Infection

The literature has reviewed a number of preventative strategies employed to reduce catheter-related infection. They include: low nurse-patient ratio, maximal sterile barriers, use of topical ointments, appropriate catheter dressings, and type of skin antiseptics.

Nurse-Patient Ratio

The literature appears to be consistent in its support of an educational program and/or specialized team of individuals dedicated to the care of intravascular devices [15, 24, 25]. In a cohort study of surgical intensive care unit patients with CVC associated blood stream infections, the corresponding patient to nurse ratio was reviewed by Fridkin et al. [26]. They hypothesized that an increase in the patient to nurse ratio, in combination with an increase in the total parental nutrition use, may have placed time constraints that prevented the nurse from caring for the CVCs properly. During an outbreak of CVC blood stream infections a high patient to nurse ratio was identified. In a study by Maki [11] a decrease in infection rates associated with CVCs occurred with the implementation of vascular access teams. These reports indicate that increased time, care, and attention paid by individuals dedicated to a single task may result in fewer infectious complications.

Maximal Sterile Barriers

Use of maximal barriers and careful hand washing prior to and during the insertion of a CVC are reported to the most important steps in preventing catheter-related infections [11, 20, 27, 28]. A maximal sterile barrier involves wearing sterile gloves, a mask, gown, and using a large drape. Darouiche and Radd [15] reported a four-fold decrease in the rate of pulmonary artery catheter bacteremia and a more than six-fold decrease in the rate of CVC sepsis following the use of maximal sterile barriers during the insertion of CVCs.

Topical Ointments

Theoretically, the application of topical ointments should confer some protection against microbial invasion [11]. In the study by Levin et al. [29] where the treated group (n = 63) received povidone-iodine ointment with the dressing changes and the control group (n = 66) used dry dressings for CVC exit site care, there was a reported 93% relative reduction of septicemia in the treated group. In a comparative study of a polyantibiotic and iodophor by Maki and Band [30] (n = 827 catheters from 381 patients), the rates of catheter-related septicemia was too low to make a valid comparison. The conclusions were that the polyantibiotic offered some protection against catheter-related infection but only marginally.

Dressings

Microorganisms that colonize the skin are responsible for most of the infections that occur around catheter exit sites. Improper handling of the device by staff may also contribute to the infectious process. The dressings that cover the exit site could therefore have considerable influence on the incidence of nosocomial infection. The purpose of an intravascular site dressing is to prevent trauma to the catheter wound and the cannulated vessel as well as to prevent extrinsic contamination of the wound [19, 31]. Numerous studies have been carried out in an attempt to identify the most appropriate dressing for intravascular access sites.

Criteria for insertion site dressings includes: they should be sterile, capable of moisture prevention, allow visible inspection, cost-effective, easy to apply and fix to the insertion site, and easy to remove [32]. The traditional dressing is gauze, covered by non-sterile tape. It does not allow visible inspection but allows the passage of organisms when wet, and should be changed daily. This increases the amount of manipulation of the device and could potentially encourage contamination of the hub. The alternative to the gauze dressing is the transparent polyurethane dressing. Specific types of transparent dressings have been proven to be more effective in their physical properties, particularly moisture vapor transmission rates, oxygen transmission and cutaneous adherence [33]. Further, patients are permitted to shower with transparent dressings in place.

The disadvantage associated with transparent dressings is greater cost, difficult removal, poor adherence to the skin over the catheter, and leakage due to drainage from the exit site wound. To obviate the disadvantage of cost, these dressings are left in place for up to 7 days or longer. The concern is whether transparent dressings left on for prolonged periods of time increases the risk of catheter-related infection. The literature presents conflicting results. In the studies by Maki et al. [34]; Richardson [35]; Claeys and Degrieck [36]; Wille et al. [37]; and Besley [38], leaving the transparent dressings for 7 days did not increase the incidence of catheter-related infections when the OpSite 3000 transparent dressing was used. Most of these studies took place in an ICU setting with the study periods being less than 3 weeks in total. In a study by Bijma et al. [39], 206 CVCs were studied over a 7-month-period in a surgical ICU. During the study, transparent dressings were replaced by gauze dressings and colonization rates were greatly reduced (206 CVCs in 128 patients, p < 0.025).

Skin Antiseptics

Skin cleansing of the insertion site is regarded as one of the most important measures for preventing catheter-related infection. Disinfectant agents use alcohols, chlorine and chlorine components, and iodines. Commonly used disinfecting agents include povidone-iodine, chlorhexidine, alchohols, and electrolytic chloroxidizer.

Povidone-Iodine

Iodine solutions employ a wide microbiological activity when formulated with free iodine [16]. Povidone-iodine is the most widely used form of iodophor compound. The 10% solution is known as Betadine. It is frequently used in hospitals as a disinfectant. Iodophors are effective against most bacteria and viruses but less effective against fungi. It is not sporicidal and is inactivated by organic compounds such as blood and serum protein [40]. It is important to allow the skin surface to dry to achieve its effectiveness. The time recommended is 3-5 min. Further, povidone-iodine can be irritating to the skin causing skin breakdown thereby opening a portal for microorganisms.

Chlorhexidine

Chlorhexidine gluconate, a cationic bisbiguanide, was developed in England in the early 1950s and was introduced into the United States in the 1970s. It is a chlorophenol biguanide with a broad antimicrobial spectrum. It is thought that chlorhexidine produces enzymatic reactions within the cell that result in protein denaturation and inactivation of nucleic acids [16]. Chlorhexidine is active against many Gram-positive and to a slightly lesser degree Gram-negative bacteria. Chlorhexidine is supplied in various concentrations of 0.5% with 70% alcohol, 2%, and a 4% detergent. It has greater residual activity than alcohol alone and is not inactivated by the presence of blood or human protein [19, 38-40]. There is minimal absorption through the skin. Anaphylactic reactions with bronchospasms and generalized urticaria are very rare and are associated with use on mucous membranes. In a prospective, randomized trial by Fuchs et al. [41], three different methods of catheter exit site care were studied in a peritoneal dialysis population for 14 months. The solutions used included chlorhexidine gluconate and water, dilute sodium hypochlorite solution, and povidone-iodine. The study failed to demonstrate that one method of care was superior to another. In the prospective, randomized study by Mimoz et al. [42], chlorhexidine gluconate and 10% povidone-iodine were compared in all ICU patients during the 15-month study requiring a CVC or arterial catheter. The chlorhexidine solution was superior in preventing catheter colonization and catheter-related sepsis due to Gram-positive bacteria (5 vs. 20 [p < 0.001] and 2 vs. 10 [p 0.001], respectively), whereas the chlorhexidine was not superior in preventing Gram-negative infections (7 vs. 4 [p = 0.5] and 4 vs. 2 [p = 0.8], respectively). Maki [19] compared three antiseptics for disinfection of 668 central venous and arterial catheters. Chlorhexidine was associated with the lowest incidence of local catheter-related infection and catheter-related bacteremia in comparison to alcohol and povidone-iodine. Traore et al. [43] compared povidone-iodine to chlorhexidine in two groups of 22 healthy subjects and concluded that both antiseptics are equal in bactericidal activity at 0 time, 30 s, 3 min, and 2h. There is high alcohol content in the chlorhexidine solutions, which has damaging effects on some catheter materials, thereby restricting its use.

Alcohols

The majority of alcohol-based hand antiseptics contain isopropanol, ethanol, n-propanol, or a combination of these products. Ethyl alcohol (ethanol) and isopropol are not considered high-level disinfectants though they are frequently used to clean small surfaces such as rubber stopped vials. Alcohol is used as a disinfectant with rapid action against a broad spectrum of microorganisms. However, once evaporated, the alcohol has no long-lasting antimicrobial effect. They act by denaturing or altering the molecular structure of the bacterial proteins, destroying the cell. They are rapidly bactericidal, viricidal, and tuberculocidal but they do not destroy bacterial spores nor do they penetrate protein rich material such as blood [16]. Optimal concentrations range from 60 to 90%. Alcohol dries and irritates the skin. The combination of alcohol and iodine is used as a tincture which delivers rapid and sustained antimicrobial action, but the iodine often causes skin irritation and staining. The alcohol gel with 5% iodine has equal effectiveness as a high concentration of alcohol and is less irritating to the skin [44, 45]. In a study by Traore et al. [43], where an iodine alcohol solution and iodine scrub was compared to a chlorhexidine alcohol solution and chlorhexidine scrub, the results were comparable for all four groups.

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