Immune cells can sense pathogens which results in the initiation of an immune response aimed at eliminating the invading pathogen. When bacteria overcome the ability of the immune system to clear the infection, the interactions between pathogens and immune cells may advance into a deregulated response that no longer benefits the host.
Sepsis is a clinical syndrome caused by a systemic deregulated inflammatory immune response to an infection. The term ‘severe sepsis’ describes instances in which sepsis is complicated by acute organ dysfunction. Severe sepsis have a significant and increasing impact on public health, and is one of the leading causes of mortality in the intensive care units in the developed world.
The incidence of sepsis is increasing due to the aging of the population, an increase of drug-resistant bacteria and weakening of the immune system caused by e.g. HIV infection, cancer treatments or transplant drugs.
While any type of infection (bacterial, viral or fungal) can lead to sepsis, the lung is the leading source of infection both in severe sepsis and in septic shock. Community-acquired pneumonia (CAP) is a common denominator for infections of the lung acquired from normal social contact (i.e. outside of the hospital setting). CAP is a leading cause of death if complicated by the development of sepsis.
In sepsis secondary to CAP the dominant pathophysiologic mechanism of the disease is the hyperactivation of the host systemic inflammatory response against infection leading to high levels of inflammatory mediators provoking systemic vasodilatation (hypotension), micro-vascular thrombosis, and widespread endothelial injury and activation. The necrosis of the tissue due to low perfusion might end in organ failure that, among others, could affect the lung, liver, kidneys, and central nervous system. In the worst cases this leads to the patient´s death making sepsis a life-threatening condition with high mortality rates. In addition, the initial exaggerated activation of immune response is accompanied by progressive reprogramming of the immune response, leading to a state of ‘immunoparalysis’, which is characterized by the occurrence of secondary and opportunistic infections, reactivation of latent viruses and a state of anergy.
LINKS OF INTEREST
- International Sepsis Forum: http://internationalsepsisforum.com
- Society of Critical Care Medicine: http://www.sccm.org
- World Federation of Societies of Intensive and Critical Care Medicine: http://www.world-critical-care.org/
- Sepsis Alliance (SA): http://www.sepsis.org/
- European Societies: http://www.europeanshocksociety.org/
- The European Society of Intensive Care Medicine: http://www.esicm.org/
- Sociedad Española de Medicina Intensiva, Critica y Unidades Coronarias (SEMICYUC): http://www.semicyuc.org/
- Sociedad y Fundación Española de Cuidados Intensivos Pediátricos (SECIP): https://www.secip.com/
- Spanish Edusepsis Network: http://www.edusepsis.org/
- Belgium Society of Intensive Care and Emergency Medicine: http://www.siz.be/
- Societe de Reanimation de Langue Française: http://www.srlf.org/
- French Society of Anesthesia and Intensive Care Medicine (SFAR): http://sfar.org/
- Dutch Society of Intensive Care: https://nvic.nl/