Adverse hemodynamic effects of intraabdominal pressure- is it all in the head?

Elevated intraabdominal pressure (IAP) is observed in various clinical situations, the most common of which are severe abdominal trauma and laparoscopic surgery. Extreme pressures may lead to Abdominal Compartment Syndrome (ACS), but even with lower pressures adverse effects are apparent. The cardiovascular system, the respiratory system, the kidneys and the visceral circulation are all affected, but the exact physiological mechanism is not well defined.

To discuss possible mechanisms which explain the observed hemodynamic effects of increased IAP.

Large animal model observations and review of current literature regarding the correlation between IAP and intracranial pressure (ICP).

It was shown that the elevation of abdominal pressure leads to elevation of ICP. Transfer of pressure through the central venous system or by the cerebrospinal fluid (CSF) has been proposed as an explanation. In response to elevated ICP, various stress hormones are secreted by the central nervous system, including vasoconstricting agents such as vasopressin and catecholamines. It is hypothesized that the central nervous system is the link between the increased abdominal pressure and its adverse hemodynamic effects. This may be a protective mechanism of the brain, aimed to increase the mean arterial pressure when the ICP is elevated, in order to preserve the cerebral perfusion pressure.

ICP is elevated in response to IAP elevation, and may be responsible for its adverse hemodynamic effects. Antagonists to vasopressin may have a role in the treatment of this condition.