Intra-abdominal pressure and cardiovascular system in the intensive care unit patient

Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) are frequently observed in patients admitted to the intensive care unit and are associated with significant morbidity and mortality. IAH and ACS may interact with the cardiovascular system, involving the three components of cardiac function: ventricular preload, ventricular afterload, and myocardial contractility. In critically ill patients, increase in intra-thoracic pressure and cephalic shift of diaphragm may induce a decrease in cardiac output secondary to the reduction in venous return and in cardiac contractility associated with an increase in ventricular afterload which predominantly involves the right ventricle. A significant reduction in renal output, hepatosplanchnic output, and cerebral venous return are simultaneously observed. Dynamic tests of volume responsiveness remain valid in mechanically ventilated patients with IAH. However, physicians should keep in mind that the best threshold for fluid responsiveness regarding pulse pressure variation is probably higher in patients with IAH than in patients with normal intra-abdominal pressure. This assumption is essential since dynamic tests regarding volume responsiveness are useful in patients with IAH to prevent overload and ACS onset leading to multiple organ failure. In any case and when it is possible, emergent abdominal decompression should be performed.