Sepsis is a generalised inflammatory response to infection. Systemic inflammatroy response syndrome (SIRS) can occur in many conditions other than sepsis as well.
Low tidal volume ventilation is useful in ARDS. Activated protein C is useful in severe sepsis, especially if Apache score is more than 25.
Severity of sepsis
Sepsis with organ dysfunction is considered severe sepsis: 25 -30% mortality. If there is significant hypotension, it is called septic shock: 60 -70% mortalitly.
Increase in oxygen extraction in a normal individual occurs due to “capillary recruitment”. But in severe sepsis, this does not work due to microcirculatory derangements. Capillaries are blocked due to platelet thrombi as a consequence of the activation of the coagulation cascade. There is a primary oxygen extraction failure. This can be addressed by giving activated protein C, as was shown in the PROWESS trial. But the drug is very costly.
Cytopathic hypoxia, another reason for oxygenation failure, is due to mitochondrial dysfunction.