“The third international consensus definitions for sepsis and septic shock (sepsis-3),” JAMA 315: 801, 2016, SCCM sepsis definitions task force
Intro:
- initial definitions of sepsis, severe sepsis, and septic shock from 1991; defined severe sepsis as sepsis complicated by organ dysfx which could progress to septic shock, defined as hypotension despite adequate fluid resuscitation; revisited in 2001
- the definitions of sepsis, severe sepsis, and septic shock have remained largely unchanged for more than 2 decades
Process of developing new definitions:
- recognizing the need to reexamine current definitions, the euro society of critical care medicine and the society of critical care medicine convened a task force (TF) of 19 experts in critical care, ID, surgery, and pulmonology (no EM) in jan 2014
- existing definitions were revisited in light of an enhanced appreciation of the pathobiology and the availability of large EMR databases and pt cohorts
- expert consensus process forged agreement on updated definitions and the criteria to be tested in the clinical arena
- the agreement between potential clinical criteria and the ability of the criteria to predict outcomes (eg ICU admission, mortality) were then tested in multiple large EMR databases
- systematic lit review/metaanalysis and delphi consensus methods were also used for the definition and clinical criteria describing septic shock
- when compiled, the TF recommendations were circulated to major international societies and other relevant bodies for peer review and endorsing (a total of 31 endorsing societies) (again, no EM)
Challenges and opportunities:
- because no gold standard diagnostic tests exist for sepsis, the TF sought definitions and supporting clinical criteria that were clear and fulfilled multiple domains of usefulness and validity
- the original conceptualization of sepsis as infection + ³2 SIRS criteria focused solely on inflammatory excess; sepsis is now recognized to involve early activation of both pro- and anti-inflammatory responses, along with major modifications in nonimmunologic pathways such as cardiovascular, neuronal, autonomic, hormonal, bioenergetic, metabolic, and coagulation, all of which have prognostic significance; a broader perspective also emphasizes the significant biological and clinical heterogeneity in affected individuals
- the current ³2 SIRS criteria to identify sepsis was unanimously considered by the TF to be unhelpful
- the “sequential organ failure assessment” (SOFA) score looks at severity of organ dysfx via the following variables: P/F ratio (resp), platelets (coag), bili (liver), BP (cardiovascular), GCS (neuro), creat and UO (renal); a higher SOFA score is associated with increased mortality, but outside the critical care community the score is not well known + cumbersome to use
- multiple definitions for septic shock are currently in use resulting in significant heterogeneity in reported mortality
- the public needs an understandable definition of sepsis and health care providers require improved clinical prompts and diagnostic approaches to facilitate earlier identification and an accurate quantification of the burden of sepsis
Results/recommendations:
Definition of sepsis:
- sepsis is defined as life-threatening organ dysfx caused by a dysregulated host response to infection
- under this definition (“life-threatening organ dysfx”), the term “severe sepsis” becomes superfluous
Clinical criteria to identify pts with sepsis:
- the TF evaluated which clinical criteria best identified pts most likely to have sepsis; this objective was achieved by interrogating large datasets of hospitalized pts with presumed infection, assessing agreement among existing scores of inflammation (SIRS) or organ dysfx (SOFA), and delineating their correlation with subsequent outcomes; in addition, multivariable regression was used to explore the performance of 21 bedside and lab criteria proposed by the 2001 TF
- the EMR included 150,000 pts with suspected infection (from 12 hosps within the univ of pittsburgh system); two outcomes – ICU stay ³3 days and mortality – were used to assess predictive validity
- for ICU pts, a change in SOFA score ³2 from baseline was superior to SIRS criteria; the TF recommends the use of SOFA score ³2 from baseline to identify life-threatening organ dysfx and, thus, sepsis
- for non-ICU pts, the TF found that 2 or more of the following clinical variables – altered mental status, syst BP £100, and RR ³22 – offered good predictive validity; this new measure is termed qSOFA (for quick SOFA) and provides simple bedside criteria to identify life-threatening organ dysfx and, thus, sepsis; the TF recommends that qSOFA criteria be used to prompt clinicians to further investigate organ dysfx, to initiate or escalate therapy as appropriate, and to consider referral to critical care specialists
- thus, for ER pts, the TF recommends the following for identification of pts with sepsis: ³2 of the qSOFA criteria: altered MS, syst BP £100, RR ³22
Definition of septic shock:
- septic shock is a subset of sepsis in which underlying circulatory and cellular metabolic abnormalities are profound enough to substantially increase mortality
Clinical criteria to identify septic shock:
- 3 variables were identified to test in cohort studies – MAP <65, lactate >2, and need for vasopressor(s) to maintain MAP ³65 after volume resuscitation
- the first database interrogated was the surviving sepsis campaign’s international multicenter registry; a total of 20,000 septic pts; the mortality for septic pts with all 3 variables was >40%
- these same 3 variables were then used to interrogate 2 unrelated large EMR datasets – univ of pittsburgh (12 hosps, 6,000 pts) and kaiser (20 hosps, 54,000 pts); the mortality for septic pts with all 3 variables was 35-55%
- thus, the TF recommends the following criteria for identification of pts with septic shock: MAP <65, lactate >2, and need for vasopressor(s) to maintain MAP ³65 after volume resuscitation
Controversies – lactate levels:
- because lactate offered no meaningful change in the predictive validity beyond ³2 of the qSOFA criteria in the identification of pts with sepsis, the TF could not justify adding the complexity/cost of lactates alongside these simple bedside criteria
- the TF recommendations should not, however, constrain the monitoring of lactate as an indicator of illness severity or as a guide to therapeutic response
- some TF members suggested that elevated lactate represents an important marker of “covert shock” in the absence of hypotension
Implications:
- simple clinical criteria (qSOFA) that identify pts with sepsis (ie pts with evidence of infection who are likely to have a prolonged ICU course +/- death) have been developed and validated
- there is potential conflict with current organ dysfx scoring systems, early warning scores, ongoing research studies, and pathway developments
“Editorial: new definitions for sepsis and septic shock: continuing evolution but with much still to be done,” wake forest
- the TF assessed the predictive validity of SOFA, SIRS, and qSOFA in a primary cohort that included 150,000 pts with suspected sepsis and a confirmatory analysis that included 700,000 pt encounters at 156 US and non-US hosps
- for identifying pts with sepsis: the investigators found that in the ICU the best predictive value was found with change in SOFA score >2 from baseline; in non-ICU settings, the best predictive value was found with the qSOFA score
- for identifying pts with septic shock: the TF conducted a systematic review and metaanalysis of 92 studies informing a delphi process that created the new definition, then tested the variables identified by the delphi process in cohort studies using datasets from the surviving sepsis registry, univ of pittsburgh hosps, and kaiser hosps
- according to the new recommendations:
- sepsis is now identified by evidence of infection + life-threatening organ dysfx, clinically characterized by an acute change in the SOFA score ³2 from baseline (ICU pts) or ³2 of the 3 clinical variables of the qSOFA score (nonICU pts)
- septic shock is now identified by MAP <65, lactate >2, and the need for vasopressor(s) to maintain MAP >65 after volume resuscitation
- there is no longer any mention of the SIRS criteria (HR >90, RR >20, T >38° or <36°, WBC >12K or bands >10%)
- there remain concerns with the quality of the information used to generate the updated criteria
- regarding the new qSOFA score: because this score was retrospectively derived from databases that had substantial gaps in clinical info for pts treated outside ICUs, qSOFA will require prospective real-world validation before it should enter routine clinical practice