Increased capillary permeability:

• Capillary wall becomes 'leaky' allowing protein molecules (albumin) to pass through into the interstitial space, drawing water with them and the patient becomes oedematous
• The effect can also happen in the lung causing acute respiratory distress syndrome (ARDS)

Capillary leak, resulting in:

• Loss of fluid from blood stream
• Oedema
• Drop in blood pressure
• Rise in heart/respiratory rates
• Initially bounding pulse, becoming weaker
• Decreasing urine output

Inappropriate vasodilation:

• Toxins cause peripheral vasodilation
• As a result of reduced circulating volume, this creates impaired oxygen perfusion to the tissues, leading to organ dysfunction and failure

Tissue hypoxia results in:

• Anaerobic metabolism - this process releases oxygen for metabolism but also lactate causing metabolic acidosis
• Lactate metabolism

Disseminated Intravascular Coagulation (DIC)

• Micro-circulatory changes can lead to pooling and stasis of blood that predisposes to platelet aggregation (clots)
• DIC is often seen in patients with septic shock with very rapid consumption of clotting factors
• This leads to bleeding, particularly from mucosal surfaces