Abstract
IntroductionThe best modality, for continuous renal replacement therapy (CRRT) is currently uncertain and it is poorly understood how transport of different solutes, whether convective or diffusive, changes over time.MethodsWe conducted a prospective cross over study in a cohort of critically ill patients, comparing small (urea and creatinine) and middle (β2 microglobulin) molecular weight solute clearance, filter lifespan and membrane performance over a period of 72 hours, during 15 continuous veno-venous dialysis (CVVHD) and 15 continuous veno-venous hemofiltration (CVVH)sessions. Both modalities were administered based on a prescription of 35 ml/kg/h and using polyacrylonitrile filters.ResultsMedian filter lifespan was significantly longer during CVVHD (37 hours, interquartile range (IQR) 19.5 to 72.5) than CVVH (19 hours, IQR 12.5 to 28) (p = 0.03). Median urea time weighted average (TWA) clearances were not significantly different during CVVH (31.6 ml/minute, IQR 23.2 to 38.9) and CVVHD (35.7 ml/minute, IQR 30.1 to 41.5) (p = 0.213). Similar results were found for creatinine: 38.1 ml/minute, IQR 28.5 to 39, and 35.6 ml/minute, IQR 26 to 43 (p = 0.917), respectively. Median β2m TWA clearance was higher during convective (16.3 ml/minute, IQR 10.9 to 23) than diffusive (6.27 ml/minute, IQR 1.6 to 14.9) therapy; nonetheless this difference did not reach statistical significance (p = 0.055). Median TWA adsorptive clearance of β2m appeared to have scarce impact on overall solute removal (0.012 ml/minute, IQR -0.09 to 0.1, during hemofiltration versus -0.016 ml/minute, IQR -0.08 to 0.1 during dialysis; p = 0.79). Analysis of clearance modification over time did not show significant modifications of urea, creatinine and β2m clearance in the first 48 hours during both treatments. In the CVVHD group, the only significant difference was found for β2m between 72 hours and baseline clearance.ConclusionPolyacrylonitrile filters during continuous hemofiltration and continuous hemodialysis delivered at 35 ml/kg/h are comparable in little and middle size solute removal. CVVHD appears to warrant longer CRRT sessions. The capacity of both modalities for removing such molecules is maintained up to 48 hours.
Highlights
The best modality, for continuous renal replacement therapy (CRRT) is currently uncertain and it is poorly understood how transport of different solutes, whether convective or diffusive, changes over time
Median β2m time weighted average (TWA) clearance was higher during convective (16.3 ml/minute, interquartile range (IQR) 10.9 to 23) than diffusive (6.27 ml/minute, IQR 1.6 to 14.9) therapy; this difference did not reach statistical significance (p = 0.055)
Polyacrylonitrile filters during continuous hemofiltration and continuous hemodialysis delivered at 35 ml/ kg/h are comparable in little and middle size solute removal
Summary
The best modality, for continuous renal replacement therapy (CRRT) is currently uncertain and it is poorly understood how transport of different solutes, whether convective or diffusive, changes over time. Many intensivists and nephrologists β2m = β2 microglobulin; ARF = acute renal failure; CRRT = continuous renal replacement therapy; CVVH = continuous veno-venous hemofiltration; CVVHD = continuous veno-venous dialysis; IQR = interquartile range; TWA = time weighted average; UF = ultrafiltration. Many studies have used continuous hemofiltration for this purpose, following the expectation that a wider range of molecular weights can be cleared with predominantly convective rather than predominantly diffusive techniques [35]. This notion, based on several in vitro experiments and experience in chronic dialysis [6], has never been tested by a comparative study during the course of continuous extracorporeal treatment
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