Systemic inflammatory response syndrome as a clinical detection tool and inclusion criterion in sepsis trials: too blunt an instrument?
© BioMed Central Ltd 2008
Published: 13 March 2008
The term systemic inflammatory response syndrome (SIRS) was introduced in 1992  and has frequently served as a criterion for enrollment in sepsis trials. In the present study, the prevalence of SIRS in patients with significant bacterial infections and in patients with septic shock was assessed.
A cohort of 404 adult patients admitted to the Department of Infectious Diseases from the emergency room (ER) for suspected severe infection was studied prospectively. Of the SIRS variables, white blood cells (WBC) were measured on arrival while the physiological variables (temperature, heart rate (HR) and respiratory rate (RR)) were recorded on arrival to the ER and every 4 hours for 24 hours. In another cohort of 36 consecutive adults with vasopressor-dependent septic shock, the presence of SIRS criteria during 24 hours around the start of vasopressors was evaluated.
Bacterial infections requiring antibiotic treatment were diagnosed in 306 patients in the ER cohort. Nonbacterial infection or noninfection was diagnosed in 82 patients. In 16 patients, no diagnosis could be verified. Significant bacteremia was detected in 68 patients; the most common pathogens were pneumococci and Escherichia coli. Of the 306 patients with a verified bacterial infection and of the 68 with verified bacteremia, 26% and 21%, respectively, failed to meet two or more of the SIRS criteria on arrival in the ER. SIRS on arrival correlated significantly with bacterial infection, but not with bacteremia. Only RR and WBC contributed significantly to this finding, HR and temperature did not. In the septic shock group, all patients eventually fulfilled the HR and RR criteria but only 23/36 (64%) reached the temperature criterion and 25/36 (69%) the WBC criterion during 24 hours.
SIRS correlated with a subsequently verified bacterial infection requiring antibiotic treatment, but only the RR and WBC criteria contributed to this finding. As a tool for defining sepsis and selecting patients for enrollment in clinical sepsis trials, SIRS is nonspecific, and for ≥ 3 fulfilled criteria it lacks sensitivity. It may be time to abandon the SIRS criteria in selecting patients for sepsis trials and instead focus on more strict definitions of underlying infections in association with sepsis-related hypoperfusion and organ dysfunction.