Intra-abdominal pressure and renal function after surgery to the abdominal aorta.

It has been suggested that an elevated intra-abdominal pressure (IAP) can impair renal function. In a prospective longitudinal study, the IAP of 42 patients admitted to an intensive care unit after abdominal aortic surgery was monitored. When compared with the other patients, the 22 patients (53%) who developed renal impairment had higher IAP (17.8 +/- 6.0 mmHg versus 14.1 +/- 4.8 mmHg; P less than 0.01) and APACHE II scores (15.6 +/- 6.0 versus 9.8 +/- 4.6; P less than 0.01). Each of the 10 patients who were re-explored because of haemodynamic instability and oliguria had an IAP of greater than 18 mmHg (positive predictive value = 85%, negative predictive value = 62%). Following re-exploration, the urinary output increased by 115 +/- 40 mL/h (P less than 0.01), and the IAP decreased by 10 +/- 3 mmHg (P less than 0.01). Although it is concluded that an IAP greater than 18 mmHg is a significant risk factor for the development of impaired renal function, it was not possible to prove a causal relationship between these events. Nevertheless, such a relationship has been demonstrated in animal and human models.