The increased risks of death and extra lengths of hospital and ICU stay from hospital-acquired bloodstream infections: a case-control study

Abstract

Objectives: Hospital-acquired bloodstream infections are known to increase the risk of death and prolong hospital stay, but precise estimates of these two important outcomes from well-designed studies are rare, particularly for non-intensive care unit (ICU) patients. We aimed to calculate accurate estimates, which are vital for estimating the economic costs of hospital-acquired bloodstream infections.

Design: Case-control study.

Setting: 9 Australian public hospitals.

Participants: All the patients were admitted between 2005 and 2010.

Primary and secondary outcome measures: Risk of death and extra length of hospital stay associated with nosocomial infection.

Results: The greatest increase in the risk of death was for a bloodstream infection with methicillin-resistant Staphylococcus aureus (HR=4.6, 95% CI 2.7 to 7.6). This infection also had the longest extra length of stay to discharge in a standard bed (12.8 days, 95% CI 6.2 to 26.1 days). All the eight bloodstream infections increased the length of stay in the ICU, with longer stays for the patients who eventually died (mean increase 0.7-6.0 days) compared with those who were discharged (mean increase: 0.4-3.1 days). The three most common organisms associated with Gram-negative infection were Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumonia.

Conclusions: Bloodstream infections are associated with an increased risk of death and longer hospital stay. Avoiding infections could save lives and free up valuable bed days.

Keywords: General Medicine (see Internal Medicine); Infectious Diseases; Intensive & Critical Care.

Figure 1

Four-state model to estimate the extra risk of death and extra length of stay due to a hospital-acquired bloodstream infection. The arrows represent hazards in a survival model. The extra risk of death was estimated using the HR of the hazard of death for infected patients (arrow A) and the hazard for susceptible patients (arrow C). The extra length of stay for those discharged alive was calculated by comparing the time taken to discharge for infected patients (arrow B) with the time taken to discharge for susceptible patients (arrow D).

Figure 2

Illustration of incidence density sampling for an infected case (patient E) and matched controls (patients A to C). The vertical dotted line shows the timing of infection. The dashed lines show the periods of hospital stay before infection. These times are discarded, as only times after infection are used to estimate the extra length of stay. The thicker solid lines show the time spent in the ICU. Adapted from Wolkewitz et al.