Evaluation of acute renal failure in surgical patients in the intensive care unit

Background

Acute renal failure (ARF) is a common and serious complication in the postoperative period of critically ill patients. It occurs, depending on specific definition, in up to 30% of patients submitted to cardiac surgery. Recent evidence suggests that even small oscillations in serum creatinine are associated with significant effects on mortality. The objective of this study is to evaluate the impact of ARF on the morbidity and mortality of surgical patients in the ICU.

Methods

A retrospective observational study conducted in the ICU of a public university hospital during the period January 2004–December 2004. The research was realized in an electronic database and included demographic data, diagnostic, SOFA and APACHE II scores, length of stay in the ICU and mortality. The renal dysfunction was defined as a SOFA score ≥2 (creatinine ≥2 mg/dl or oliguria <500 ml/day). Patients with chronic renal failure were excluded. For statistical analysis, the Epi Info program version 3.3.2 was used.

Results

One hundred and five surgical patients were admitted to the ICU in the study period, male sex was more frequent (55.2%), with a mean age of 53.2 years, mean APACHE II score of 17 ± 7, and length of stay varying from 1 to 65 days (median 3 days). The most frequent surgeries were gastrointestinal (16.2%), multiple trauma (13.3%), intracranial hemorrhage (9.5%) and metabolic/renal (9.5%). In this sample the cardiovascular surgery was not representative (2.9%).

ARF occurred in 19% (95% CI: 11.3–26.8%) of the surgical patients and the mortality in this group was greater than in the group of patients that did not develop this complication, respectively 63.2% and 15.1% (P < 0.001). The patients with ARF were older than the patients without this complication (64.9 ± 7.9 years vs 50.6 ± 21.14 years, P < 0.007) and the APACHE II score was higher (20.3 ± 4.9) in the ARF patients when compared with patients without ARF (16.5 ± 7.4, P < 0.06). The median length of stay was higher in the patients with ARF, being 6 days, varying from 3 to 65 days, while in the patients without ARF the median was 2 days, varying from 1 to 33 days (P < 0.001).

Conclusion

The high frequency of ARF found in this study was probably due to the definition criteria adopted, including transient oliguria and pre-renal ARF. The occurrence of renal dysfunction resulted in higher morbidity and mortality in this group of patients. Several studies have been carried out to determine the patients at high risk of developing ARF in the postoperative period, and protective strategies have been developed, but the results are as yet inconclusive.