Intra‐abdominal hypertension and the abdominal compartment syndrome

The adverse effects of increased intra-abdominal pressure (IAP) were first documented in the second half of the 19th century but, only recently, has it been recognised as a major cause of morbidity in critically ill patients. Normally, IAP reflects intrathoracic pressure and its value is zero or slightly sub-atmospheric. Mild elevation of IAP (3‐15 mmHg) may be seen during mechanical ventilation, after surgery or in the obese. A compartment syndrome occurs when the pressure within a closed abdominal compartment is increased to a level where the blood flow to its contents is compromised and the viability of the tissues is threatened. The threshold for the development of an abdominal compartment syndrome (ACS) varies with the status of the intravascular fluid and the compliance of the abdominal wall. Mild elevation of IAP may be compensated by fluid resuscitation. At IAP of 25 mmHg, a syndrome of cardiovascular, renal and pulmonary dysfunction develops. As IAP increases further, multi-organ dysfunction may finally result in cardiovascular collapse and death. Prompt recognition of the syndrome, coupled with fluid resuscitation and surgical decompression, is the key to successful management.