Abdominal Perfusion Pressure as a Prognostic Marker in Intra-abdominal Hypertension

Abstract

Elevated intra-abdominal pressure (IAP) is a continuum from intra-abdominal hypertension (IAH) to abdominal compartment syndrome (ACS) and has considerable impact on end-organ function [1]. However, no data are available on IAP from large prospective clinical trials. Many thresholds have been proposed as the critical value for IAP in guiding decompression. Recent publications have improved our understanding of the pathophysiological mechanisms. We are now aware that even slight elevations in IAP of 10 mmHg may have a tremendous impact on end-organ function [1]. However, it is probably not the absolute value of IAP but the acuity of increase in IAP or the trend over time that is predictive for outcome. Most of the published studies relate to the hemodynamically stable patient or laboratory animal without prior insult. Extrapolation of these results to a critically ill patient or to a trauma patient who may have experienced episodes of shock and resuscitation and hence of ischemia-reperfusion (I/R) injury, may be incorrect. Co-morbidities play an important role in aggravating the effects of raised IAP such as pre-existing chronic renal failure, massive hemorrhage, hypovolemia, positive end-expiratory pressure (PEEP), or pre-existing cardiomyopathy, and these may reduce the threshold of IAH that causes clinical manifestations of ACS. Indeed, the critical IAP value differs from patient to patient and from time to time. A prognostic parameter that could help us in following these patients and guiding therapy would be very helpful. This chapter will focus on abdominal perfusion pressure (APP), defined as mean arterial pressure (MAP) minus IAP, as such a possible parameter.