From the Guidelines
The Systemic Inflammatory Response Syndrome (SIRS) criteria are defined by the presence of two or more of the following: body temperature >38°C or <36°C, heart rate >90 beats per minute, respiratory rate >20 breaths per minute or PaCO2 <32 mmHg, and white blood cell count >12,000/mm³, <4,000/mm³, or >10% immature bands, as described in the most recent and highest quality study 1.
Definition of SIRS Criteria
The SIRS criteria are a set of clinical parameters used to identify patients with potential systemic inflammation that may indicate sepsis. These criteria include:
- Body temperature >38°C (100.4°F) or <36°C (96.8°F)
- Heart rate >90 beats per minute
- Respiratory rate >20 breaths per minute or PaCO2 <32 mmHg
- White blood cell count >12,000/mm³, <4,000/mm³, or >10% immature bands These criteria help clinicians rapidly identify patients who may be developing a serious inflammatory response, which could be due to infection (sepsis) or other causes like trauma, burns, or pancreatitis.
Importance of SIRS Criteria
While SIRS criteria are sensitive for detecting systemic inflammation, they lack specificity for sepsis specifically. Therefore, when SIRS criteria are met, clinicians should perform a thorough evaluation to determine the underlying cause and initiate appropriate management. Early recognition using these criteria is crucial as prompt intervention, particularly with antibiotics in cases of sepsis, significantly improves patient outcomes by preventing progression to severe sepsis or septic shock, as supported by studies such as 1 and 1.
Clinical Application
In clinical practice, the SIRS criteria are used in conjunction with other diagnostic tools to identify patients at risk of sepsis. For example, the Infectious Diseases Society of America (IDSA) classification system for diabetic foot infections uses the SIRS criteria to define the severity of infection 1. Newer scoring systems like qSOFA (quick Sequential Organ Failure Assessment) are now often preferred for sepsis screening in many clinical settings, but the SIRS criteria remain an important tool for identifying patients with potential systemic inflammation.
From the Research
SIRS Criteria Definition
- The Systemic Inflammatory Response Syndrome (SIRS) criteria are used to assess and diagnose patients with infection, organ failure, and inflammatory responses 2.
- SIRS criteria include parameters such as respiratory rate, heart rate, leukocyte count, and temperature 2, 3.
Association with Mortality
- Different individual and combinations of SIRS criteria are associated with marked differences in hospital mortality, ranging from 10.6% to 30.8% depending on the combination of criteria 2.
- Mortality increases with certain SIRS criteria, such as heart rate and low leukocyte count, and decreases with others, such as high temperature 2.
Relationship with Vancomycin Dose Requirement
- Patients with SIRS have a significantly higher vancomycin clearance than those without SIRS, indicating a higher elimination capacity 3.
- Vancomycin clearance is positively correlated with the SIRS score, defined as the number of positive items in the criteria, and negatively with age, except in patients with renal dysfunction 3.
Molecular Pathophysiology
- SIRS can be precipitated by non-infective events such as trauma, pancreatitis, and surgery, and is characterized by an overactive inflammatory response 4.
- Production and activation of multiple proinflammatory genes play a key role in the pathogenesis of multiple organ dysfunction syndrome (MODS) development 4.