Systemic inflammatory response syndrome and severe sepsis definitions outside the intensive care unit: contribution or confusion?

Background

The terms systemic inflammatory response syndrome (SIRS), sepsis, severe sepsis and septic shock were defined in 1992 and have been universally accepted. In the present study, the prevalence of SIRS and severe sepsis in patients with significant bacterial infections was assessed.

Methods

A total of 404 adult patients admitted to the Department of Infectious Diseases from the emergency room (ER) for suspected severe infection was studied prospectively. Laboratory variables defining SIRS and severe sepsis were measured on arrival while physiological variables were recorded on arrival in the ER and every 4 hours for 24 hours.

Results

Bacterial infections requiring antibiotic treatment were diagnosed in 306 patients. One hundred and fifty of these developed severe sepsis during the first 24 hours. Significant bacteremia was detected in 68 patients. In these three groups 26%, 22% and 21%, respectively, failed to meet two or more of the SIRS criteria on arrival in the ER. In the group of patients that did not have an infection nor did not need antibiotic treatment, 63% had SIRS on arrival. SIRS on arrival correlated significantly with bacterial infection and development of severe sepsis, but not with bacteremia. Of the SIRS criteria, only the respiratory rate and white blood count contributed significantly to this finding; the heart rate and temperature did not. Intensive care was required for 14/150 patients (9%) with severe sepsis and for 6/68 (9%) bacteremic patients. Altogether 11/404 (2.7%) patients died within 28 days.

Conclusion

As a tool for definition of sepsis and selection of patients for clinical sepsis trials, SIRS lacks acceptable sensitivity and specificity in a selected ER population with a high risk of serious infection. Excluding patients with less than two or even three SIRS criteria may exclude a large cohort of patients with sepsis and result in biased enrollment to clinical trials. It may be time to abandon the SIRS criteria as an entry criterion for sepsis trials and to instead focus on more strict definitions of underlying infections in association with sepsis-related hypoperfusion and organ dysfunction. Many of the patients developed severe sepsis within 24 hours, yet only a small proportion required intensive care, putting the term severe sepsis into question. Severe sepsis in the ICU setting is known to be associated with a high mortality, whereas this might not be the case outside the ICU.