ObjectiveTo assess the infection potential of not routinely changing invasive monitoring kits and associated plasticware.DesignA prospective, observational study of microbiological contamination of a cohort of pressure monitoring infusion systems.SettingAdult intensive care units in a university tertiary care center.PatientsPatients who had invasively monitored arterial, central venous, or pulmonary artery catheters in place for ≥96 hrs without a change to the system were entered into the study.InterventionsFluid samples were obtained from the proximal stopcock of the monitoring kits every 24 hrs, beginning with a sample at 72 hrs and continuing until either the plasticware or catheter was changed or discontinued. Fluid samples were placed in tryptic soy broth and spread on blood agar plates within 24 hrs.Measurements and Main ResultsOf 451 intervals in which the system remained unviolated for ≥96 hrs except for sampling, no positive cultures were found. Of the 333 monitoring kits/lines in the study, four cultures became positive within 48 hrs of a violation of the system (flush bag change). Positive cultures were obtained from two different patients, one patient having positive fluid cultures from arterial, central venous, and pulmonary arterial kits. This bacterial growth would not have been eliminated with routine system changes as it occurred within a 48-hr timeframe.ConclusionsInvasive hemodynamic pressure monitoring systems including tubing and plasticware need not be changed routinely as these changes may cause a higher incidence of contamination due to increased violations of the systems. (Crit Care Med 1994; 22:1424–1430)