Sunday, January 8, 2017

Does preoperative chlorhexidine scrub reduce or increase the risk of infection?

Preoperative Chlorhexidine Gluconate Use May Increase Risk for Surgical Site Infections after Ventral Hernia Repair

These authors sought to determine if preoperative chlorhexidine gluconate decreases the risk of 30-day wound morbidity in patients undergoing ventral hernia repair, the most common general surgery procedure in the United States

All patients undergoing ventral hernia repair in the Americas Hernia Society Quality Collaborative (AHSQC) were separated into two groups: one group received preoperative chlorhexidine scrub, and the other did not. A total of 3,924 patients identified within the AHSQC met inclusion criteria; of those, 2,209 (56.3%) received prehospital CHG scrub, while 1,715 (43.7%) did not receive prehospital CHG scrub.

The two groups were evaluated for 30-day wound morbidity including surgical site occurrences (SSO), surgical site infection (SSI), and surgical site occurrence requiring procedural intervention (SSOPI). While their registry collected data with regard to administration of chlorhexidine prior to surgery (yes or no), there was no specific variable which represented the route of administration (CHG wipes versus CHG 4% liquid soap), nor was there a standardized registry wide protocol which informed the instruction given to patients regarding how many applications are recommended.

Statistical analysis was performed using multivariate regression analysis and propensity score modeling. Multiple factors were controlled for statistical analysis including patient-related factors as well as operative factors.

After multivariate logistic regression modeling, the preoperative chlorhexidine scrub group had a higher incidence of SSO (OR 1.34, 95% CI (1.11-1.61) and SSI (OR 1.46, 95% CI (1.03-2.07)). After propensity score modeling, the increased risk of SSO and SSI persisted (SSO OR 1.39; 95% CI (1.15-1.70); SSI OR 1.45; 95% CI (1.011-2.072), respectively).

The authors conclude that prehospital chlorhexidine gluconate scrub appears to increase the risk of 30-day wound morbidity in patients undergoing ventral hernia repair. These findings suggest that the generalized use of prehospital chlorhexidine may not be desirable for all surgical populations.

Comment: The authors discuss the possible unintended consequences of chlorhexidine scrubs including the disruption of skin immune function related to the alteration of the skin’s local microbiome including the commensal and symbiotic bacteria (Staphylococcus epidermidis and Propionibacterium) located on the skin surface of a healthy individual. These organisms can modulate the innate immune response by producing modulins which selectively inhibit skin pathogens including S. aureus and Group A Streptococcus. Thus the skin surface is already equipped to protect itself against many of the same organisms that are currently eliminated or decreased in concentration by the use of chlorhexidine preoperative baths, including the most common pathogens causing SSI: Staphylococcus aureus and coagulase-negative staphylococci. It is possible that the use of chlorhexidine preoperatively may reduce the effectiveness of 'friendly' bacteria in resisting bacterial pathogens.

Do these results apply to orthopedics? This question was posed recently in an article: Does Preadmission Cutaneous Chlorhexidine Preparation Reduce Surgical Site Infections After Total Knee Arthroplasty?

This article asked does a preadmission chlorhexidine cloth skin preparation protocol decrease the risk of surgical site infection in patients undergoing TKA? They found that a prehospital chlorhexidine gluconate wipe protocol did appear to reduce the risk of periprosthetic infections after TKA, primarily in those patients with medium and high risk.

Obviously we have a lot to learn about infection prophylaxis. One way to approach the problem is to ask three questions: (1) For each joint surgery, what are the commonest bacteria to cause infection? (2) Are the bacteria found on the skin overlying that joint the same as those identified in question #1? (3) If the answer to question #2 is 'yes', what means do we have for reducing the risk that the skin bugs enter the wound? In the shoulder world, the answer to #1 appears to be Propionibacterium, the answer to #2 appears to be 'yes', and the answer to #3 includes the observation that the bacteria of interest lie in the dermis (rather than on the epidermis) so that surface application of antiseptics may not be helpful. 

Finally, it surely seems that that we are experiencing 'climate change' with respect to the problem of surgical site infections. The antibiotics we consume and those administered to the meat we eat, our use of 'antibacterial' soaps, our changing diet, and the devices we implant are progressively changing our relationship to the bugs around and in us. Keep in mind that the number of microorganisms in and on a health person is approximately equal to the number of human cells in that person. When we distort our biome, we change ourselves.


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