Continuous Veno-Venous Hemodiafiltration or Hemofiltration: Impact on Calcium, Phosphate and Magnesium Concentrations

Abstract

Background and Objectives Different techniques of continuous renal replacement therapy (CRRT) might have different effects on calcium, phosphate and magnesium concentrations. Accordingly, we tested whether continuous veno-venous hemodiafiltration (CVVHDF) or continuous venovenous hemofiltration (CVVH) would achieve better control of these electrolytes. Design Retrospective controlled study Setting Two tertiary Intensive Care Units Patients Critically ill patients with acute renal failure (ARF) treated with CVVHDF (n=49) or CVVH (n=50) Interventions Retrieval of daily morning ionized calcium, phosphate and magnesium before and after the initiation of CRRT for up to 2 weeks of treatment. Measurements and Results Before treatment, both groups had a high incidence of abnormal ionized calcium concentrations (57.2% for CVVHDF vs 46.0% for CVVH; NS). After treatment, both groups showed a significant increase in serum calcium concentration over the first 48 h (p=0.041 vs p=0.0048) but hypercalcemia was more common during CVVHDF (15.3% vs 0.4%; p<0.0001). However, in both groups, hypocalcemia remained common (30.9% vs 36.7%; NS). Before treatment, abnormal serum phosphate concentrations were also common (65.1% for CVVHDF vs 78.1% for CVVH; NS). After treatment, both groups achieved a significant reduction of serum phosphate within 48 hours (p<0.0001 in both groups). There was no difference in the prevalence of abnormal phosphate levels during treatment (45.5% vs 42.4%; NS). Before treatment, both groups had a high incidence of abnormal magnesium concentrations (50.0% for CVVHDF vs 51.2% for CVVH; NS). During treatment, there was no significant change in serum magnesium concentrations during the first 48 hours or in the prevalence of abnormal magnesium concentrations (56.3% vs 63.4%; p=0.13). However CVVHDF was associated with a higher prevalence of hypomagnesemia (8.1% vs 0.4%; p<0.0001) and a lower incidence of hypermagnesemia (48.2% vs. 63.0%; p=0.0014). Conclusions In critically ill patients with ARF, calcium, phosphate and magnesium were commonly abnormal and they were only partly corrected by CRRT. CVVH and CVVHDF had a different effect on serum magnesium concentrations.