Chest
Volume 100, Issue 1, July 1991, Pages 164-167
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Excess Mortality in Critically III Patients with Nosocomial Bloodstream Infections

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To determine the excess mortality attributable to hospital-acquired bloodstream infections, we applied the acute physiology and chronic health evaluation (APACHE) II classification to 34 critically ill patients with this complication. The study included primary bloodstream infections, defined by a positive blood culture at least three days after hospitalization, in the absence of any other apparent source of infection. The most frequent blood isolates included Staphylococcus aureus (39 percent), Gram-negative rods (24 percent), and Candida albicans (15 percent); the spectrum of blood isolates suggested that most infections were related to intravascular catheters. In a control group of intensive care unit patients (n=384), the death rate predicted by APACHE II was similar to the observed death rate (35.3 vs 37.8 percent). In a subgroup of control patients (n=34), chosen for APACHE II scores that matched the patients with bloodstream infections, predicted and observed death rates were also similar (53.1 vs 52.9 percent). For patients with bloodstream infections, however, observed mortality (82.4 percent) significantly exceeded the predicted value (54.1 percent, p=0.025). We conclude that critically ill patients who develop nosocomial bloodstream infections are at greater risk of death than patients with comparable severity of illness without this complication. The difference between the observed and predicted death rates, 28 percent, represents the excess mortality associated with bloodstream infection in critically ill patients.

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Setting

The Medical Service of the New York Veterans Administration Medical Center consists of 120 ward beds, six cardiac care unit beds, a 16-bed ward for care of patients with AIDS, and a 12-bed medical ICU. The medical ICU is staffed by three interns, two residents, a pulmonary fellow, and an attending physician, all of whom rotate at monthly intervals.

Data Collection

The study covered the period from July 1986, through June 1989. We identified 34 medical ICU patients from a computerized log maintained by the

Microbiology Data

The frequency of blood isolates is shown in Table 2. Of the six cases of C albicans fungemia, three were associated with total parenteral nutrition, and one each with acute myelogenous leukemia, an intracranial meningioma treated with glucocorticoids, and acquired immunodeficiency syndrome. Polymicrobial bloodstream infections were found in six (14.6 percent) cases; three cases of C albicans fungemia were polymicrobial, including Enterobacter cloacae (two) and Pseudomonas cepacia (one).

Mortality Data

The

Discussion

Bacteremia is the most frequently encountered nosocomial infection in critically ill patients.10 Prior studies have revealed that between 33 and 45 percent of nosocomial bacteremias occur in ICU patients who occupy less than 10 percent of hospital beds.11 This study was designed to determine the excess mortality attributable to nosocomial bloodstream infection in patients in our medical ICU. To overcome a problem found in other mortality studies, that is, the lack of an appropriate control

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Manuscript received October 8; revision accepted December 21.

Instructor in Medicine, New York University Medical Center.

Former Fellow in Pulmonary Disease and Critical Care Medicine, New York University Medical Center.

§

Associate Professor of Medicine, New York University Medical Center.

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