This study assessed the bacteriologic safety of room-temperature injectate used for cardiac output measurement in a surgical ICU, and compared its cost/benefit relationship to that of prefilled packaged syringes and a closed-loop injectate system. Ninety-five samples of injectate were obtained at four time intervals from staff-prepared syringes, and cultured for microbiologic growth. About 29% (27/95) of samples yielded bacterial growth, ranging from two colony-forming units to those too numerous to count. All positive samples contained skin flora, including coagulase-negative staphylococci and coryneforms. Additionally, five plates contained colonies of Gram-negative bacteria. Extended storage time increased the risk of contamination: 16.2% were contaminated within the first 24 h, whereas 45% were contaminated when stored for more than 72 h. Switching to a closed injectate system significantly (p< .001) decreased the incidence of contamination by 1.2%, and also allowed a cost savings of $1.52/patient.