Intermittent versus continuous renal replacement therapy in the ICU: impact on electrolyte and acid-base balance

Objectives: The maintenance of normal serum sodium, potassium and bicarbona te concentrations is a therapeutic goal of renal replacement therapy (RRT) in acute renal failure (ARF). The aim of this study was to determine whethe r this goal is best achieved with intermittent hemodialysis (IHD) or contin uous venovenous hemodiafiltration (CVVHDF). Design: Retrospective controlled study. Setting: Tertiary intensive care unit. Patients: Consecutive patients with ARF treated with IHD (n = 47) or CVVHDF (n = 49). Interventions: Measurement of daily morning sodium, potassium and bicarbona te concentrations after the initiation of RRT for up to 2 weeks of treatmen t. Measurements and results: Before RRT, abnormal thigh or low) values were fr equently observed for sodium (42.6% vs 39.6%; NS) potassium (23.4% vs 45.8% ; NS) and bicarbonate (63.2% vs 54.3%; NS). After treatment, however, CVVHD F, but not IHD, significantly increased mean sodium concentrations (p = 0.0 001). CVVHDF was also more likely to normalize the serum sodium than IHD (7 6.2% vs 47.8% p = 0.0001). The mean potassium concentrations of both groups significantly decreased (p = 0.019 vs p = 0.0075, difference: NS). However , CVVHDF more frequently reduced the incidence of hypokalemia (1.9% vs 7.1% , p = 0.0006). CVVHDF but not IHD significantly increased mean bicarbonate concentrations (p = 0.016) in the first 48 h, and more frequently normalize d them (71.5% vs 59.2, p = 0.0073). Conclusions: Serum sodium and potassium, and arterial bicarbonate, concentr ations are frequently abnormal in ARF patients before and during renal repl acement. Normalization of these values, however, is achieved more frequentl y with CVVHDF than with IHD.