Felis ISSN 2398-2950

Systemic inflammatory response syndrome (SIRS)

Contributor(s): John Dodam, Philip K Nicholls


  • SIRS is a condition associated with activation of multiple inflammatory pathways that often results in severe organ dysfunction and death.
  • The malignant inflammatory cascade can be triggered by a multitude of specific conditions including trauma, thermal tissue damage, infectious disease, toxins or inflammation.
  • Progression of SIRS results in multiple organ dysfunction Multiple organ dysfunction syndrome (MODS), and can cause death. Indeed, multiple organ dysfunction is an important cause of death in human ICU patients and may have a mortality rate of 40-90%. Mortality is probably similar in veterinary patients.
  • Extensive research is ongoing to delineate the pathophysiology of SIRS. Identification of the molecular and cellular triggers that give rise to organ system dysfunction may lead to specific and effective therapy for the syndrome.
  • The exact incidence of SIRS is not known in the veterinary patient population.
  • Sepsis Shock: septic and bacteremia is probably the most common cause of SIRS in veterinary patients.
  • Pyothorax Pyothorax, septic peritonitis Peritonitis, gastroenteritis, pneumonia Pneumonia  , endocarditis Endocarditis, pyelonephritis Pyelonephritis, osteomyelitis, pyometraPyometra and bite wounds are all conditions that can lead to sepsis in feline patients.
  • In addition, the use of invasive monitoring, diagnostic and therapeutic procedures may increase risk of infection. Because veterinarians are becoming more sophisticated and are using invasive diagnostic and therapeutic techniques more frequently, it is reasonable to assume that the incidence of SIRS and sepsis will increase in the hospitalized patient population.



  • SIRS is caused by activation of a systemic inflammatory response that involves the biosynthesis of cytokines, lipid mediators of inflammation, and reactive oxygen molecules.
  • Initiation of the coagulation cascade and the production of acute phase reactants may also play a role in the development of SIRS.

Predisposing factors


  • Trauma.
  • Infection.
    • Viral.
    • Fungal.
    • Bacterial-bacterial sepsis is probably the most important cause of SIRS in veterinary patients.
  • Thermal tissue damage (burns).
  • Toxins.
  • Inflammatory diseases.
  • Surgery.
  • Catheterization.


  • SIRS is secondary to a variety of insults that result in a systemic inflammatory response.
  • SIRS is the result of a variety of systemic inflammatory pathways.
  • The dramatic and generalized nature of the response is what results in dysfunction.
  • It is speculated that each component of the response is designed to be protective when the response is local in nature.
  • The production of cytokines (tumor necrosis factor, interleukins 1 and 6 and interferons), lipid mediators of inflammation (platelet activating factor, prostaglandins, leukotrienes), and activation of the coagulation cascade, coupled with the activation of endothelial cells and numerous immune cells results in multiple organ dysfunction and altered immune response.
  • Sepsis is commonly associated with SIRS in veterinary species.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Cassutto B H & Gfeller R W (2003) Use of intravenous lidocaine to prevent reperfusion injury and subsequent multiple organ dysfunction syndrome. J Vet Emerg Crit Care 13 (3), 137-48 VetMedResource.
  • Brady C A, Otto C M, Van Winkle T J et al (2000) Severe sepsis in cats: 29 cases (1986-1998). J Am Vet Med Assoc 217 (4), 531-535 PubMed.

Other sources of information

  • Kirby R (1995) Septic shock. In: Current Veterinary Therapy XII. Eds J D Bonagura and R W Kirk. Philadelphia: W B Saunders. pp 139-146.