigation methods are often conducted in vitro using animal tissue. In one randomized in vitro study, HPPL, suction irrigation, and bulb irrigation were evaluated using bovine tissue.³ Test samples were contaminated with rock dust, while comparator samples were left uncontaminated. Samples were then incised and exposed to irrigation or no irrigation. Runoff from the irrigation was collected and analyzed for the presence of organic and inorganic material. Samples were also evaluated in blinded fashion for the presence of soft tissue damage after irrigation. Tissue samples irrigated using HPPL showed the highest rates of tissue damage compared to other samples. More organic material was removed from samples irrigated with HPPL compared to those irrigated using suction or bulb syringe; however, less inorganic contaminant was removed. In this study, HPPL was associated with the highest rates of tissue damage but with inferior removal of inorganic contaminants compared to the other irrigation methods. In addition, investigators proposed that HPPL may drive some contaminants deeper into tissue rather than removing them.

Another in vitro study compared HPPL to low-pressure gravity flow irrigation.⁴ Ovine tissue was contaminated with fluorescently stained Staphylococcus aureus and subjected to irrigation. Tissue specimens were categorized based on orientation across or in line with muscle fibers. HPPL irrigation caused increased depth of bacterial penetration compared with low-pressure gravity flow (Figure 1). Also, tissue irrigated with HPPL had higher numbers of microbial counts after irrigation compared to tissue irrigated with low-pressure gravity flow. HPPL was associated with deeper penetration of bacteria and higher bacterial retention in soft tissue compared to low-pressure irrigation.

HPPL was also compared to pulsatile low-pressure lavage (PLPL), bulb syringe irrigation, and manual rinsing with brush cleaning on human bone tissue.5 This study was conducted to evaluate methods for cleansing bacterially contaminated bone tissue and to assess the risk of bacterial seeding in deep bone layers. Human femoral heads were contaminated with Escherichia coli and then cleansed with one of the four methods described. Bacterial counts were quantitatively determined at depths of 0 to 1 cm, 1 to 2 cm, and 2 to 3 cm. Both HPPL and brush cleaning were significantly more effective for surface cleaning than PLPL or bulb syringe irrigation. Bacterial contamination at various bone depths was significantly higher for HPPL and PLPL, however. This study demonstrated that brush cleaning was as effective for surface cleaning as HPPL but had lower risk of bacterial bone seeding in deep bone layers.

Legend:
HPPL was associated with increased depth of bacterial penetration compared to low-pressure gravity flow irrigation in ovine muscle tissue.

Additional study of high-fluid-pressure surgical instruments is needed as products enter the market. Recently the Versajet™ Hydrosurgery system (Smith&Nephew; Australia) was introduced into the U.S. market. The Versajet system uses high-pressure saline for wound debridement.6 Studies suggest that this product is particularly useful for burn wound excision in small, delicate areas, such as eyelids, digits, and web spaces.^7,8 In one study, patients were evaluated for clinical efficacy of burn wound debridement using the Versajet system, which was easier to use to treat mid-partial thickness burns in areas like the face, hand, and foot than conventional surgical tools.⁸ As products such as this one are used more extensively, surgeons and purchasing decision-makers are advised to balance the effectiveness of these tools against potential infection risk.

Irrigation solutions

Saline solution is generally used for wound irrigation. Although it would seem logical to use an antisepsis solution to inhibit microbial growth, some antisepsis solutions have been reported to impede wound healing.⁹ In a recent study of spinal surgery, however, diluted povidone-iodine was compared to saline for irrigation in lumbosacral posterolateral fusion surgeries.⁹ A total of 244 surgeries were evaluated. In half, 0.35% povidone-iodine solution followed by normal saline solution was used for irrigation; in the other half, normal saline alone was used. No infection occurred among patients in the povidone-iodine group, compared to six infections in the saline only group. The use of povidone-iodine was not associated with negative effects on bone fusion rate, wound healing, or functional outcome measures compared to saline.

An animal study evaluated chlorhexidine gluconate for closed postoperative peritoneal lavage to treat intra-abdominal infection.¹⁰ Infection was produced in mice by cecal ligation and puncture. Animals were divided into groups and either had no lavage or periodic lavage with chlorhexidine, cefoxitin, or lactated Ringer solution. Study endpoints included mortality and bacterial counts obtained from peritoneal fluid and biopsy specimens. The decrease in mortality rates with chlorhexidine lavage was statistically significant at 37% compared to 71% among the control group (no lavage). There was no survival benefit with the other lavage solutions used. Chlorhexidine also produced a statistically significant reduction in bacterial counts. Closed postoperative peritoneal lavage with chlorhexidine might be useful for the treatment of intra-abdominal infection.

Another animal study evaluated the use of human immunoglobulin G (IgG) compared to saline for irrigation of spinal wounds to prevent methicillin-resistant Staphylococcus aureus (MRSA) infection.¹¹ Infection was determined by clinical signs (e.g., swelling, erythema, etc.) and by bacterial counts from biopsied tissue and bone sites post-mortem at 7 and 27 days. Clinical signs of infection were reduced among sites irrigated with IgG, and bacterial counts were lower after IgG irrigation compared to saline. The use of IgG produced no significant differences in healing compared to saline and is proposed for local wound irrigation as supplementary prophylaxis against MRSA-associated infection.

Conclusion

Wound irrigation is necessary during surgery to remove bacteria and foreign material from wounds. However, the use of high pressure irrigation is not recommended because it can cause tissue damage and may increase risk for bacterial contamination. Additional study is needed to determine the optimal irrigation method for various types of surgery.

Although saline is still considered the standard solution for surgical wound irrigation, other solutions may provide benefit in selected cases. Diluted povidone-iodine has been associated with reduced infection risk in a small number of spinal surgeries. Chlorhexidine significantly improved survival rates and reduced bacterial counts in intra-abdominal infection in an animal model. IgG may provide additional inhibitory effects against MRSA, although additional study in human patients is needed.

A conservative approach to surgical irrigation is recommended until additional data are available. HPN

Acknowledgement:

The author wishes to acknowledge Catherine M. Jarrell for her assistance in developing this article.

References:

1.Meakins JL, Masterson BJ. Prevention of postoperative infection. ACS Surgery. 2003. WebMD, Inc. Available at: www.medscape.com. Accessed on June 27, 2006.

2.Report of an Ad Hoc Committee of the Committee on Trauma, Division of Medical Sciences, National Academy of Sciences—National Research Council. Postoperative wound infections: the influence of ultraviolet irradiation of the operating room and of various other factors. Ann Surg. 1964;160(suppl):1-192.

3.Draeger RW, Dahners LE. Related Traumatic wound debridement: a comparison of irrigation methods. J Orthop Trauma. 2006;20(2):83-88.

4.Hassinger SM, Harding G, Wongworawat MD. High-pressure pulsatile lavage propagates bacteria into soft tissue. Clin Orthop Relat Res. 2005;439:27-31.

5.Kalteis T, Lehn N, Schroder HJ, et al. Contaminant seeding in bone by different irrigation methods: an experimental study. J Orthop Trauma. 2005;19(9):591-596.

6.Data on file, Smith&Nephew, Melbourne and Sydney, Australia. Available at: http://wound.smith-nephew.com/AU/node.asp?NodeId=3987. Accessed on July 7, 2006.

7. Klein MB, Hunter S, Heimbach DM, The Versajet water dissector: a new tool for tangential excision. J Burn Care Rehabil. 2005;26(6):483-487.

8.Rennekampff HO, Schaller HE, Wisser D, Tenenhaus M. Debridement of burn wounds with a water jet surgical tool. Burns. 2006;32(1):64-69.

9.Chang FY, Chang MC, Wang ST, et al. Can povidone-iodine solution be used safely in a spinal surgery? Eur Spine J. 2006;15(6):1005-1014.

10.Bondar VM, Rago C, Cottone FJ, Wilkerson DK, Riggs J. Chlorhexidine lavage in the treatment of experimental intra-abdominal infection. Arch Surg. 2000;135(3):309-314.

11.Poelstra KA. Surgical irrigation with pooled human immunoglobulin G to reduce post-operative spinal implant infection. Tissue Eng. 2000;6(4):401-411.