SIRS, Sepsis, and Septic Shock Criteria

Why Use

Early initiation of broad spectrum antibiotics and aggressive resuscitative measures have been shown to decrease mortality in patients with severe sepsis and septic shock. The early recognition of these conditions is therefore of the utmost importance. SIRS criteria are mostly used as a screening tool to identify patients that may need further workup for sepsis and severe sepsis. Severe sepsis and septic shock are universally accepted as indications to initiate sepsis management protocols. Having clearly defined criteria for SIRS, sepsis, severe sepsis, and septic shock is also important in order to standardize clinical research, as well as institutional protocols for the management of these conditions.

When to Use

Patients that present with two or more SIRS criteria and a suspected or confirmed infection should be screened for Severe Sepsis. Currently many institutions encourage or even mandate obtaining a lactic acid level on these patients. A lactate ≥2 mmol/L is considered elevated and the initiation of standard sepsis care is warranted if the patient meets other diagnostic criteria for sepsis. Patients who meet the above criteria but are persistently hypotensive despite the initiation of intravenous fluid resuscitation are likely to be in septic shock and aggressive resuscitation measures should be initiated immediately.

Formula

Pearls / Pitfalls

SIRS, sepsis, severe sepsis, and septic shock criteria were chosen by a panel of experts and not prospectively or retrospectively derived from large-scale population studies ( SCCM 2021 Guidelines ). There remains controversy over the sensitivity and specificity of these criteria, even though they have been largely adopted for the purpose of research and in clinical practice. Clinical judgment remains important since a significant number of patients presenting to emergency departments will meet criteria for sepsis but do not require further screening or management. For example, a 21 year old healthy male with a viral illness can present with a fever and tachycardia. While this patient meets the definition of sepsis, one can easily argue further investigation and aggressive interventions are likely unnecessary if the patient is well appearing.

Management

When a patient presents with two or more SIRS criteria but with hemodynamic stability (i.e. blood pressure at baseline), a clinical assessment must be made to determine the possibility of an infectious etiology. If an infection is suspected or confirmed, the patient is diagnosed with sepsis and a lactate level is obtained to determine the degree of hypoperfusion and inflammation. A lactate level ≥2 mmol/L is considered elevated , and aggressive management with broad spectrum antibiotics, intravenous fluids, and vasopressors should be considered. Patients that present with a suspected or confirmed infection AND hemodynamic instability should immediately be treated for septic shock. While SIRS criteria will likely be present in these patients, aggressive management should not be delayed while waiting for laboratory values such as the WBC or lactate. Early recognition of sepsis, severe sepsis, and septic shock, and early administration of broad spectrum and organism specific antibiotic are the most critical actions. There remains controversy in the type of fluids that should be used, their quantity, and the timing of vasopressors and/or inotropes.

Critical Actions

Assess all patients presenting with two or more SIRS criteria for the possibility of an infectious etiology. Screen for severe sepsis by obtaining a lactate level on patients with sepsis that are elderly, immunocompromised, or ill appearing. Some experts recommend obtaining a lactate level on all patients in whom blood cultures are sent. This is institution dependent however and not mandated in any guidelines. When severe sepsis or septic shock are identified, initiate broad spectrum antibiotics immediately. These antibiotics should be organism specific and therefore institutional antibiograms should be used. The Surviving Sepsis Campaign Guidelines recommend initiation of antimicrobials within one hour from the time of recognition of severe sepsis or septic shock, or within three hours of the patient’s arrival to the hospital.

More Information

SIRS - 2 YES answers meets criteria. Sepsis Criteria - 2 YES of SIRS + Suspected Source of Infection. Severe Sepsis Criteria - 2 YES of SIRS + Lactic Acidosis, SBP. Multiple Organ Dysfunction Syndrome - 2 YES of SIRS + Evidence of ≥ 2 Organs Failing. Check with your own hospital for its sepsis guidelines, sepsis 'bundle', or sepsis algorithm.