Acutely increased intra-abdominal pressure causes a significant increase in intracranial pressure and a decrease in cerebral perfusion pressure. Increased intra-abdominal pressure appears to produce this effect by augmenting pleural and other intrathoracic pressures and causing a functional obstruction to cerebral venous outflow via the jugular venous system. It is possible that the same phenomenon may be why persons with chronically increased intra-abdominal pressure, such as the morbidly obese, suffer from a high frequency rate of idiopathic intracranial hypertension.

The cardiopulmonary effects of acutely elevated intra-abdominal pressure (IAP) were studied in a porcine model to help define more clearly IAP effects in patients with trauma. IAP was increased in six anesthetized swine by intra-abdominal instillation of isotonic ethylene glycol up to an IAP of 25 mm Hg above baseline. Systemic and pulmonary hemodynamic parameters were measured, as well as the effects on bladder pressure, pleural pressure, and pulmonary function. At IAP of 25 mm Hg above baseline, intravascular volume expansion with saline was administered to return the cardiac index (CI) to baseline. Raising IAP correlated with measured bladder pressures (r = 0.9, p = 0.001). At IAP of 25 mm Hg, CI was significantly decreased (p < 0.05, analysis of variance (ANOVA); 3.6 +/- 0.3 vs. 2.2 +/- 0.3 L/min/m2); whereas wedge, pulmonary arterial, and pleural pressures were all elevated (p < 0.05, ANOVA). However, transarterial wedge pressure (wedge--pleural pressure) declined nonsignificantly with increasing IAP. Raised IAP caused impaired pulmonary function with a decreased (p < 0.05, ANOVA) PaO2 and increased (p < 0.05, ANOVA) PaCO2. Despite the elevated wedge pressure, fluid resuscitation returned CI to baseline. These data clarify the hemodynamic changes associated with raised IAP and indicate that care must be taken in interpreting hemodynamic measurements to determine intravascular fluid status in patients with elevated IAP.

Elevated IAP increases ICP and decreases CPP and cardiac index. Volume expansion further increases ICP yet improves CPP via its greater positive effect upon mean arterial pressure (*p < 0.05, analysis of variance. All measurements are mean +/- SEM in mm Hg).

Acute abdominal compartment syndrome has recently been shown to raise intracranial pressure (ICP). This may increase the risk of ischemic neuronal damage by decreasing cerebral perfusion pressure. We report the successful management of a patient with severe multisystem injury in whom abdominal decompression dramatically reduced high ICP unresponsive to medical measures.