Thirty-seven trials reporting 41 CVC comparisons (11,586 patients) were included. Concealment of allocation was reported as adequate for 14 trials and not adequate for six. Clinicians were reported to be blinded to allocation for 10 trials and not blinded for 20 trials. Seven trials reported both adequate concealment of randomisation and blinding of clinicians. The rate of follow-up ranged from 71% to 100%.
For the outcome CR-BSI, heparin bonded CVCs reduced the risk of infection by 84% (RR 0.16, 95%CI: 0.06, 0.43, χ2 P = 0.42), based on three trials (n=462), none of which reported both adequate randomisation and blinding. Antibiotic impregnated CVCs reduced the risk by 72% (RR 0.28, 95%CI: 0.15, 0.54, χ2 P = 0.65), based on seven trials (n=1747), three with adequate randomisation and blinding. The comparisons of CH-SS impregnated and silver-impregnated CVCs against standard CVCs showed a trend towards lower rates of infection in the impregnated CVC groups, but neither comparison reached statistical significance.
The only head-to-head comparison of impregnated CVCs to reach statistical significance was that for antibiotic impregnated against CH-SS impregnated CVCs, with lower rates of infection in the antibiotic impregnated group (RR 0.12, 95%CI: 0.02, 0.670, χ2 P = 0.48). This was based on two trials (n=812), one with adequate randomisation and blinding.
In terms of catheter colonisation, one small RCT showed a statistically significant benefit from heparin CVCs compared to standard CVCs (RR 0.42, 95%CI: 0.18, 0.99, n=32). CH-SS impregnated CVCs reduced the risk of colonisation by 42%, however the 16 trials (n=3,939) were found to be highly heterogeneous (RR 0.58, 95%CI: 0.43, 0.77, χ2 P<0.001). Only two of the 16 trials reported adequate randomisation and blinding. The six trials (n=1,357) comparing antibiotic impregnated CVCs against standard, found a 62% reduction in colonisation from antibiotic impregnation, however the studies were again highly heterogeneous (RR 0.38, 95%CI: 0.21, 0.71, χ2 P=0.0005).
For the head-to head comparisons of impregnated catheters, antibiotic impregnated CVCs were found to be significantly more effective than both silver impregnated (one trial) and CH-SS impregnated (two trials) catheters. CH-SS impregnated CVCs were also shown to be more effective at reducing catheter colonisation than heparin impregnated catheters (one trial).