Intra-abdominal hypertension: pulmonary and cerebral complications.

Intra-abdominal hypertension causes many physiologic changes, primarily by reducing thoracic compliance and secondarily causing organ failure, which is the body's normal response to trauma or acute inflammatory response. Compartment syndrome as a cause of abdominal hypertension has adverse effects on the circulation, threatening the function and viability of tissues. Intra-abdominal hypertension with the clinical picture of compartment syndrome is a reperfusion injury that is a cyclic event. Elevated intra-abdominal pressure due to whatever mechanism affects all intra-abdominal viscera, including the abdominal wall. Due to edema reducing thoracic compliance, producing severe encephalopathy and leading to severe ischemia with generation of significant quantities of reactive oxygen free radicals as well peroxidation products released from the intestine, liver and spleen. Elevated intracranial pressure causes encephalopathy and the risk of neuronal damage due to the sharp decrease in cerebral perfusion pressure. Elevated intracranial pressure is due to restriction of outflow from the lumbar venous plexus. The etiology of the sudden increase in capillary permeability remains unclear. Decompressive laparotomy leads to a rapid improvement in pulmonary parameters and oxygen delivery. The clinical state after decompression is an example of ischemia-reperfusion injury requiring therapy with inotropes and other agents to improve cardiac, respiratory, renal and cerebral hemodynamics with life saving effects.