Sepsis - definition and clinical framing
Definition (UK)
- NICE frames sepsis as “a clinical syndrome caused by the body's immune and coagulation systems being switched on by the presence of infection (bacteria or viruses) in the blood” (NICE NG51).
- NICE describes “sepsis with shock” as life‑threatening low blood pressure despite adequate fluid replacement, with associated organ dysfunction or failure (NICE NG51).
International definition (Sepsis‑3) - contrast
- Sepsis‑3 (2016) defines sepsis as “life‑threatening organ dysfunction caused by a dysregulated host response to infection” and operationalises this as an acute change in SOFA score ≥ 2.
- Septic shock (Sepsis‑3) is defined as persisting hypotension requiring vasopressors to maintain MAP ≥ 65 mmHg and a serum lactate
> 2 mmol/L despite adequate volume resuscitation.
- UK guidance recognises the conceptual value of Sepsis‑3 but places primacy on early clinical recognition and escalation using early‑warning systems (for adults, NEWS2) rather than routine use of SOFA for initial screening (NICE NG51; RCEM).
Why definitions matter in practice
- Sepsis‑1/2 (SIRS‑based) prioritised sensitivity but lacked specificity - many infected patients meet SIRS without life‑threatening organ dysfunction.
- Sepsis‑3 improved specificity by centring on organ dysfunction (SOFA) and prognosis, but relying solely on organ‑dysfunction thresholds risks delayed recognition of evolving sepsis.