Urea Removal by Hemofiltration and Hemodiafiltration

Abstract

Continuous hemofiltration is usually regarded as a safe method for controlling fluid overload in neonates presenting acute renal failure. We considered that continuous hemodiafiltration with a hemofilter type especially designed for use in the neonatal period could improve urea removal as compared with hemofiltration. Continuous arteriovenous hemofiltration (CAVH) and hemodiafiltration (CAVHD) were consecutively performed on 7 anesthetized adult rabbits which were given an urea infusion. The hemofilter was a 800-cm² polysulfone model (Amicon Minifilter Plus). Mean values for physiological and operational parameters were comparable during CAVH and CAVHD, i.e., mean blood pressure (69.6 ± 14.9 and 70 ± 13.1 mm Hg, respectively), arterial oncotic pressure (16.0 ± 2.4 and 16.0 ± 1.7 mm Hg), hematocrit (36.2 ± 5.8 and 36.7 ± 4.4%), protein plasma level (38.9 ± 7.0 and 39.0 ± 6.4 g/l), urea plasma level (20.6 ± 6.5 and 19.9 ± 7.0 mmol/l), plasma flow in the hemofilter (7.89 ± 8.48 and 7.12 ± 3.08 ml/min), and ultrafiltrate rate (1.17 ± 0.49 and 1.73 ± 0.78 ml/min). CAVHD allowed a significant increase in urea clearance (4.74 ± 4.51 ml/min) as compared with CAVH (1.23 ± 0.81 ml/min). These experimental results suggest that CAVHD usefulness should be assessed in neonates presenting acute renal failure.

Pediatric hemofiltration: Normocarb dialysate solution with citrate anticoagulation

“…Data to date have shown that, in studies comparing CVVH and CVVHD, urea clearance is identical when the total solution exposure is identical. These results have been consistent in other studies [12,16,17].…”

Urea removal by neonatal hemo(dia)filters in hyperazotemic rabbits

“…Thus, urea clearance obtained by HF was close to the ultrafiltrate rate, a finding previously observed with the Minifilter Plus device [15,17], as well as with filters designed for adults and children [18,21]. Thus, urea clearance obtained by HF was close to the ultrafiltrate rate, a finding previously observed with the Minifilter Plus device [15,17], as well as with filters designed for adults and children [18,21].…”

“…The small size of the filters, which are made of hollow fibers with a large inner diameter, and the low filter blood flows associated with neonatal circuits might combine to produce functional characteristics that differ significantly from adult circuits [15,16]. Recently, experimental studies by Werner et al [15,16] failed to demonstrate that urea clearance of a polysulfone filter (Minifilter Plus, Amicon) was increased from HF to HDF, whereas other studies showed some marked improvement [3,5,8,17,18]. Moreover, to the best of our knowledge, the performance of hemo(dia)filters available for neonates has not been previously compared.…”

Duration of extracorporeal therapy in acute maple syrup urine disease: a kinetic model

“…The choice of dialysis modality is influenced by several factors including the goals of dialysis, the advantages and disadvantages of each modality, institutional expertise and resources [10]. Both PICUs in our study used a dialysis method with extracorporeal blood circulation, providing a higher leucine clearance than the one obtained by peritoneal dialysis [11,12]. The French center used CECRT instead of HDi over concerns of possible hemodynamic instability, which may increase risk of neurological damage in patients with cerebral edema, but primarily because CECRT was well established in their institution.…”

“…Sedation and mechanical ventilation were required for 7 of the 11 episodes (Table 1). A hemodialysis catheter (8)(9)(10)(11)(12) French dual lumen catheter depending on patient size) was inserted via the femoral, internal jugular or subclavian vein. Blood samples were drawn every 1-6 h to obtain blood gases, hematocrit and activated clotting time as well as total protein, sodium, potassium, calcium, phosphate, urea, and creatinine levels.…”