The rise in capillary permeabilty allows a fluid shift out of the pulmonary vascular bed to occur leading to the development of pulmonary oedema. There can also be an initial increase in urinary output but this later decreases. This phase is rarely seen today. In this phase the cardiac output falls due to myocardial depression and decreased intravascular volume. Sympathetic responses produce marked vasoconstriction, narrowing of the pulse pressure, and marked sinus tachcardia.
Significant hypotension occurs due to the increased afterload and decreased output.
Skin is pale and cool and the respirations are rapid and shallow. Oxygen delivery is diminished and arterial blood gases reveal combined metabolic and respiratory acidosis with hypoxaemia. Urinary output decreases to the point of oliguria. This phase has a poor prognosis. Anaphylactic Shock which can be classified in the distributive group is characterised by acute changes in vascular permeability and bronchial hyperactivity.