What is sepsis and why is it so dangerous?

Sepsis is life-threatening organ dysfunction due to a dysregulated host response to infection (Sepsis-3 definition).

There are 150,000 cases every year in the UK resulting in 44,000 deaths – more than bowel, breast and prostate cancer combined.

What is sepsis?

Clinical criteria for diagnosing sepsis were first proposed in 1991 and then updated in 2001. The latest definition was reached by a task force of critical care experts and is known as the Sepsis-3 definition.

A more simple definition proposed by the Sepsis Alliance is – Sepsis is the body’s overwhelming and life-threatening response to infection which can lead to tissue damage, organ failure, and death.

The infection

Sepsis is always triggered by an infection whether or not that infection can be diagnosed. Pneumonia, urinary infections, cellulitis, infected wounds, dental abscesses and appendicitis are common causes of sepsis. Bacteria are the usual culprits, but viruses, fungi and parasites can all trigger sepsis.

The body’s normal response to an infection.

With any infection the body’s immune system goes into action. Vasodilation releases white blood cells to the site of the infection and platelets form clots in the tissues to seal the area off.


In sepsis this response, typically seen only around the infection site, spreads through the body, affecting healthy tissue and organs. Vasodilation occurs throughout the body causing hypotension and potential organ dysfunction. The release of platelets form clots in capillaries leading to possible tissue necrosis. Sepsis can affect anyone but usually it is the most vulnerable, such as babies, young children and the elderly, as well as anyone with a weakened immune system.

Why is it so dangerous?

Sepsis progresses rapidly and needs to be treated quickly to prevent tissue damage, organ failure, and death. It needs to be responded to in the same way as we respond to a suspected myocardia infarct (MI) or cerebral vascular accident (CVA) There are 150,000 cases of sepsis every year in the UK resulting in 44,000 deaths – more than bowel, breast and prostate cancer combined. Many of these could be prevented if action had been taken sooner.

The Sepsis-3 task force identified 3 criteria that can used to diagnose suspected sepsis outside of an intensive care setting:

  • Respiratory rate ≥ 22
  • Altered level of consciousness
  • Systolic blood pressure ≤ 100mmHG

If 2 or more are present together with an infection the patient needs immediate emergency treatment so that potentially life saving oxygen, fluids and antibiotics can be commenced.

This article was written by Janet Brown 16th February 2017