Chapter 146

Sepsis is a heterogeneous clinical syndrome that can be caused by any class of microorganism. Although gram-negative and gram-positive bacteria account for most sepsis cases, fungi, mycobacteria, rickettsiae, viruses, and protozoans can cause similar presentations. Microbial blood invasion is not essential to the development of sepsis.

The incidence of severe sepsis in the U.S. is 3.0 cases per 1000 population and 2.26 cases per 100 hospital discharges; 51.1% of patients with severe sepsis receive intensive care and an additional 17.3% undergo artificial ventilation in an intermediate care unit or are cared for in a coronary care unit.1 Incidence of sepsis increases >100-fold with age (0.2 per 1000 in children age 10–14 years to 26.2 per 1000 in those >85 years of age).1 Mortality is 28.6%, or 215,000 deaths nationally, and also increases with age, from 10% in children to 38.4% in those >85 years of age. Women have lower age-specific incidence and mortality, but this difference in mortality can be explained by differences in underlying disease and the site of infection. The average cost per case is $22,100, with annual costs reaching$16.7 billion nationally.1 The incidence is projected to increase by 1.5% per annum.

The incidence of sepsis and the number of sepsis-related deaths is increasing, although the overall mortality rate among patients with sepsis is declining.2 Sepsis is more common among men and among nonwhite persons. The rate of sepsis due to fungal organisms has increased by 207%, and since 1987 gram-positive bacteria have become the predominant pathogens.2 Organ failure contributes cumulatively to mortality; survival is improved among patients with fewer than three failing organs. The average length of hospital stay has increased, and the rate of discharge to non–acute care medical facilities has increased. Elderly patients are more likely to develop infections due to gram-negative organisms than are younger patients. Elderly patients are more likely than younger patients to have sepsis due to respiratory or GU tract infections. Pneumonia is the single most common cause of sepsis in the elderly.

Approximately 0.7% of ED patients present with suspected severe sepsis; more than two thirds of sepsis patients present initially to the ED.3 Over half of ED sepsis patients are ≥65 years of age. Approximately 17% of the presenting patients reside in nursing homes. One half of these patients arrive by ambulance, and mean length of stay in the ED is approximately 4.7 hours.

In the U.S. there are 42,364 cases of pediatric sepsis each year, or 0.56 cases per 1000 population per year.4 The incidence is highest in infants (5.16 per 1000), falls dramatically in older children (0.20 per 1000 in 10- to 14-year-olds), and is 15% higher in boys than in girls (0.60 vs. 0.52 per 1000, p <.001). Hospital mortality is 10.3%, or 4383 deaths nationally (6.2 per 100,000 population). Half of pediatric patients have underlying disease (49.0%), and over one fifth (22.9%) are low-birth-weight newborns. Respiratory infections (37%) and primary bacteremia (25%) are the most common infections. The mean length of stay for pediatric patients is 31 days and average cost per case is $40,600. Estimated annual total costs are$1.97 billion nationally.

Definitions of sepsis are regularly updated and now include definitions for pediatric cases5–8 (Table 146-1). The definitions provide a conceptual ...

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