Renal Replacement Therapy in Acute Renal Failure: Which Index is Best for Dialysis dose Quantification?

Abstract

The "delivered dose" of dialysis may significantly affect the outcome of acute renal failure (ARF) patients requiring dialysis. Our study aimed to elucidate which dose quantification method offers an appropriate parameter to compare different treatments in ARF patients. Six sustained low-efficiency daily dialysis (SLEDD), and 7 continuous venovenous hemofiltration (CVVH) patients with a prescribed Kt/V of 1.0 were studied during a single treatment. CVVH was studied over the first 24 hours after initiation. SLEDD was performed for 6-12 h. Solute clearance (K) was determined by direct dialysate quantification (DDQ). The single-pool Kt/V (spKt/V), equilibrated Kt/V (eqKt/V), equivalent renal urea clearance (EKRc), and solute removal index (SRI) were calculated. There were no significant differences at enrollment between the SLEDD and the CVVH groups in any patient characteristics except for the serum creatinine levels. The prescribed Kt/V of both groups was similar (SLEDD, 0.9+/-0.22; CVVH, 1.10+/-0.12, p=NS). The EKRc, which is used to verify kinetic equivalence among patients treated with differing renal replacement therapies (RRT), was higher in CVVH (15.7 in SLEDD; 27.4 in CVVH, p<0.0001), despite the fact that there was no difference between the delivered spKt/V for the SLEDD (1.05+/-0.40) and the CVVH (1.10+/-0.11) groups. The values for SRIurea (0.61 in SLEDD; 1.04 in CVVH, p=0.001), SRIcreatinine (0.55 in SLED; 1.02 in CVVH, p<0.0001), and SRIphosphate (1.81 in SLED; 3.60 in CVVH, p=0.03) were higher in CVVH. The EKRc is calculated assuming a steady state, which is an incorrect assumption in ARF patients with hypercatabolism. The SRI calculated using direct dialysate effluent quantification appears to be more reliable as an index of the dialysis dose compared to other methods in ARF patients. However, the use of the dialysate-side SRI is limited by the difficulty of dialysate effluent collection.