ACUTE RENAL FAILURE IN THE INTENSIVE CARE UNIT: Therapy Overview, Patient Risk Stratification, Complications of Renal Replacement, and Special Circumstances

Acute renal failure (ARF) in the intensive care unit (ICU) carries with it a mortality rate ranging from 50% to 70%, especially in the setting of multiple-organ dysfunction or need for dialysis. 63,91,141 Lewis and coworkers 80 recently reported 58% survival in ICU ARF patients, with 16% requiring long-term dialysis support. Although the mortality rate does not appear to be any better than that reported two decades ago, evidence for improving trends in ICU ARF survival has been observed. 134 McCarthy 90 recently noted a significantly improved hospital survival rate (52% versus 32%) in a retrospective comparison of 71 consecutive ICU patients with ARF from 1977 to 1979 and 71 similar consecutive patients from 1991 to 1992. Similarly, Spurney et al 124 found that, of 26 patients who developed ARF requiring renal replacement therapy, 88% recovered sufficient renal function to discontinue dialysis despite prolonged support (mean duration 8.4 ± weeks). The persistent mortality rate has been attributed to several reasons, including a reduction of cases with uncomplicated ARF and an increase in multiple-organ dysfunction syndrome, as well as increasing invasive interventions for diagnostic and therapeutic purposes. 63,103 Moreover, increasing patient age and existence of prior chronic disease are not uncommon findings in the ICU population. 90 Early involvement of the nephrologist is crucial; the mortality rate is increased in ICU patients with ARF when renal consultation is delayed greater than 48 hours (79.3 ± 15% versus 42.0 ± 11.9% within 48 hours of admission, P P 91 Whereas it has been shown that there is a significant independent influence of delivered hemodialysis dose upon survival in ICU patients with ARF, it is unclear whether dialysis per se has made a substantial difference in survival in this population. 91,129,134 Gillum and coworkers 40 have shown that intensive dialysis to maintain blood urea nitrogen (BUN) less than 60 mg/dL and serum creatinine less than 5 mg/dL offers no survival advantage over nonintensive hemodialysis. 40 Moreover, intermittent hemodialysis has been implicated in prolonging the course of ARF by means of repeated hemodynamic insults. 24,98 Theories to explain declining renal function with hemodialysis have cited a number of putative causes, including loss of autoregulation of renal blood flow secondary to dialysis-induced hypotension, loss of the osmotic drive to diuresis, and the properties of the hemodialysis membrane. 46 There have been several recent reviews of continuous dialytic therapy in patients with ARF and the reader is referred to them for a more extensive explanation of basic theory and outcomes. 21,59,86 The purpose of this article is to review some of the lesser known aspects of acute dialytic support, including a review of the nonrenal uses of continuous renal replacement techniques.