Ionized serum calcium levels during acute renal failure: Intermittent hemodialysis vs. continuous hemodiafiltration

Background: Achieving "adequacy of dialysis" includes the maintenance of normal serum ionized calcium concentrations and is an important therapeutic goal in the treatment of acute renal failure (ARF). It is unknown whether this goal is best achieved with intermittent or continuous renal replacement therapy. Methods: We compared the effects of continuous veno-venous hemodiafiltration (CVVHDF) and intermittent hemodialysis (IHD) on serum ionized calcium concentrations using daily morning blood tests in 88 consecutive intensive care patients of which half were treated with IHD and half with CRRT. Results: Mean patient age was 54 +/- 14 years for IHD and 60 +/- 14 years for CVVHDF (NS). However, patients who received CVVHDF were significantly more critically ill (mean APACHE II scores: 24.4 +/- 5.1 for IHD vs. 29.2 +/- 5.7 for CVVHDF, p < 0.003). Before treatment, the mean ionized calcium concentration was 1.177 +/- 0.03mmol/l for IHD and 1.172 +/- 0.04mmol/l for CVVHDF (NS). with abnormal values in 51.6% of IHD patients and in 68% of CVVHDF patients (NS). During treatment. hypocalcemia was significantly more common among CVVHDF patients (24.5% vs. 14.9% p < 0.011) while hypercalcemia was more frequent during IHD (36.1% vs. 25.6%, p<0.019). Conclusions: Abnormal serum ionized calcium concentrations are frequent in ARF patients before and during renal replacement. Once dialytic therapy is applied. CVVHDF is more likely to lower serum calcium concentrations, while IHD is more likely to induce hypercalcemia. Appreciation of these different biochemical effects may assist clinicians in adjusting dialytic therapy in selected patients.