Severe Sepsis Risk Depends More on Organ Dysfunction Mix Than on Age

Key Point

The increase in the identification of severe sepsis in recent years has less to do with the aging of the US population than with the type of organ dysfunction associated with severe sepsis.

NEW ORLEANS—Frank R. Ernst, PharmD, MS, and Stephen Stemkowski, MHA, of Premier Research Services in Charlotte, North Carolina, set out to examine the incidence of severe sepsis as it relates to age and International Classification of Diseases, Ninth Revision (ICD-9)-coded organ dysfunction. They found that advanced age is not accountable for as much of the increase in severe sepsis cases as is multisystem organ dysfunction (MOD). Their retrospective analysis of patients who had been treated for severe sepsis and discharged from 564 hospitals from 2002 to 2006 was presented at the American College of Chest Physicians’ 2007 Annual International Scientific
Assembly.

The findings from the current study partially support a 2001 study by Angus et al, in which severe sepsis incidence was predicted to increase by 1.5% annually due to the increasing age of the US population.However, the current findings emphasize the role of MOD in severe sepsis as previously found in a 1997 study of eight academic medical centers, where MOD was found to be a major cause of death in ICUs.

Defining severe sepsis as diagnosed infection with organ dysfunction and MOD as two or more organ dysfunctions, Ernst and Stemkowski discovered that while the proportion of total hospital discharges increased 12.4% during the five-year study period, the proportion of severe sepsis discharges rose even more—by 55%. This translated into a mean annual increase of severe sepsis discharges of 11.6%. On average, the proportion of patients 65 and older among cases of severe sepsis increased by 1.0% over the time period, while the proportion of cases involving MOD rose by less than 2.3%.

When severe sepsis discharges by organ dysfunction were analyzed, average per-year increases were noted for cases with cardiac (3.9%) and renal (9.0%) organ dysfunction, and decreases of 6.3% and 13.5% were seen in the rates of severe sepsis discharges with respiratory and neurologic organ dysfunction, respectively. Rates of severe sepsis discharges with hematologic and hepatic organ dysfunction annual increases remained relatively consistent at 1.5% and 1.8%, respectively. The authors concluded that changes in the mix of diagnosed organ dysfunctions may be associated with increasing severe sepsis identification more so than aging of the population.

The researchers expressed concern that their findings may be limited due to differing definitions of severe sepsis and MOD over time. They noted that early ICD-9 criteria of any infection plus an organ dysfunction diagnosis may overidentify severe sepsis cases, in contrast with the ICD-9 code 995.92 for severe sepsis introduced in 2003. They believe that this code may more accurately identify such patients but found it was used only in less than 20% of the cases they evaluated.            

—Beth Tansey Peller, RN

Suggested Reading
Angus DC, Linde-Zwirble WT, Lidicker J, et al. Epidemiology of severe sepsis in the United States: analysis of incidence, outcome, and associated costs of care. Crit Care Med. 2001;29(7):1303-1310.
Angus DC, Wax RS. Epidemiology of sepsis: an update. Crit Care Med. 2001;29(7 Suppl):S109-S116.
Sands KE, Bates DW, Lanken PN, et al. Epidemiology of sepsis syndrome in 8 academic medical centers. JAMA. 1997;278(3):234-240.

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