Intra-abdominal hypertension and acute renal failure in critically ill patients.

OBJECTIVE: To investigate the relationship between intra-abdominal hypertension (IAH) and acute renal failure (ARF) in critically ill patients. DESIGN AND
SETTING: Prospective, observational study in a general intensive care unit. PATIENTS: Patients consecutively admitted for >24 h during a 6-month period.
INTERVENTIONS: None. MEASUREMENTS AND
RESULTS: Intra-abdominal pressure (IAP) was measured through the urinary bladder pressure measurement method. The IAH was defined as a IAP > or =12 mmHg in at least two consecutive measurements performed at 24-h intervals. The ARF was defined as the failure class of the RIFLE classification. Of 123 patients, 37 (30.1%) developed IAH. Twenty-three patients developed ARF (with an overall incidence of 19%), 16 (43.2%) in IAH and 7 (8.1%) in non-IAH group (p<0.05). Shock (p<0.001), IAH (p=0.002) and low abdominal perfusion pressure (APP; p=0.046) resulted as the best predictive factors for ARF. The optimum cut-off point of IAP for ARF development was 12 mmHg, with a sensitivity of 91.3% and a specificity of 67%. The best cut-off values of APP and filtration gradient (FG) for ARF development were 52 and 38 mmHg, respectively. Age(p=0.002), cumulative fluid balance (p=0.002) and shock (p=0.006) were independent predictive factors of IAH. Raw hospital mortality rate was significantly higher in patients with IAH; however, risk-adjusted and O/E ratio mortality rates were not different between groups.
CONCLUSIONS: In critically ill patients IAH is an independent predictive factor of ARF at IAP levels as low as 12 mmHg, although the contribution of impaired systemic haemodynamics should also be considered.