As the use of SIRS persists, it’s worth re-examining its intended application, potential for error, and current utility.
With the removal of Systemic Inflammatory Response Syndrome (SIRS) criteria from the 2017 Surviving Sepsis Guidelines put forth by the Society of Critical Care Medicine (SCCM) and European Society of Intensive Care Medicine (ESICM), are we beating a dead horse with another discussion about SIRS?1 Given that the Sequential Organ Failure Assessment (SOFA) and Quick SOFA (qSOFA) clinical prediction rules are more recent and effective prognosticators of sepsis mortality, what is the current role of SIRS?2 Despite new guidelines, SIRS continues to be employed ubiquitously throughout emergency departments and medicine floors for a number of reasons. As the use of SIRS persists, it’s worth re-examining its intended application, potential for error, and current utility.
Use and Misuse
SIRS was broadly adopted in 1991 following a consensus conference between the American College of Chest Physicians (ACCP) and SCCM leading to the introduction of SIRS criteria and definitions for sepsis, severe sepsis, septic shock, and MODS (multiple organ dysfunction syndrome).3 Developed as an easy to apply set of parameters that would identify potential candidates for new sepsis treatments, SIRS criteria was built upon a foundation of basic clinical and laboratory data readily available to most clinicians.3 It’s generally agreed upon that the criteria defines a clinical inflammatory response to a non-specific insult (either infectious or non-infectious). The pathophysiology of inflammation occurs independently of the etiology with only minor differences in the inciting cascades, leading to a highly conserved and non-specific process.4 These characteristics explain the high sensitivity and low specificity of SIRS criteria for infection and sepsis. As a tool for identifying sepsis it’s limited by an inability to distinguish a normal physiologic host response from a pathologic host response leading to organ dysfunction.3 Normal physiologic responses to exercise or environment, panic, anxiety, medications and drugs represent common and potentially benign causes of meeting SIRS criteria.
While we academically understand the pathophysiology and intended use of SIRS criteria, in practice there’s a tendency for the reflexive interpretation of infection. When we notice a patient’s vitals or labs meet SIRS criteria, we suffer the potential for sequential cognitive errors. Though speculative, it would seem those at greatest risk for this are medical students and interns, owing to higher levels of fatigue, inexperience, and cognitive load.5 Equating SIRS with infection increases the chances of anchoring, or the tendency to fixate on overarching features of an initial patient presentation without adjusting the impression later despite additional or conflicting information.6 Anchoring routinely leads to confirmation bias in which the clinician seeks out confirmatory evidence for their diagnosis while failing to consider or look for disconfirming data.6A particularly relevant cognitive error to SIRS is the eponymously named Sutton’s slip. This error occurs when diagnoses other than the obvious are not considered or given sufficient consideration.6 These errors lead to a common final pathway resulting in satisfaction of search (cessation of investigation once an abnormality is found) and premature closure (accepting a diagnosis before it has been fully verified).6These mistakes are particularly dangerous in the ED as SIRS can represent the manifestation of various life-threatening emergencies.
Table 1. SIRS Criteria
| Finding (any two of the following | Value |
| Temperature | >38 ˚C (100.4 ˚F) or <36 ˚C (96.8 ˚F) |
| Heart Rate | >90/min |
| Respiratory Rate | >20/min or PaCO2 <32mmHg |
| WBC | >12×109/L (>12,000/mm3) or <4×109/L (<4000/mm3) or 10% bands |
Table 2. SEPTIC Mnemonic for Patients Meeting SIRS Criteria in the ED
| Etiologies | Pearls | |
| Sepsis | Most common infectious sources include skin, lungs, genitourinary tract, abdomen
Bloodstream or foreign objects CNS Unknown |
Look for, inspect, and potentially remove foreign objects (lines, Foley, hardware, etc.)
Immunocompromised patients don’t mount normal inflammatory responses — |
| Endocrine | DKA
HHS Adrenal insufficiency Thyrotoxicosis Myxedema coma Hypo- or hyperglycemia |
Look for an underlying cause in DKA or HHS other than the obvious
Look for cessation of steroids, hypotension, hypoglycemia, low sodium and high potassium in adrenal insufficiency. Death |
| Pancreas | Pancreatitis
|
Ideal time for CT imaging is >48-72 hours from symptom onset |
| Toxins and Trauma | Sympathomimetics
Antipsychotics Anticholinergics |
Avoid beta blockers with cocaine
BDZs for hyperthermia |
| Immune | Systemic Lupus Erythematosus
Rheumatoid arthritis Anaphylaxis |
Chronic inflammatory diseases increase risk of ACS, PE, and pericardial effusion |
| Cardiovascular | Acute Coronary Syndrome
Pulmonary embolism DVT |
Exercise caution giving IVF in massive PE |
Pearls and Avoiding Pitfalls
As masters of the undifferentiated patient, the chief task of an emergency physician is to rule out life- or limb-threatening emergencies. This means considering, but not necessarily testing for all potentially emergent etiologies of a patient’s presentation. While the differential for SIRS is exhaustive and the zebras rare, unlikely sources must always be ruled out. A practical model for thinking about SIRS in the ED is the SEPTIC mnemonic created by Michael Stanley, DO, Program Director of the Transitional Year Residency and practicing EM physician at Kaweah Delta Health Care District in Visalia, California. While not intended to be an exhaustive list, the mnemonic helps to quickly organize your differential for SIRS and ensure potential etiologies aren’t missed. Stopping to think after each patient encounter, asking “Did I miss something?” and quickly using a memory device can be an effective way of minimizing cognitive errors and missed diagnoses in the ED.
References
- Singer M, Deutschman C, Seymour C, et al. Consensus Definitions for Sepsis and Septic Shock. JAMA. 2016;315(8):801-810.
- Raith EP, Udy AA, Bailey M, McGloughlin S, MacIsaac C, Bellomo R, Pilcher DV. Prognostic Accuracy of the SOFA Score, SIRS Criteria, and qSOFA Score for In-Hospital Mortality Among Adults With Suspected Infection Admitted to the Intensive Care Unit. JAMA. 2017;317(3):290–300.
- Balk RA. Systemic inflammatory response syndrome (SIRS): where did it come from and is it still relevant today? Virulence. 2014;5:20–26.
- Systemic Inflammatory Response Syndrome (SIRS). Antimicrobe Website. http://www.antimicrobe.org/e20.asp. Accessed September 22, 2017.
- Hevia A, Hobgood C. Medical error during residency: to tell or not to tell. Ann Emerg Med. 2003;42(4):565-570.
- Croskerry P. The importance of cognitive errors in diagnosis and strategies to minimize them. Acad Med. 2003;78(8):775-780.