The Third International Consensus Definitions for Sepsis and Septic Shock

sepsis and septic shock

Sepsis is the most common pathway to death following an infection…and it can be avoided! How? With early recognition and timely intervention! Earlier this year, the Sepsis Definitions Task Force members released the Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). But in order to appreciate the need for a new definition, we must first understand the issues with the old definition. 

  • Sepsis: known or suspected infection + 2 or more Systemic Inflammatory Response Syndrome (SIRS) criteria
    • Temperature more than 38 °C or less than 36 °C
    • Heart rate more than 90 beats per minute
    • Respiratory rate more than 20 breaths per minute or PaCo2 less than 32 mm Hg
    • White blood cell count more than 12,000 mcL or less than 4,000 mcL, or more than 10% immature bands
  • Severe sepsis: sepsis with organ dysfunction, hypoperfusion or hypotension
  • Septic shock: sepsis with hypotension and perfusion abnormalities despite adequate volume resuscitation


So why the need for a change in definition? Let’s start with a little english tutorial! What is the definition of a definition? Simply put, a definition is a statement that describes what something is. The biggest issue with the old definition is that it does not describe what sepsis actually is, it merely gives us a simplistic set of criteria that must be met in order to diagnose a patient with sepsis. And now that we have a better understanding of the pathophysiology of sepsis, we know that SIRS is actually an appropriate response to infection. It is when this response is dysregulated that the problems start. Therefore, sepsis is so much more than an infection plus 2 or more SIRS criteria. So what is the new definition of sepsis?

Sepsis: a life threatening organ dysfunction caused by a dysregulated host response to infection

This new definition  emphasises the importance of the non-homeostatic host response to infection, the potential lethality that is considerably in excess of a straightforward infection, and the need for urgent recognition. Simply put, it takes away an airy fairy “definition” of sepsis and replaces it with a definition that instils a sense of urgency in our response to the condition. This sense of urgency is warranted as sepsis should generally elicit greater levels of monitoring and intervention, as even a modest degree of organ dysfunction when an infection is first suspected is associated with an in-hospital mortality in excess of 10 percent! If a patient has sepsis, we should immediately consider it as a severe condition which therefore makes the old definition of severe sepsis redundant! 

So instead of looking for SIRS criteria in order to diagnose sepsis, we now look for an infection that has resulted in an increase in the Sequential [Sepsis-related] Organ Failure Assessment (SOFA) score of 2 points or more:


The rationale for an increase in the SOFA score by 2 or more from baseline is to allow for patients having pre-existing comorbidities that already result in a SOFA score of 2 or more. If the patient is previously healthy, assume a SOFA score of 0. An increasing SOFA score indicates worsening multiple organ dysfunction and is therefore associated with an increased mortality. Where a SOFA score of 2 is associated with a 10 percent mortality rate, a SOFA score of 15 or more is associated with a 90 percent mortality rate.


In critical care areas where frequent blood samples are drawn, the SOFA score can be easily calculated. However, this may not be as easy outside the critical care areas. But worry not; rigorous analysis has identified that any 2 of the following 3 clinical variables offer a predictive validity similar to that of the full SOFA score outside of critical care areas:

  • Glascow Coma Scale (GCS) less than 15
  • Systolic blood pressure of 100 mmHg or less
  • Respiratory rate 22 breaths per minute or greater

These 3 clinical variables are known as the quick SOFA (qSOFA) score and can be easily performed on every patient. A patient with a qSOFA score of 2 or more should prompt clinicians to further investigate for organ dysfunction with a full SOFA score, initiate or escalate therapy as appropriate, consider referral to critical care or increase the frequency of monitoring and consider the possibility of infection in patients not previously recognised as infected. 


Now let’s consider the definition of septic shock. The definition of shock is a life threatening medical condition of low blood perfusion to tissues resulting in cellular injury and inadequate tissue function. Therefore, it makes sense that septic shock is the above definition secondary to an infective source. However, the definition of shock sounds extremely similar to the definition of sepsis. So then the question becomes, what differentiates sepsis from septic shock? MORTALITY! In simple terms, septic shock is “really bad” sepsis!

Septic shock: subset of sepsis in which particularly profound circulatory, cellular and metabolic abnormalities are associated with a greater risk of mortality than with sepsis alone

Septic shock is clinically identified by vasopressor requirement to maintain a mean arterial pressure (MAP) of more than 65 mmHg AND serum lactate level greater than 2 mmol/L in the absence of hypovolemia

As the clinical identification of septic shock is based on the absence of hypovolemia, intravascular fluid replacement is the initial management choice for hypotension in a patient with sepsis. It is not uncommon for a patient to require approximately 2 – 3 litres of intravascular fluid replacement in the first 6 hours of a septic presentation. There are two pathways that follow this initial management strategy:

  • Adequate perfusion: patients respond to the intravenous fluid replacement with an improved blood pressure and perfusion —> reduce the rate of fluid administration while continuing to monitor clinical and laboratory parameters closely
  • Inadequate perfusion: despite aggressive intravenous fluid replacement, the patient still demonstrates persistent hypotension and hypoperfusion demonstrated by an increased serum lactate level —> vasopressor therapy required to improve perfusion

In terms of overall management of a patient presenting with sepsis, the surviving sepsis campaign advocates the following bundles of care:

  • To be completed within 3 hours of time of presentation
    • Measure lactate level
    • Obtain blood cultures prior to administration of antibiotics (although antibiotics should not be significantly delayed in order to obtain blood cultures)
    • Administer broad spectrum antibiotics
    • Administer 30 mL/kg crystalloid fluid for hypotension or lactate more than 4 mmol/L
  • To be completed within 6 hours of time of presentation
    • Apply vasopressors to maintain a MAP greater than 65 mmHg (for hypotension that does not respond to initial fluid resuscitation)
    • In the event of persistent hypotension after initial fluid administration or if initial lactate was more than 4 mmol/L:
      • Re-assess volume status and tissue perfusion with either:
        • A repeat focused exam by a licensed independent practitioner including vital signs, cardiopulmonary, capillary refill, pulse and skin findings
      • Or two of the following:
        • Measure central venous pressure (CVP)
        • Measure central venous oxygen saturations (ScvO2)
        • Beside cardiovascular ultrasound
        • Dynamic assessment of fluid responsiveness with passive leg raise or fluid challenge
    • Remeasure lactate, if initial lactate was elevated

So what are the little changes that we can implement to our practice to ensure that we are doing our part to recognise sepsis and septic shock early at the bedside? We can start doing a mini-mental qSOFA score on all our patients as part of our daily assessment; alerting others to the potential need to assess for organ dysfunction if the patient scores 2 or more. From there, the following flowchart demonstrates the diagnostic pathway for sepsis and septic shock:


The earlier we pick up sepsis and intervene according to the Surviving Sepsis Campaign Bundles of Care, the better the outcome for our patients! When it comes to sepsis, early recognition and timely intervention SAVES LIVES!


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5 thoughts on “The Third International Consensus Definitions for Sepsis and Septic Shock

  1. Thanks for a great article Jo. It has really helped me to get a better grasp of what sepsis is about.
    Looking forward to reading more of your work


  2. I host a blog
    And a Facebook page #ECT4Health
    I do my best to write informative and entertaining posts, but after reading this write up on sepsis, I know realise that I am a tiny bloke playing among giants.
    Your post was exceptional and I’m going to link it to share. If you can teach face to face , like you write, you should contact me via the page and you have that opportunity.
    Sensational . Thank you

    Liked by 1 person

    • Hi Rob,

      Wow! Thank you for such lovely feedback! It means a lot coming from someone like you who has such an online presence in the world of nursing education! When I read blogs and scan associated social media accounts from clinicians such as yourself, I know I have a LOOOOONG way to go in building even half the readership that others have and becoming a household name in the world of nursing education! In the mean time, I’m really enjoying populating this blog with articles that people are finding interesting and informative 🙂



    • Hi Rick,

      I’m glad that this has helped clear up some of the definitions out there, as well as the management priorities. I think the early recognition and timely management of sepsis is something that all of us clinicians have much room to improve! And these new definitions place the emphasis on the importance of early recognition and management, by making clinicans realise that it is not just “septic shock” that is bad…plain ol’ “sepsis” is also pretty bad!



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