The physiological effects of elevated intra-abdominal pressure following aneurysm repair

Abstract

Objectives: Elevated intra-abdominal pressure (IAP) may cause widespread organ dysfunction (abdominal compartment syndrome) through effects on the respiratory, cardiac, renal and gastro-intestinal systems. The aim of this study was to document IAP following aneurysm surgery, and to determine the effect of IAH on outcome. Design: Prospective observational study. Setting: University Hospital. Subjects: The patient cohort comprised 75 patients undergoing infra-renal aneurysm repair (53 non-ruptured [40 conventional - 1 death, 13 endovascular] and 22 conventionally repaired ruptured AAA - 8 deaths). IAP was quantified by bladder manometry at the termination of the procedure and at 24 h intervals in patients who remained intubated. Physiological indices of organ function were recorded. Statistical analysis utilized the unpaired t-test, Fischer's exact test and Pearson's correlation. Results: IAP was significantly higher at abdominal closure following ruptured aneurysm repair (15.4 mmHg [SE 1.6) than conventional (10.5 [0.89]) or endovascular elective repair (6.4 [1.0]) of non-ruptured AAA. The sensitivity and specificity of IAP to predict subsequent mortality was analysed using a receiver characteristic operating curve. This analysis demonstrated that a cut off of 15 mmHg was the most useful for indicating patients at risk (sensitivity 0.66, specificity 0.79). Physiological indices of organ dysfunction (pH[p = 0.027], base excess [p = 0.005], peak inspiratory pressure [p = 0.0015], CVP and urine output [p = 0.0029]) were significantly impaired in patients with IAP ≥ 15 mmHg, in comparison to patients with lower pressures. IAP correlated significantly with indices of cardiac (CVP p=0.038), respiratory (PaO2/FiO2, p = 0.026), and renal function (urine output p = 0.046). Conclusions: These data suggest that the management of IAH may have a role following repair of ruptured AAA. High intra-abdominal pressures rarely complicate elective or endovascular aneurysm repair.