OVERVIEW
• Systemic inflammatory response syndrome (SIRS) is an exaggerated immune system response to isolate and eliminate any external injurious agent such as infection, malignancy, trauma, surgery, ischemia and acute inflammation
• It is characterized by the release of acute-phase reactants which mediate widespread hematological, autonomic, endocrine and immunological changes in the host
• Although the aim of the response is to protect the host, the dysregulated cytokine storm can result in a massive inflammatory cascade that causes either reversible or sometimes irreversible organ dysfunction and death
• SIRS due to a suspected infection is termed sepsis. Sepsis with failure of one or more organ systems is termed severe sepsis and the occurrence of hemodynamic instability (hypotension) despite intravascular volume repletion is termed septic shock
• Patients at the extremes of age, patients, immunosuppression, and diabetics may present with sepsis and associated complications in the absence of characteristic SIRS criteria

CLINICAL FEATURES OF SIRS
• Fevers, chills or night sweats
• Localized pain or tenderness
• Low blood pressure
• History of trauma (road traffic accident etc)
• Underlying chronic medical condition (COPD, heart disease)

CRITERIA FOR DIAGNOSIS OF SIRS CLINICALLY
• Body temperature more than 38 or less than 36oC
• Heart rate more than 90 beats/minute
• Respiratory rate over 20 breaths/minute or pCO2 less than 32 mmHg (most sensitive indicator of severity)
• White cell count greater than 12000 or less than 4000/cu.mm or more than 10% immature (band forms of neutrophils

COMPLICATIONS OF SIRS
• Respiratory failure
• Pneumonia
• Acute respiratory distress syndrome (ARDS)
• Kidney failure
• Stress ulcers
• Superinfection
• Anemia
• Venous thromboembolism
• Electrolyte disturbances
• Catheter associated bacteremia
• Hyperglycemia
• Disseminated intravascular coagulation (DIC)

WORK UP
Lab tests to consider to rule out other conditions or find the possible etiology include the following
• Blood cultures
• Urinalysis and culture in all patients
• Cardiac enzyme markers
• Sputum culture and Gram stain in patients with respiratory issues
• Amylase
• Lipase
• Cerebrospinal fluid analysis
• Renal profile
• Liver profiles
• Lactate
• Arterial blood gas analysis (to identify acid base disturbances)

ROLE OF INTERLEUKIN-6 (IL-6)
• Persons who demonstrate SIRS along with raised Interleukin-6 (IL-6) levels (>300 pg/mL) are at increased risk for complications such as pneumonia, multiple organ dysfunction syndrome (MODS), and death
• A decrease in IL-6 by the second day of antibiotic treatment is regarded as a positive prognostic sign in patients with an infectious etiology for SIRS

TREATMENT OF SIRS
• Treatment of underlying cause
• Prophylaxis for DVT and stress ulcers
• Intravenous fluids for shock
• Parenteral feeding
• Respiratory support as needed