What SIRS Stands For
SIRS stands for Systemic Inflammatory Response Syndrome.
Definition and Clinical Criteria
SIRS is defined by the presence of at least two of the following four clinical criteria: temperature >38°C (100.4°F) or <36°C (96.8°F); heart rate >90 beats/min; respiratory rate >20 breaths/min or PaCO₂ <32 mmHg; and white blood cell count >12,000/mm³ or <4,000/mm³ or >10% immature (band) forms. 1, 2, 3
This definition was established by the American College of Critical Care Medicine consensus conference in 1991 to provide an easy-to-apply set of clinical parameters for early identification of patients with systemic inflammation. 4
SIRS can be diagnosed solely based on bedside clinical parameters and basic laboratory values, without requiring pathological specimens or cultures. 2, 3
What SIRS Represents
SIRS is the clinical expression of the acute phase reaction triggered by various events including infection, trauma, surgery, burns, pancreatitis, and other injuries. 1, 2, 5
The syndrome is mediated by cytokines that induce catabolism of glycogen, fat, and protein stores, leading to release of glucose, free fatty acids, and amino acids into circulation to support tissue healing. 1, 2
SIRS represents a common inflammatory response pathway in the host to diverse injuries, providing attractive targets for anti-inflammatory interventions. 4
Key Clinical Distinctions
SIRS differs from sepsis, which requires both confirmation of infection plus SIRS criteria. 2, 3
Septic shock is defined as sepsis with circulatory and cellular/metabolic abnormalities requiring vasopressors to maintain mean arterial pressure ≥65 mmHg and lactate >2 mmol/L. 2, 3
The presence of SIRS should prompt a thorough search for the underlying cause rather than being considered a final diagnosis. 2, 3