In total, 104,469 catheter-hours (54,173 h in 584 COS and 50,296 h in 599 MOS) were recorded. The median dwell time was 137.1h for COS PIVCs and 96 h for MOS PIVCs (P = 0.001). Among PIVCs in place for ≥ 24 h, the median dwell time was 144.5h for COS PIVCs [95% confidence interval (CI) 123.4-165.6] and 99 h for MOS PIVCs (95% CI 87.2-110.8). Use of COS PIVCs reduced phlebitis rates by 29% (31 vs 45 cases/1000 catheter-days; P = 0.004). The probability that a MOS PIVC would last for 96 h was 79.9%, and the probability that a COS PIVC would last for 144 h was 80.4%. There were no significant differences in rates of bacterial colonization per 1000 catheter-days (51.1 COS vs 54.1 MOS) or CRI (5.76 COS vs 6.65 MOS). Nevertheless, there was a 20% relative risk reduction in CRI.