Incidence, risk factors and prognostic factors of acute renal failure in patients admitted in an intensive care unit

Purpose

To assess the incidence, risk factors, impact in clinical outcome and prognostic factors of acute renal failure (ARF) in patients admitted to an intensive care unit (ICU).

Methods

All patients admitted to the ICU with a length of stay greater than 48 hours were prospectively followed. ARF was defined by a serum creatinine higher than 1.5 mg/dl. The Acute Physiology and Chronic Health Evaluation (APACHE) II score, LODS score, preadmission and admission characteristics, and clinical evolution were registered. The results were analyzed by t test, Wilcoxon test and, in multivariate analysis, logistic regression and discriminant analysis. They were considered significant if P < 0.05 or if the confidence interval differs from one.

Results

The incidence of ARF was 19.0%, with a mortality of 76.19%. Risk factors to the development of ARF were gender (male, P = 0.053), surgical complications (P = 0.035), higher volume replacement, bleeding and hypotension during surgery (P = 0.017, P = 0.008 and P = 0.044, respectively), risk of death (APACHE II, P = 0.049), LODS (P = 0.006), systemic inflammatory response syndrome (SIRS)/sepsis and shock (P = 0.0001 and P = 0.0001), respiratory failure (P = 0.001), use of norephinephrine (P = 0.003), and serum creatinine and urea at admission (P = 0.0007 and P = 0.0478). In the multivariate analysis, only male gender (odds ratio [OR] = 4.275), heart rate at admission (OR = 1.023), shock owing to SIRS/sepsis (OR = 8.590), higher volume replacement during surgery (OR = 1.002) and serum urea levels at admission (OR = 1.012) remained significant. The prognostic factors of mortality were shock owing to SIRS/sepsis (P = 0.0001), respiratory failure (P = 0.021), highest level of serum potassium (P = 0.013) and lowest level of serum bicarbonate (P = 0.037). In the multivariate analysis, only the highest level of serum potassium remained significant (P = 0.037).

Conclusions

The incidence, morbidity and mortality of ARF in the ICU are high. The main factors associated with its development and prognosis are those associated with hemodynamic instability, suggesting that ARF is a part of multiple organ dysfunction syndrome.