To determine risk factors for central venous catheter-associated bloodstream infections (CVC-BSI) during a protracted outbreak.

Case-control and cohort studies of surgical intensive care unit (SICU) patients.

A university-affiliated Veterans Affairs medical center.

Case-control study: all patients who developed a CVC-BSI during the outbreak period (January 1992 through September 1993) and randomly selected controls. Cohort study: all SICU patients during the study period (January 1991 through September 1993).

CVC-BSI or site infection rates, SICU patient clinical data, and average monthly SICU patient-to-nurse ratio.

When analyzed by hospital location and site, only CVC-BSI in the SICU had increased significantly in the outbreak period compared to the previous year (January 1991 through December 1991: pre-outbreak period). In SICU patients, CVC-BSI were associated with receipt of total parenteral nutrition [TPN]; odds ratio, 16; 95% confidence inter val, 4 to 73). When we controlled for TPN use, CVC-BSI were associated with increasing severity of illness and days on assisted ventilation. SICU patients in the out-break period had shorter SICU and hospital stays, were younger, and had similar mortality rates, but received more TPN compared with patients in the pre-outbreak period. Furthermore, the patient-to-nurse ratio significantly increased in the outbreak compared with the pre-outbreak period. When we controlled for TPN use, assisted ventilation, and the period of hospitalization, the patient-to-nurse ratio was an independent risk factor for CVC-BSI in SICU patients.

Nursing staff reductions below a critical level, during a period of increased TPN use, may have contributed to the increase in CVC-BSI in the SICU by making adequate catheter care difficult. During healthcare reforms and hospital downsizing, the effect of staffing reductions on patient outcome (ie, nosocomial infection) needs to be critically assessed.