Phosphatemic control during acute renal failure: intermittent hemodialysisversus continuous hemodiafiltration

Background: Achieving "adequacy of dialysis" includes the maintenance of no rmal serum phosphate concentrations and is an important therapeutic goal in the treatment of acute renal failure (ARF). It is unknown whether this goa l is best achieved with intermittent or continuous renal replacement therap y. Methods: We compared the effects of continuous veno-venous hemodiafiltratio n (CVVHDF) and intermittent hemodialysis (IHD) on serum phosphate concentra tions using daily morning blood tests in 88 consecutive intensive care pati ents half of which were treated with IHD and half with CRRT. Results: Mean patient age was 54 +/- 14 years for IHD and 60 +/- 14 years f or CVVHDF(NS). However, patients who received CVVHDF were more critically i ll (mean APACHE II scores: 24.4 +/- 5.1 for IHD vs. 29.2 +/- 5.7 for CVVHDF ; p<0.003). Before treatment, the serum phosphate concentration was 2.04 +/ - 0.16 mmoll L for IHD and 1.96 +/- 0.17 mmoll L for CVVHDF (NS), with abno rmal values in 79.4% of IHD patients and in 64.8% of CVVHDF patients (NS). During treatment, CVVHDF induced a greater reduction in serum phosphate (p= 0.02) during the first 48 hours and conferred superior subsequent control o f hyperphosphatemia (achieved in 64.6% of observations during CVVHDF vs. 41 .8% during IHD; p<0.0001). The serum phosphate concentration was also more likely to be within the normal range during CVVHDF (55.3% vs .36.2%; p<0.00 01). There was a trend toward more frequent hypophosphatemia (9.3% vs. 5.6% ; P<0.1) during CVVHDF. Conclusions: Abnormal serum phosphate concentrations are frequent in ARF pa tients before and during renal replacement, however, normalization of phosp hatemia is achieved more frequently with CVVHDF.