Introduction
The Guidelines for the Prevention of Intravascular Catheter-Related Infections published by the Centers for Disease Control (CDC) provide evidence-based recommendations for reducing the incidence of catheter-related bloodstream infections (CRBSIs).1 One of the recommendations concerns the use of transparent, semi-permeable polyurethane dressings. Compared to gauze, the transparency of polyurethane dressings provides the advantage of visual inspection of the catheter site without removing the dressing. Polyurethane dressings also do not need to be changed as often as gauze.

Polyurethane dressings and infection risk
An early study of transparent dressings compared to gauze conducted in 1987 demonstrated that cutaneous bacterial colonization and catheter-related infection were similarly low for both types of dressings. Neither type of dressing resulted in bacteremia.2 However, a meta-analysis of infection risk associated with various central venous catheter dressings revealed a slight increase of bacteremia and catheter sepsis associated with transparent dressings compared to gauze.3 A prospective, randomized study comparing gauze, conventional polyurethane transparent dressing and highly permeable transparent dressings used for pulmonary artery catheters also demonstrated that the highest risk of cutaneous bacterial colonization occurred under conventional polyurethane dressings. The risk for any infection among the three groups was extremely low, however, and there were no cases of CRBSIs. Permeable polyurethane was associated with a lower risk of colonization than conventional polyurethane.4

Several additional studies have been conducted to compare infection rates associated with various types of transparent polyurethane dressings and traditional gauze. Infection rates appear to be generally comparable,5 but moisture accumulation under conventional polyurethane dressings contributes to increased risk for cutaneous infection. Therefore, a higher moisture vapor transmission rate for transparent dressings was suggested,4 and several highly permeable transparent dressings are now available. Infection rate results from studies of these highly permeable transparent dressings vary. A review of several prospective studies suggests that there is no significant difference in clinical outcomes when highly permeable dressings are used,5 although one retrospective study demonstrated a significant 25% decrease in catheter-related infections associated with highly permeable dressings and associated cost savings of $69,814 due to the decrease in infection care costs and fewer hospital days.5,6 The CDC guidelines for catheter-related infections conclude that CRBSI rates do not differ significantly by type of dressing, and the choice of dressing material can be a matter of preference. In addition, the CDC guidelines describe advantageous effects of using chlorhexidine as part of the dressing regimen to reduce infection rates.1

Chlorhexidine dressings
A prospective study evaluated the efficacy of a chlorhexidine dressing in reducing microbial flora at catheter insertion sites. The dressing was constructed of a urethane sponge composite to which chlorhexidine gluconate was chemically bound. The dressing matrix was semi-permeable and non-occlusive with a higher vapor transmission rate than skin. An initial pilot study with 17 patients was conducted to determine the amount of catheter-site colonization that occurred with a control dressing. The pilot study was followed by a randomized study of 57 patients who received either a chlorhexidine dressing or a control dressing. The pilot study of the control dressing produced positive cultures in 29.4% of patients. Similarly, in the randomized arm of the study, the control group had a 29% rate of colonization. In contrast, the rate of infection among patients in the chlorhexidine dressing group was statistically significantly lower at only 3.8%. There were no adverse effects reported among patients in the chlorhexidine dressing group.7 Similar positive results have been demonstrated elsewhere. A prospective, randomized study evaluating the use of a chlorhexidine impregnated dressing (Biopatch; Johnson & Johnson, Arlington, TX) in 55 patients found positive cultures in 40.1% of the control group (11/27 patients) compared to 3.4% of the chlorhexidine group (1/29 patients).8 These results are illustrated in
(Figure 1.)

Cutaneous antisepsis with dressings
A "best practices" study of hemodialysis catheter care compared 2% chlorhexidine plus 70% isopropyl alcohol used with a transparent dressing to povidine with either gauze, transparent dressings, or transparent anti-microbial polyhexamethylene dressings. A total of 150 patients were evaluated for 30 days. All povidine dressing were changed three times per week. Chlorhexidine dressings were changed once per week unless they were soiled or stopped adhering. Staff and patients were surveyed regarding their preferences. Use of chlorhexidine dressings resulted in better staff and patient satisfaction, reduced nursing time, and decreased costs. The use of a 2% chlorhexidine/isopropyl alcohol skin antisepsis and transparent dressing was preferred for hemodialysis catheter care.9 A case report of an increase in CRBSIs in another hemodialysis center described an intervention designed to decrease infection rates. Staff members were educated about central venous catheter care, chlorhexidine replaced povidone iodine for cutaneous antisepsis, gauze was used instead of transparent dressings, and the use of antimicrobial ointments containing polyethylene glycol was discontinued. The 6-month intervention program decreased the CRBSI rate from 4.1 per 100 patient-months to1 per 100 patient-months. The use of optimal antisepsis contributed to the decrease in CRBSI rates.10

Cost savings with chlorhexidine
A randomized cost-benefit analysis including patients from all Philadelphia area hospitals and one academic center compared chlorhexidine dressings to standard treatment without chlorhexidine. The estimated annual cost benefit of using chlorhexidine dressings ranged from $275 million to approximately $1.97 billion, depending on baseline CRBSI rates, incremental costs of treating CRBSI, and the number of catheters used. Preventable mortality ranged from 329 to 3906 deaths annually, assuming nationwide use of chlorhexidine in the United States.11