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Do chlorhexidine baths prevent healthcare-associated infections?

Healthcare-associated infections are a well-known problem, particularly in the critical care setting.¹ These infections will occur in up to 20% of intensive care unit (ICU) patients. They lead to increased lengths of stay and costs of care, as well as morbidity and mortality. In fact, hospital-acquired bloodstream infections (BSIs) are the most common cause of ICU morbidity, which are frequently associated with indwelling central venous catheters. The unsettling truth is that these infections, which are commonly caused by multi-drug resistant organisms and are therefore difficult to treat, are largely preventable.

A catheter-associated BSI occurs when the skin’s integrity is disrupted by insertion of the catheter and the organisms normally found on the skin are permitted to reach the blood and multiply, causing an acute infection.¹ The problem is that in the hospital setting a number of these normal organisms have developed resistance to antibiotics, and individuals in the hospital may become exposed to and colonized with a strain of these drug-resistant organisms, and subsequently infected with them. Therefore, proper sterile technique should be followed when central venous catheters are inserted. This includes disinfecting the skin with povidine, iodine, or more commonly, chlorhexidine. Chlorhexidine removes the organisms living on the skin and inhibits their rebound growth. It has been shown to reduce the incidence of catheter-associated BSIs and its use in this manner is recommended by the Centers for Disease Control and Prevention. Preventing patients from becoming colonized with drug-resistant organisms is a primary and important preemptive measure, particularly in high-risk ICU patients. In addition, skin asepsis, or source control, will reduce the risk of horizontal transmission between patients and healthcare workers and subsequently more patients. Current strategies to prevent horizontal transmission of resistant organisms rely on prompt identification of colonized patients, initiation of and compliance with contact precautions, and proper handwashing. Despite these recommendations, MRSA and VRE infections continue to increase.

A recently published study sought to determine whether the daily use of chlorhexidine baths in the ICU would reduce the incidence of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) colonization and BSIs.¹ The study was conducted in 6 ICUs at 4 medical centers which at baseline already utilized active surveillance culturing (ASC) from the anterior nares for MRSA; 3 of the ICUs also used ASC from the perirectal area for VRE. The ASCs were obtained within 48 hours of admission and then weekly and/or on discharge. Patients with a history of MRSA and/or VRE or a positive ASC were placed on contact precautions. The study utilized a before-and-after interventional design where for a baseline 6-month period all ICU patients were given daily bed baths using non-medicated soap and water, and for the intervention 6-month period, all ICU patients received daily bed baths using a chlorhexidine solution (4% chlorhexidine gluconate 4 ounces in warm water in a 6-quart basin) from the neck down. Standard prevention measures were in place, including the use of alcohol-based hand sanitizers; however, no other interventions were implemented during the study period, including routine mupirocin for decolonization.

A total of 5043 patients were included and 11,333 ASCs were obtained (85% of admissions, 92% of patients with stay >48 hours).¹ The change in mean incidence of MRSA and VRE colonization and bacteremia were calculated using Poisson regression. The null hypothesis was that the incidence rates during the baseline period and the intervention period were equal. The following definitions were established:

Acquisition of MRSA decreased 32% from the baseline to intervention period (incidence density: 5.04 vs. 3.44 cases/1000 eligible patient days, p=0.046).¹ The majority of MRSA cases were identified from nasal cultures (71%), followed by lower respiratory tract (20%), wound (5.5%), and blood (1.8%). The risk of MRSA acquisition was significantly lower in patients with chlorhexidine baths overall (RR 0.6637, p=0.024) and in patients with longer ICU stays. In fact, MRSA acquisition in patients with ICU stays >10 days was 4.37% with chlorhexidine baths vs. 9.93% during the baseline period (RR 0.58, 95% CI 0.351 to 0.968, p=0.02). Eight cases of bacteremia occurred during the baseline period vs. 5 cases during the intervention period.

Acquisition of VRE decreased 50% from baseline to intervention period (incidence density: 4.35 vs. 2.19 cases/1000 eligible patient days, p=0.008).¹ Time series models demonstrated that VRE incidence immediately decreased by 1.44 cases/1000 patient days upon the introduction of chlorhexidine baths (p=0.19). Incident VRE bacteremias decreased from 33 in the baseline period to 9 in the intervention period, a 73% reduction (2.13 vs. 0.59 cases/1000 patient days, p=0.0006). In addition, 16/270 (5.92%) colonized VRE patients developed VRE bacteremia during the baseline period vs. 4/226 (1.77%) during the intervention period (RR 3.35, 95% CI 1.13 to 9.87, p=0.035) suggesting that reductions in colonization led to the reductions in BSIs. Time series models demonstrated an increasing rate of VRE bacteremias in the baseline period which decreased in the chlorhexidine period, resulting in a 78% decrease (p=0.02) in VRE bacteremia attributable to chlorhexidine (decrease of 2.11 cases/1000 patient days).

The possibility of certain confounders explaining the reduction in MRSA or VRE acquisition could be excluded; for instance, the mean monthly prevalence rates among admissions was similar between baseline and intervention periods (MRSA: 22.80 vs. 21.80 and VRE: 17.97 vs. 16.75 cases/1000 patient days).¹ Also, the percentage of patient days occupied by patients with prevalent MRSA or VRE was similar in both baseline and intervention periods (MRSA: 14% for both and VRE: 9.283% vs. 8.097%, p=0.3). Time series models demonstrated that MRSA and VRE incidence slightly decreased during the baseline period, a trend furthered in the chlorhexidine period and resulting in a 25% decrease in the incidence of MRSA and a 45% decrease in the incidence of VRE in the intervention period attributable to chlorhexidine (MRSA: decrease of 0.66 and VRE: decrease of 1.51 cases/1000 patient days).

The authors concluded that daily chlorhexidine baths in ICU patients significantly reduced MRSA acquisition (32%), VRE acquisition (50%), and VRE bacteremias (73%), as well as the rate of VRE bacteremias in colonized patients (44%).¹ The stable MRSA and VRE prevalence throughout the study indicated that the planned intervention was additive to any realized benefits that an ASC program had established, and that the findings are not likely related to changes in culture technique, ascertainment, patient mix, or other potentially confounding variables. In addition, this intervention is neither difficult nor costly, making it one important adjunct measure to reduce MRSA and VRE acquisition and ensuing healthcare-associated BSIs.

While this study provides important information, it has several limitations; for example, lack of randomization and a before-and-after study design.¹ Individual patient data were not collected to any sufficient detail; certain patient characteristics may have affected the risk for acquiring MRSA or VRE such as previous or current antimicrobial use and compliance with proper handwashing techniques in the ICUs. In an attempt to minimize localized effects, the study used 6 ICUs in 4 different locations. To minimize the influence of potential confounders such as changing MRSA and VRE prevalence, the study evaluated the data using several methods including regression modeling. The results were consistent across the ICUs.

One concern with the use of frequent chlorhexidine baths is the possible development of resistance. Unfortunately, this study did not examine isolates for resistance patterns. Other similar studies, however, did not find a problem with chlorhexidine resistance. In fact, this is rare with staphylococci and enterococci; minimum inhibitory concentrations (MICs) are reportedly 0.2 to 3 mcg/mL (0.00002% to 0.0003%) and 1 to 6 mcg/mL (0.0001% to 0.0006%), respectively. Additionally, the resistance mechanism used by these organisms confers only a 2.5-fold increase in MICs to chlorhexidine (0.8 to 2 mcg/mL), well below concentrations of commercial products. Chlorhexidine resistance has been reported with gram-negative organisms, including Pseudomonas, Burkholderia, and Serratia. Although data were not reported, the authors of this study stated that they did not observe an increase in gram-negative bacteremias or fungemias. Because the potential exists, however, this could become a concern with widespread chlorhexidine use.

One commentary on this study concedes that the scientific rationale for daily chlorhexidine baths is convincing, since chlorhexidine is anti-bacterial while soap is not.² The study adds to the existing body of evidence since it examined a clinical endpoint, bacteremia, rather than just bacterial colonization as had been done in the past. This study has practical implications, particularly in institutions with a high rate of VRE colonization and bacteremia. On top of traditional infection control strategies, it would be prudent for such centers to implement daily chlorhexidine baths in ICU patients. Once instituted, colonization and infection rates should be closely monitored to determine the value of this practice. Chlorhexidine 2% solution should be used, with care being taken to avoid the eyes and areas of disrupted skin integrity.

Studies such as this are becoming more important in light of the recommendations made by the Centers for Medicare and Medicaid Services (CMS) and the list of Serious Reportable Adverse Events from the National Quality Forum (NQF).³ The NQF is a private, national organization that sets the primary consensus standards for federal purchasers and quality oversight organizations, among others.⁴ The NQF endorses national voluntary consensus standards for the reporting of healthcare-associated infections. Providers and purchasers are increasingly interested in healthcare-associated infection rates as many states have implemented reporting requirements and this information is frequently made public. Intravascular catheters and bloodstream infections are one of the primary focus areas.

The NQF’s Never Events are defined as medical errors of concern to the public and healthcare professionals, clearly identifiable and measurable (i.e. reportable), and with a risk of occurrence significantly influenced by institutional policies and procedures.⁵ Hospitals are required by CMS to report whether or not claims for selected conditions at discharge were present on admission. Among this expanding list of conditions are vascular-catheter associated infections. Many states refuse payment by utilizing the NQF list of Never Events or the medical necessity process. To avoid payment liability for hospital-associated events and link payment to performance, states may create individual policies that cover some or all of the NQF Never Events.

For prevention of catheter-related bloodstream infections, the NQF endorses a central venous catheter insertion protocol, stewarded by the American Medical Association’s Physician Consortium for Performance Improvement.⁶ Central venous catheter insertion guidelines are followed, including all elements of maximal sterile barrier technique. These include cap, mask, sterile gown, sterile gloves, and a large sterile sheet, as well as hand hygiene and 2% chlorhexidine for cutaneous antisepsis.

In conclusion, the study presented was able to demonstrate that introduction of daily chlorhexidine baths in the ICU was associated with a significant reduction in MRSA and VRE acquisition and bacteremia. A relatively simple intervention, skin disinfection with chlorhexidine enhances barrier precautions to prevent horizontal transmission from colonized patients. Catheter-associated bloodstream infections are considered a serious risk to patient safety by the CMS and NQF and are included on the list of Never Events. Additionally, these hospital-acquired infections are preventable with proper institutional policies and procedures. Therefore, reimbursement may be withheld for claims of this nature, providing further impetus for adherence to infection control recommendations.