Prognostic factors of mortality in patients with community-acquired bloodstream infection with severe sepsis and septic shock

Abstract

Purpose

The purpose of the study was to determine the independent risk factors on mortality in patients with community-acquired severe sepsis and septic shock.

Methods

A single-site prospective cohort study was carried out in a medical-surgical intensive care unit in an academic tertiary care center. One hundred twelve patients with community-acquired bloodstream infection with severe sepsis and septic shock were identified. Clinical, microbiologic, and laboratory parameters were compared between hospital survivors and hospital deaths.

Results

One-hundred twelve patients were included. The global mortality rate was 41.9%, 44.5% in septic shock and 34.4% in severe sepsis. One or more comorbidities were present in 66% of patients. The most commonly identified bloodstream pathogens were Escherichia coli (25%) and Staphylococcus aureus (21.4%). The proportion of patients receiving inadequate antimicrobial treatment was 8.9%. By univariate analysis, age, Acute Physiology and Chronic Health Evaluation II score, at least 3 organ dysfunctions, and albumin, but neither microbiologic characteristics nor site of infection, differed significantly between survivors and nonsurvivors. Acute Physiology and Chronic Health Evaluation II (odds ratio, 1.13; 95% confidence interval, 1.06-1.21) and albumin (odds ratio, 0.34; 95% confidence interval, 0.15-0.76) were independent risk factors associated with global mortality in logistic regression analysis.

Conclusion

In addition to the severity of illness, hypoalbuminemia was identified as the most important prognostic factor in community-acquired bloodstream infection with severe sepsis and septic shock.

Introduction

Sepsis is an important cause of morbidity and mortality, which accounts for about 2% of hospital admissions [1]. A small proportion of these cases progress to severe sepsis and septic shock, which account for 10% of admissions to intensive care units (ICUs) [2]. Bacteremia is the essential and fundamental pathophysiologic determinant of sepsis caused by bacteria, and every effort should be made to demonstrate bacteremia in patients with sepsis [3]. However, blood cultures were found positive in only 25% of severe sepsis and in 69% of septic shock [4].

Sepsis incidence is increasing at an estimated annual rate of 1.5%, and the growing numbers of sepsis patients who have organ dysfunction indicate that sepsis severity is also increasing [5]. Most bacteremias in ICUs are hospital-acquired infections, where the presence of patients with severe conditions and the need for multiple intravascular and other devices make such patients vulnerable to bloodstream infections. Only about 10% to 40% of bloodstream infections in ICUs are considered community acquired [6], [7], [8].

Despite advances in the care of critically ill patients, severe sepsis and septic shock continue to be associated with a dismal prognosis [9]. However, recently and based on the Surviving Sepsis Campaign guidelines for management of severe sepsis and septic shock [10], a slightly better prognosis for patients with these conditions has been observed [1], [11].

The outcome for critically ill patients with bacteremic sepsis has been associated with age, sex, severity of illness at onset of sepsis, comorbidities, nosocomial origin of the infection, and etiology [1]. Several studies have examined the institution of appropriate empirical antimicrobials with respect to mortality in sepsis with diverse results [7], [8], [12], [13], [14], [15], [16], [17], [18]. We have previously found no association between inadequate empirical antimicrobial treatment and the outcome in critically ill patients with sepsis [8]. However, most of our knowledge about prognostic factors in severe sepsis and septic shock are based on studies in which there is a mixture of community- and hospital-acquired infections or on studies in which only a proportion of patients with sepsis had severe sepsis or septic shock [7], [8], [13], [14], [15], [16], [17], [18]. Thus, the objective of this study is to determine the influence of clinical and microbiological characteristics, and empirical antimicrobial treatment on the outcomes of patients with community-acquired bloodstream infections with severe sepsis and septic shock.