TABLE 3.

Skin stages of a vascular occlusion

SKIN STAGES OF AN OCCLUSION	PATHOPHYSIOLOGY	TYPICAL ONSET AND DURATION
Stage 1: Pallor	Immediate blockage of the arteriole leading to an abrupt interruption in blood flow and tissue perfusion	Instant, lasting a few seconds, or may persist
Stage 2: Livedo reticularis	Build-up of deoxygenated blood within the venous network surrounding	Can occur rapidly and last 24-36 hours
Stage 3: Pustules	Reduction in pH, sweat production, and metabolic changes allowing Staphylococcus aureus to over grow as a facultative aerobe	72 hours
Stage 4: Coagulation (This may occur before Stage 3, at the same time, or pustular overgrowth may mask tissue damage below. This stage indicates necrotic changes)	Tissue blackens due to worsening hypoxia. Cell lysis and outpouring of blood into the tissues. Tissue is firm with retained architecture as a function of the coagulative necrotic process	Occurs over a number of days
Stage 5: Devitalised tissue Stage 5a: Slough Stage 5b: Eschar	Destruction of the tissues and a build-up of denatured structural proteins (collagen, fibrin, elastin), neutrophils, bacteria and haemoglobin. Slough is moist and is creamy/yellow or green. Ecshar is black (dark) and dry.	Days