Systemic inflammatory response syndrome (SIRS) is an exaggerated defense response of the body to a noxious stressor (infection, trauma, surgery, acute inflammation, ischemia or reperfusion, or malignancy to name a few) to localize and then eliminate the endogenous or exogenous source of the insult.¹
When working up someone for sepsis or a suspected sepsis, for instance, consider the following:
I. Clinical infection or definitive evidence (culture) of bacteraemia; may be low-grade or transient
II. Systemic Inflammatory Response Syndrome (SIRS)
- core body temperature ≥ 38°C (or ≤ 36°C)
- HR ≥ 90
- RR ≥ 20
- respiratory alkalosis
- WCC ≥ 12 x 10^9/L (PaCO2 ≤ 32 mmHg)
- immature neutrophil “bands” > 10%
III. Multiorgan Dysfunction Syndrome (MODS) – a person meeting any of the following criteria for 1 hour
- CVS: arterial SBP ≤ 90 mmHg (MAP ≤ 70)
- Renal: Urine Output < 0.5 mL/kg per hour
- Resp: PaO2 ≤ 75 mmHg (room air)
- Haem: Platelet count < 80 x 10^ 9/L (or 50% of max. last 3 days)
- CNS: somnolence, confusion, agitation, delirium, coma
Level 1 + two Level 2 criteria = sepsis
Corresponding mortality rates:
Level 2 Criteria:
- 2 criteria: 7%
- 3 criteria: 10%
- 4 criteria: 17%
I + ≥ 2 x II + ≥ 1 x III = severe sepsis:
- + 15-20% mortality per afflicted organ
I + ≥ 2 x II + refractory III = septic shock:
- > 50-80% mortality
It behooves the clinician to treat all infection as a matter of urgency, and all serious infection as an emergency. Because of a relatively short bacterial doubling time, as little as 20 minutes for common pathogens like E. coli, it takes very little time for an infection to become serious and a serious infection to become life-threatening.
References
Chakraborty RK, Burns B. Systemic Inflammatory Response Syndrome. [Updated 2020 Nov 16]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK547669/.