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SIRS, Sepsis, and Septic Shock Criteria
Defines the severity of sepsis and septic shock.
February 2016: These criteria are no longer recommended for the diagnosis of sepsis, as they are neither sufficiently sensitive nor specific. For the latest on sepsis, visit our qSOFA Score or the Sepsis-3 Consensus Definitions.
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 ≥ 4 mmol/L is considered the cutoff value for the diagnosis of severe sepsis and the initiation of Early Goal Directed Therapy (EGDT).
Patients who meet the above criteria but are persistently hypotensive despite the initiation of intravenous fluid resuscitation are in Septic Shock and aggressive resuscitation measures should be initiated immediately.
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.
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.
SIRS is commonly used as a screening tool in the emergency department to identify patients at risk for Severe Sepsis. These criteria have not been validated in this setting however.
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.
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. In the emergency department it is a triage tool that helps determine patient acuity and identify patients that are potentially septic and in need of further screening.
Severe Sepsis and Septic Shock are universally accepted as indications to initiate sepsis management protocols such as Early Goal Directed Therapy.
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 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 ≥ 4 mmol/L is considered diagnostic for Severe Sepsis, and aggressive management with broad spectrum antibiotics, intravenous fluids, and vasopressors should be initiated (aka EGDT).
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.
The management of Severe Sepsis and Septic Shock is the topic of intense research and scrutiny.
While Early Goal Directed Therapy has been advocated in the Surviving Sepsis Guidelines, there remains controversy as to which of the bundled interventions are necessary.
Recent studies have showed EGDT not to be better than “usual care”, and called for significant amendments to currently used sepsis protocols.
To date, most experts agree that 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.
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.
Series of Yes/No questions
Facts & Figures
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. Two excellent sepsis references (1, 2) come from the EMCrit website.
This paper was released after the first consensus conference in 1991. The goal of this conference was to standardize the use of terms such as “SIRS”, “sepsis”, “severe sepsis”, and “septic shock” to facilitate enrollment of patients in clinical trials.
In 2001, the International Sepsis Definitions Conference expanded on these definitions by adding additional elements such as laboratory data. See here.
Why did you issue the consensus statement on the SIRS Criteria and Septic protocol? Was there a clinical experience that inspired you to update these guidelines for clinicians?
The American College of Chest Physicians and the Society of Critical Care Medicine convened the first sepsis definitions conference in 1991 to help researchers define a population of severe septic patients who would be suitable for enrollment in clinical trials of new investigational agents that were thought to be able to block the proinflammatory cascade, and thus improve survival of patients with severe sepsis and septic shock. To accomplish this goal, the conference participants aimed to use readily available clinical signs, symptoms and basic laboratory studies that would then support a rapid diagnosis. The trade-off for such a sensitive group of parameters that would alert physicians to the early manifestations of severe sepsis and septic shock was a group of criteria that lacked a great deal of specificity. It was also recognized that the same clinical signs, symptoms and laboratory data seen in patients with severe sepsis and septic shock were also present in other populations of critically ill patients with other proinflammatory conditions, such as trauma, burns, pancreatitis, etc. It was therefore decided to define the patients with a documented or highly suspicious infection that results in a systemic inflammatory response as having sepsis. In the ICU, sepsis patients would typically manifest organ dysfunction (severe sepsis) or septic shock, with or without multiple organ dysfunction syndrome.
The second goal of the consensus conference was to facilitate better communication in the literature and scientific communication (including on rounds) which will enhance future comparative efforts among clinical trials and facilitate outcome comparisons of septic populations.
What pearls, pitfalls and/or tips do you have for users of the SIRS Criteria? Are there cases in which they have been applied, interpreted, or used inappropriately?
Users of the SIRS - Sepsis criteria need to understand that they are overly sensitive to identify potential patients as early as possible, but the criteria lack specificity. The 2001 international sepsis definition conference attempted to enhance the utility and specificity of the definition by including additional signs, symptoms, laboratory data, biomarkers and physiologic parameters. Unfortunately, we are still awaiting the perfect clinical definition that has both high sensitivity and specificity for severe sepsis and septic shock.
For example, if you believe the patient has an infection AND meets the SIRS criteria, then the patient may be septic. Infection is likely its most useful application. The score is designed to be sensitive, but not specific. It's meant to help with early diagnosis. SIRS was not designed to be algorithmic, such as: if you have a score of X, you must do Y. Rather, it's a table of points to see whether or not the patient has any of these criteria. You then apply that result to the specific clinical scenario.
What recommendations do you have for health care providers once they have applied the SIRS Criteria? Are there any adjustments or updates you would make to the criteria given recent changes in medicine?
Investigators are continuing to refine the SIRS - Sepsis criteria and make them more clinically useful. The current approach has involved the use of various biomarkers to facilitate the identification of patients with a high likelihood of bacterial infection and/or high risk for morbidity and mortality. Some of the current biomarkers under evaluation include procalcitonin, C-reactive protein, proadrenalmodulin, N-terminal BNP and lactate.
Other comments? Any new research or papers on this topic in the pipeline?
The future will likely include significant refinements in the SIRS criteria using biomarkers and PCR or nanotechnology to improve the specificity of the diagnosis and provide the information in a more rapid fashion.
About the Creator
Robert A. Balk, MD, is a professor and practicing physician in pulmonology, internal medicine and critical care at Rush University Medical Center. His research interests include septic shock, acute lung injury, acute respiratory distress syndrome and ventilator-associated pneumonia.
To view Dr. Robert A. Balk's publications, visit PubMed