In a European multicenter study, up to 63 % of all surgical patients required an intravenous device insertion for intravenous access1,2. The main reasons for this intervention are drug administration, parenteral nutrition, fluid replacement, and hemodynamic monitoring. However, catheter-related infection can be a serious complication, leading to increases in mortality, hospital stay, and medical costs.2 On average, approximately 850000 catheter-related infections (CRI), and >50000 CR-BSI are annually reported in the United States with mortality rates ranging from 14% to 28%3–7. Similar results were reported in the National Nosocomial Infections Surveillance (NNIS) System Report (Data Summary from January 1992 to April 2000, issued June 2000)8. Potential risk factors for CRI are catheter type (single versus multi-lumen), frequency of port manipulations, catheter care, underlying disease, catheter indwelling time and localization of the catheter9. Efforts to decrease colonization and catheter-related blood stream infection have included aseptic insertion technique, proper catheter care, Teflon cuffs, flushing of the catheter with antibiotic solutions, administration of prophylactic systemic antibiotics and use of antibiotic coated and antiseptic impregnated catheters9. Silver has long been known to have antimicrobial properties. According to Hippocrates, the father of modern medicine, silver had beneficial healing and anti- disease properties. Interest in the antiseptic property of silver decreased because of the proliferation of antibiotics. However, with the emergence of multiple drug resistant strains of bacteria, there has been a renewed interest in silver. Studies have been done to determine the efficacy of silver impregnated catheters in reducing the rates of catheter related infection but results so far have been inconclusive. Two studies found no significant difference in the incidence of catheter related infection among high risk patients between silver iontophoretic catheters and control catheters10 while other studies have demonstrated increased efficacy of silver impregnated catheters in reducing the incidence of CR-BSI11-12. The above study was conducted to compare the incidence of CR-BSI in surgical patients following insertion of silver impregnated catheters versus conventional catheters.

Study place-The study was conducted at the Christian Medical College, Ludhiana, Department of General Surgery from 1st November 2009 and 31st May 2011. Study design-Prospective observational comparative study. Inclusion criteria- All surgical patients requiring central venous cannulation and willing to give written informed consent. Exclusion criteria- Patients allergic to silver, anatomic defect or skin lesions at the potential site of insertion, and unwilling to give written informed consent. Sample size-The sample size taken for this study was 400 patients. Data analysis- Statistical analysis was done using appropriate tools and tests of significance (SPSS 16.0). Data was analyzed and entered into Microsoft Excel sheet. Ethical considerations- All the necessary ethical permissions were taken from the Institutional Ethical Committee of the respective institution. Valid written informed consent was obtained from the participants. Patients were randomly assigned to undergo insertion of triple lumen central venous catheters either in standard version (non-modified; standard group) VYGON Multicath 3®) or silver impregnated (VYGON Multicath Expert®). A computer-generated random list with varying block size was generated which informed whether to use a modified or non-modified catheter. Documentation was done in patient’s file and study database. The insertion site was equally distributed between both study groups. Aseptic precautions were used. The insertion site was scrubbed with 10% Povidone-Iodine; excess solution was wiped from the site with sterile gauze. Post procedure chest X-ray was done to confirm correct placement of the catheter. Every 48-72 hours, the insertion site was recleansed with antiseptic solution (10% Povidone-Iodine), covered with sterile transparent (Tegaderm®) dressing, taped securely and inspected for signs of infection. The inserted central venous catheters were in place until they were no longer medically needed or an undesired event occurred, e.g. assumed catheter-related infection or catheter occlusion. The decision for CVC removal was made by the attending physician, either when it was no longer required or when a suspected CR-BSI occurred. The catheter was removed carefully. One 3 cm long segment was aseptically cut with sterile scissors. During removal, the site of catheterization was inspected for clinical signs of infection such as redness, induration/swelling, purulent secretion, and pain. No topical antiseptic was applied to the insertion site before CVC removal. The rate of CVC colonization among surgical patients and distribution among various age groups was studied and analyzed. Association of risk factors, such as duration of catheterization, co-morbid state (Diabetes mellitus, Hypertension) and total leukocyte counts (TLC) on removal of catheter were analysed.

Table no. 1: Rate of central venous catheter related infection (Conventional and Silver Impregnated) Cases No. %age Central line days Conventional CVC Colonization 92 46.0 65.0/1000 Silver Impregnated CVC Colonization 96 48.0 68.6/1000 The rate of Central venous catheter colonization in the conventional CVC arm was found to be 46% (n=92) or 65.0/1000 central line days. While in the silver impregnated CVC arm was found to be 48% (n=96) or 68.6/1000 central line days. Table no. 2: Distribution of patients according to number of catheter days in relation to CRBSI Catheter Days CRBSI Conventional CVC Arm(n=6) CRBSI Silver Impregnated Arm (n=7) No. %age No. %age Upto 5 3 50.00 4 57.14 6-10 2 33.33 2 28.57 11-15 1 16.66 1 14.28 16-20 0 0.00 0 0.00 >20 0 0.00 0 0.00 Mean 8.33 7.85 SD 6.65 6.60 p-value 0.991988 Out of the 6 cases of CRBSI in the conventional CVC arm group, 50% of the patients developed infection in the first five days of catheter insertion, 33.33% patients in 6-10 day’s duration and 13.66% patients in 11-15 day’s duration of catheterization. Out of the 7 cases of CRBSI in the silver impregnated arm group, 57.14% of the patients developed infection in the first five days of catheter insertion, 28.57% patients in 6-10 day’s duration and 14.28% patients in 11-15 day’s duration of catheterization. The mean duration of catheterization was found to be 8.33±6.65 days in the conventional CVC arm group and 7.85±6.60 days in the silver impregnated CVC arm group. On statistical analysis, the p-value obtained of difference in CRBSI in conventional CVC arm group and the silver impregnated CVC arm group was not significant. (p=0.9919) Table no. 3:Co-morbid state of patients according to CRBSI Co-morbid state CRBSI Conventional CVC Arm (n=6) CRBSI Silver Impregnated CVC Arm(n=7) No. %age No. %age Diabetes Mellitus 3 50.00 4 57.14 Hypertension 3 50.00 3 42.86 p-value 0.995812 Out of the 6 cases of CRBSI in the conventional CVC arm group, Diabetes Mellitus was found in 50% patients and Hypertension was also found in 50% patients. Out of the 7 cases of CRBSI in the silver impregnated CVC arm group, Diabetes Mellitus was found in 57.14% and Hypertension in 42.86% patients. The p-value obtained of difference in CRBSI in conventional CVC arm group and silver impregnated CVC arm group was statistically insignificant. (p=0.9958) Table no. 4: Distribution of patients according to Total Leukocyte Count on removal of catheter in relation to CRBSI Total Leukocyte Count on removal of catheter CRBSI Conventional CVC Arm (n=6) CRBSI Silver Impregnated CVC Arm (n=7) No. %age No. %age Significant (>10,000 mm3) 6 100.00 7 100 Insignificant (≤10,000 mm3) 0 0.00 0 0.00 p-value 0.262718 Total Leukocyte count was found to be raised in all the patients of CRBSI in both the groups. On statistical analysis, the p-value obtained of difference in CRBSI in conventional CVC arm and silver impregnated CVC arm was not significant. (p=0.2627) Table no. 5: Distribution of patients according to Fever on removal of catheter in relation to CRBSI Fever on removal of catheter CRBSI Conventional CVC Arm (n=6) CRBSI Silver Impregnated CVC Arm(n=7) No. %age No. %age Yes (>98.40 F) 4 100.00 7 100 No 0 0.00 0 0.00 p-value 0.614865 Fever on removal of catheter was found in all the patients of CRBSI in both the arms. On statistical analysis, the p-value obtained of difference in CRBSI conventional CVC arm and CRBSI silver impregnated CVC arm was not significant. (p= 0.6148) Table no. 6: Multivariate Analysis: Regression Analysis on CRBSI for both arms Variable Regression p-value 95% C.I. Odds Coefficient Lower Upper Ratio Constant -7.3700 0.007515 -14.364 -3.657 -9.011 Co morbid state -0.0196 0.257813 -0.118 0.041 -0.039 TLC on removal -0.0006 0.970588 -0.018 0.004 -0.007 Fever on removal 0.0310 0.098802 0.043 0.138 0.091 Catheter days -0.0028 0.193662 -0.019 -0.003 -0.011 R-square 0.1117 On logistic regression analysis of risk factors for catheter related blood stream infection, fever on removal of catheter was found to be independent predictor of CRBSI with slightly significant p-value of 0.09.

In the above conducted study, the rate of CRBSI was 5/1000 catheter days and CVC colonization was 68.6/1000 catheter days for the silver impregnated arm (Table 1). The rate of CRBSI in our study was found to be similar to the studies conducted by Bong et al.13 In the prospective study conducted by Bong et al. 13, 304 study catheters were inserted into 268 patients. Total duration of catheterization was 5449 days (median, 12 days/catheter). 128 silver catheters and 140 untreated catheters. Five cases (3.9%) of CRBSI occurred in patients who received silver catheters, compared with 5 cases (3.5%) in patients receiving control catheters. There was no significant difference in the incidence of catheter colonization or CRBSI between silver iontophoretic and control catheters. When the duration of catheter placement was taken into consideration, Kaplan-Meier analysis showed no significant difference in the risk of CRBSI between the silver iontophoretic catheters and the untreated catheters (p = 0.77). Our results were also supported by Dimmick et al.14 who found that the overall incidence of CRBSI was 3.6 episodes per 1000 catheter days. In our study, the rate of central venous catheter colonization was found to be 48% which is in agreement with a study conducted by Sachdev et al.15 on pediatric patients in Ganga Ram Hospital, New Delhi. Colonization rate was found to be 46.7% in their study. In another study conducted at St John’s Medical College & Hospital, Bangalore, by Rao et al.16 on 32 pediatric patients with Central venous catheter, the rate of CVC colonization was found to be 62.5%. In a prospective observational study of central venous catheters (CVC) carried out by Guillermo et al.17 in burn patients, colonization rates were 84% in CVC’s inserted near open wound and 47% in far from open wound. In above study, 50% of patients developed catheter related colonization in 6-10 day’s duration of catheterization and CRBSI was detected in 50 % of patients in 4-5 day’s duration of catheter insertion. Dimmick et al.14 & Chen et al.18 conducted studies on adult patients and showed significant increase in infection rate with the increase in duration of CVC use. Sachdev et al.15 also found that catheter tip was colonized earliest on day 5 and related bacteremia was detected on day 7 of insertion. In above study, raised total leukocyte count was found to be significantly associated with colonization of the CVC for both the arms. Raised total leukocyte count on the day of removal of catheter was found in 87.72% patients with CVC colonization in both the arms. No significant association of TLC was found with CRBSI. Sachdev et al.15 found that 40.7% of patients with abnormal TLC had CRBSI. In our study, statistically significant correlation of TLC was not found with CRBSI which may be due to the limited number of cases of catheter related blood stream infection in either arm. Co-morbid state such as diabetes mellitus and hypertension was found to be independent predictor of CVC colonization. Pawar et al.19 also found coexistent infections to be independent predictors of CRBSI. It was also seen that fever on the day of removal of catheter was found to be independent predictor of CRBSI. In case of CVC colonization,97.22 % patients had fever on the day of removal of the catheter. Pawar et al.19 also found that temperature was an independent predictor of CRBSI. In the study conducted by Sachdev et al.15, 78.3% of patients with CVC colonization and 43.4% with CRBSI had fever.

Hence, from the above study we can conclude that the significant higher cost of the silver impregnated catheters over the conventional triple lumen catheters and the demonstration of no significant reduction in CRBSI with the use of silver impregnated triple lumen catheters, cannot be justified. No patient related factors (co-morbid factors, total leukocyte counts) influenced the incidence of CRBSI in either group but fever at the time of catheter removal was found to be an independent predictor of CRBSI. According to the above study the silver impregnated CVC’s do not offer any advantage over conventional CVC’s.

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