ObjectiveTo compare the relationship between the time of pulmonary artery catheter replacement (4 days or 7 days after insertion) and the occurrence of catheter-associated infections.DesignOne-year prospective, randomized, controlled clinical trial.SettingSurgical and medical intensive care units at a 2,700-bed medical center.PatientsA total of 258 patients in critical condition who underwent pulmonary artery catheter insertion were recruited.InterventionsAll patients were randomized into two groups (4 days or 7 days) according to the length of time before the pulmonary artery catheter and pressure monitoring system were replaced.Measurements and Main ResultsOver a 12-month period, 331 catheters were inserted in 258 patients. In the per-protocol analysis, 98 patients (73.7%) in the 4-day group and 85 patients (68%) in the 7-day group were enrolled. Twelve patients (14.1%) in the 7-day group and 5 patients (5.1%) in the 4-day group (odds ratio, 3.06; 95% confidence interval, 0.94–10.48) had pulmonary artery catheter-tip colonization. Nine patients (10.5%) in the 7-day group and 7 patients (7.1%) in the 4-day group (odds ratio, 1.54; 95% confidence interval, 0.50–4.85) had bacteremia. In the 7-day group, pulmonary artery catheter-related bacteremia was found in only one patient (1.1%, 1.1 episodes per 1,000 catheter-days) compared with no patients in the 4-day group. The frequency of positive cultures from different sources between the 4-day and 7-day groups was not significantly different in the intention-to-treat analysis (p> .05).ConclusionsNo statistically significant difference was found for pulmonary artery catheter-associated infection when intervals of 4 or 7 days between insertion and replacement were compared. Patients with prolonged pulmonary artery catheterization must be carefully examined for signs or symptoms of infection. The time until pulmonary artery catheter replacement can be extended to 7 days if there is no evidence of catheter-related infection.