To the Editor Dr Buetti and colleagues reported that replacement of peripheral intravenous catheters (PVCs) only when clinically indicated led to an increased risk of bloodstream infection (BSI) compared with routine replacement every 96 hours.1 Overall, their conclusion was supported by the data; however, at least 3 questions remain.
First, despite an impressive incidence rate ratio of 7.20 (95% CI, 3.65-14.22), a complementary absolute metric that paints a complete picture is missing. We extracted data from eFigure 2 in the Supplement1 to evaluate the dwell time per PVC (dividing PVC days per month by the number of PVCs inserted per month). The mean dwell time across all patients was 3.66 days. The absolute increase in BSI incidence rate after the policy change was 0.77 per 10 000 PVC days (0.9 per 10 000 in the intervention group minus 0.13 per 10 000 in the baseline group). Using the mean dwell time as a conversion factor, the absolute risk increase was 0.77 per 2732 PVCs (10 000 PVC days divided by 3.66 days) and the inverse yields the number needed to harm, which was approximately 3500 PVCs. Conversely, this means that to prevent 1 case of BSI, 3500 PVCs would need to be routinely replaced. In addition to patient discomfort, routine replacement increases consumption of resources (eg, device cost, employee time), yet surprisingly, does not affect thrombophlebitis rate.2,3 Taken together, the decision to adopt a routine rather than clinically indicated PVC replacement policy should be considered in the context of the high number needed to harm.