The pathophysiology of the acute compartment syndrome

The acute compartment syndrome is a condition in which increased pressure within a limited space compromises the circulation and function of the tissues therein, resulting in tissue ischaemia, necrosis and nerve damage. This rise in tissue pressure originates in a decrease of the compartment size or increase of the intracompartmental volume by oedema and/or haemorrhage. Following the arterio-venous gradient theory, capillary blood flow may be impaired through increased venous pressure, decreased arterial pressure and increased peripheral vascular resistance. Often, compartment syndromes develop during reperfusion following a period of ischaemia. During ischaemia, there is a gradual depletion of intracellular stores of high energy phosphate bonds and glycogen stores. There is a buildup of products of glycolysis, particularly lactic acid, with accompanying hydrogen ion accumulation as well as an increase in intracellular reducing agents. Reperfusion may, instead of restoring normal muscle metabolic activity, cause harmful effects by washing out necessary precursors for adenine nucleotide resynthesis. Production of oxygen free radicals occurs with ensuing lipid peroxidation, and calcium influx occurs upon reoxygenation with resultant disruption of oxidative rephosphorylation in the mitochondria. Furthermore, several lines of evidence suggest that white blood cells are important in the pathogenesis of reperfusion injury. Upregulation of both neutrophil receptors and endothelial leucocyte adhesion molecules leads to the sequestration of white blood cells in the muscle with prolongation of the reperfusion injury. This subsequently results in damage to remote organs such as lungs, liver, heart and kidneys.