The Attributable Mortality and Costs of Primary Nosocomial Bloodstream Infections in the Intensive Care Unit

Abstract

Primary nosocomial bloodstream infection (BSI) is a common occurrence in the intensive care unit (ICU) and is associated with a crude mortality of 31.5 to 82.4%. However, an accurate estimate of the attributable mortality has been limited because of confounding by severity of illness. We undertook this study to assess the attributable mortality and costs associated with an episode of BSI. Infected patients were defined as those who had an episode of BSI during the study period. Uninfected con- trol subjects were matched to the infected patients based upon a number of factors, including pre- dicted mortality on the day prior to infection. The main outcome measures were crude ICU mortality, length of stay, and costs. We found no difference in the crude mortality for the infected and the un- infected patients (35.3 and 30.9%, respectively, p 5 0.51). However, among survivors, the patients with nosocomial bloodstream infections did have excess length of stay (mean, 10 d; median, 5 d; p 5 0.007) and increased direct costs (mean difference, $34,508; p 5 0.008). After matching for severity of illness, we could not detect an association between primary nosocomial bloodstream infections and increased ICU mortality. We did find that primary nosocomial bloodstream infections increased ICU length of stay and costs. DiGiovine B, Chenoweth C, Watts C, Higgins M. The attributable mortality and costs of primary nosocomial bloodstream infections in the intensive care unit. AM J RESPIR CRIT CARE MED 1999;160:976-981. Primary nosocomial bloodstream infections (BSI) are associ- ated with excess mortality and hospital costs. The crude mor- tality for nosocomial bloodstream infections, estimated from a recent review of 3,077 patients, appears to have decreased from 51% in 1981 to 29% in 1992 (1). This estimate included all hospitalized patients, not just those in the ICU. Specific studies investigating the crude mortality for bloodstream in- fections in the ICU have estimated the crude mortality to be approximately 56%, ranging from 31.5 to 82.4% (2-5). Other studies have estimated that there are close to 4,500 deaths di- rectly caused by these infections yearly (6). Furthermore, pri- mary bloodstream infections are felt to increase length of stay (LOS) by 7.4 d, and increase charges by $3,517 per episode (1992 dollars) (6).