Acute renal failure in obstetrics: risk factors and outcome

Introduction

Acute renal failure (ARF) was newly recognized as a specific mortality risk factor [1] and is in general associated with a high mortality rate.

Hypothesis

Identifying risk factors for ARF could help reduce mortality. We shall try to describe them in critically ill obstetric patients, and explain ARF association with multiple organ failure (MOF) and outcome using the Sequential Organ Failure Assessment (SOFA) score and Logistic Organ Dysfunction (LOD) score.

Methods

An open prospective observational cohort study in a multidisciplinary ICU. All critically ill obstetric patients were analysed unless diagnosed with chronic renal failure or kidney transplant. ARF was defined as serum creatinine ≥ 100 μmol/l and/or urine output ≤ 500 ml/day and/or doubling of baseline serum creatinine levels.

Results

Six hundred and forty patients were reviewed (mortality rate 13.3%). ARF was diagnosed in 223 patients. Main risk factors present at admission were: acute circulatory failure, transfusion and association with haemolysis elevated liver enzyme and low platelet count (HELLP) syndrome. ARF patients with HELLP syndrome on admission were most likely to develop and alter multiple organ dysfunctions/failures. ARF is associated with an elevated relative risk of mortality (x1.5). Anuria and a serum creatinine level > 300 μmol/l were independent risk factors for mortality (OR 2 and 7, respectively). The ICU mortality of ARF patients increased with the number of failing organs on admission, especially persistent circulatory failure over time. The LOD score is at least as good as the SOFA score in evaluating the association MOF–ARF with mortality. In fact, LOD cutoff values defining cardiovascular, respiratory hepatic and hematologic organ failures fit particularly our obstetric population.

Conclusion

Most important risk factors for ARF or mortality are often present on admission. During the ICU stay, other organ failures (especially cardiovascular) are important risk factors to develop or alter renal function, especially persistence of circulatory shock; thus, aggressive fluid challenge and volume infusion policy could help ARF prevention. HELLP syndrome and ARF is a particularly morbid association because of accumulating organ failures.