Changing Acute Renal Failure Treatment from Intermittent Hemodialysis to Continuous Hemofiltration: Impact on Azotemic Control

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Abstract
Background: Continuous renal replacement therapy is increasingly used in the management of acute renal failure in critically ill patients. The advantages of continuous renal replacement therapy (CRRT) over intermittent hemodialysis (IHD), however, are not yet fully documented. In particular, it is unknown whether continuous veno-venuous hemodiafiltration (CVVHDF) provides better control of azotemia than IHD. Objectives: To study the effect on azotemic control of changing acute renal failure treatment from IHD to CVVHDF. Settings: Tertiary intensive care unit. Patients: Forty seven consecutive critically ill patients with multiorgan failure and acute renal failure treated with IHD and 47 similar patients treated with CVVHDF. Methods: Analysis of daily morning urea and creatinine concentrations over the period of renal replacement therapy in the ICU. Statistical comparison of data. Results: The two groups of patients were comparable for mean age (55 years for IHD vs. 60 years for CVVHDF; NS) and number of failing organs prior to therapy (mean of 4.2 for IHD vs. 3.7 for CVVHDF; NS). Severity of illness at admission as assessed by APACHE II score, however, was greater for patients receiving CVVHDF (29.4 vs 25.7; p<0.003). CVVHDF was associated with a significantly lower plasma urea (p< 0.0001) and serum creatinine (p<0.01) level at 24 hours of treatment despite similar levels at the start of therapy. Throughout the duration of therapy, mean urea levels (35.0 mmol/L for IHD vs 23.4 mmol/L for CVVHDF) and mean serum creatinine levels (513 micromoles/L for IHD and 263 micromoles/L for CVVHDF) showed significantly (p <0.0001) better control of uremia with CRRT. Conclusions: Changing the form of renal replacement therapy from intermittent hemodialysis to continuous hemofiltration is associated with improved control of azotemia. The superior adequacy of small solute clearance achieved during CVVHDF provides additional support for its preferential use in the management of acute renal failure in the ICU.