Aluminum kinetics using bicarbonate dialysate with the sorbent system.

In the REDY system a sorbent cartridge is used to regenerate the spent hemodialysate so that only six liters of dialysate are required for a treatment. The manufacturer claims that the cartridge can be used to remove aluminum from the dialysate and that it does not add aluminum to the dialysate. This claim for acetate dialysate is supported by the literature, but there are few data available relative to bicarbonate dialysate. The present study evaluates the use of bicarbonate dialysate and the REDY system in regard to aluminum kinetics both in vitro and in vivo. In vitro, the sorbent cartridge removed aluminum from dialysate prepared from water containing as much as 470 micrograms/liter of aluminum, giving a dialysate containing less than 10 micrograms/liter. The first 500 ml of effluent contained 13 micrograms/liter of aluminum but after filtration decreased to below 10 micrograms/liter. Thus, it is unnecessary, as recommended, to discard the first effluent since this unfilterable aluminum will not pass through a dialysis membrane. In vivo, in a crossover study comparing the REDY with single pass, there were no significant differences between the pre- and post-plasma aluminum concentrations, and the dialysate aluminum remained below 4 micrograms/liter during the dialysis. In a second in vivo study the effect of dialysate from tap water on plasma aluminum using the predialysis purification procedure was evaluated. There was no differences between the pre- and post-plasma aluminum concentration. The aluminum levels were comparable to those of the crossover study. The dialysate remained below 4 micrograms/liter during the dialysis.

Erythropoietin alert: risks of high hematocrit hemodialysis.

The impending release of erythropoietin (EPO) is expected to result in a dramatic increase in hematocrit (Hct) for most hemodialysis (HD) patients. Our studies indicate that as Hct rises, dialyzer mass transport for some clinically critical solutes will be adversely affected. When whole blood clearances are corrected for solute-specific blood-water flows (QBH2O), the effect on the surrogate molecule, urea, used in urea kinetic modeling (UKM) is deceptively minimal, because only urea can diffuse almost instantly from red cells into blood water. For the critical solutes, potassium and phosphate, QBH2O is reduced to Q (plasma water). With a KoA of 690 ml/min at QB = 300, clearance of potassium falls at least 19.3% as Hct rises from 20 to 40% so that steady-state predialysis potassium could rise from 6.0 to 6.95 mEq/L. Already inadequate phosphate clearance falls at least 10% and additional loss results from physical interference by RBCs with solute diffusion. Hcts are further increased with rapid weight losses during high-efficiency dialyses (0.15 per 5% weight loss in 3 hours, r = 0.82) resulting in blood-side pressures such that most dialysis machines cannot provide adequate dialysate pressures to maintain low ultrafiltration rates (UFRs) at the high QB levels. The combination of pre-existing diffuse vascular disease, postdialysis hypovolemia, hypotension, decreased cardiac output, and increased blood viscosity has and will produce disastrous syndromes of organ ischemia, thrombosis, and infarction. Predialysis hypertension can worsen. Extreme caution and adjustment of dialysis regimen is necessary as patient Hct rises above 36%.

In vivo analysis of the Lundia 5 (PRO 5) and Lundia 3 (PRO 3) dialyzers with Gambrane polycarbonate membranes.

The physical, solute transfer and biocompatibility properties of two new parallel plate dialyzers using Gambrane polycarbonate (PC) membrane of 0.8 m2 (L-3 PC) and 1.1 m2 (L-5 PC) were studied in 6 volunteer chronic dialysis patients. Two of these 6 had suffered severe first-use syndromes with Cuprophan. Samples were collected under carefully controlled conditions. Mass transport properties were confirmed by total dialysate collection and found to compare favorably with other standard dialyzers. For the L-3 PC, KUF was 3.59 ml/h/mm Hg TMP-14.5 and standard whole blood clearances were BUN 142, creatinine 121 and inorganic phosphate 69 ml/min. For the L-5 PC, KUF was 6.27 ml/h/mm Hg TMP-28.66 and standard clearances were BUN 155, creatinine 134 and inorganic phosphate 89 ml/min. Using bicarbonate dialysate no consistent hypoxemia occurred and all dialyses were well tolerated. The L-3 PC and L-5 PC dialyzers induced more leukopenia and C3a generation than PAN but less than Cuprophan. Thus these new dialyzers offer conventional mass transfer and ultrafiltration rates with much improved membrane biocompatibility.

Effect of ethanol on choline transport in rat jejunum.

The effect of ethanol on choline transport across the rat jejunum was studied by intraluminal perfusion in vivo and by influx measurement across the brush-border membrane in vitro. Acute ethanol administration (4 g/kg) through a gastric tube caused an increase in net choline absorption within 1 h. The increase was prevented by pretreatment with pyrazole, an inhibitor of ethanol metabolism. Chronic ethanol administration also caused an increase in choline absorption, the effect being unrelated to the nutritional changes that occur with ethanol ingestion. In contrast, direct instillation of 0.65 M ethanol through the perfusate caused no changes in choline absorption, and the perfusion of a 1.14 M solution even decreased absorption. The in vitro influx of choline across the mucosal membrane of the isolated rat jejunum was also enhanced by pretreatment with ethanol given by gavage 1 h prior to experimentation. Similarly, the ethanol-related increase in the influx rate was inhibited by pyrazole but was unaffected by acetaldehyde or acetate. Like ethanol, pretreatment of rats with methanol stimulated the choline influx rate. The results suggest that ethanol metabolism, rather than the direct effect of ethanol by itself, stimulates the absorption and influx of choline into the rat jejunum. The effect is not produced by the primary metabolites of ethanol, acetaldehyde, or acetate but is very likely related to stimulation by other products of ethanol metabolism.

Performance characteristics of high flux haemodiafiltration.

With the described technique of high diffusive and convective solute transport an almost threefold increase in efficiency over conventional dialysis was clinically demonstrated. Coupled with the better tolerance to high solute and weight removal rates, this approach permits drastic reduction of treatment time, without sacrificing treatment adequacy.

High-flux hemodiafiltration: under six hours/week treatment.

Better utilization of existing high blood flow in mature vascular accesses with the described new technique of simultaneous high diffusion and convection results in a marked increase of treatment efficiency. Coupled with the better tolerance to high solute and weight removal rates, this approach permits drastic reduction of treatment time over conventional hemodialysis without sacrificing treatment adequacy.

Technical aspects of high-flux hemodiafiltration for adequate short (under 2 hours) treatment.

The efficiency of hemodialysis can be more than doubled. This involves deviating from conventional blood and dialysate flows, employing dialyzers with greater surface area and permeability, bicarbonate dialysate, and an apparatus capable of rigid volumetric control of the dialysate. Coupled with the better treatment tolerance described elsewhere in this volume, this self-contained and automated technique providing high diffusive and convective transfer permits drastic reductions in treatment time over conventional dialysis: in our study, to under 6 hrs/wk.

Pancreatic ascites: an unusual complication of hyperparathyroidism.

Pancreatic ascites is usually considered to be a sequela of chronic alcoholic pancreatitis. Our patient had pancreatic pseudocyst formation and pancreatic ascites after acute pancreatitis, the latter secondary to hypercalcemic pancreatitis and documented hyperparathyroidism.

A volume controlled apparatus for ultrafiltration and hemofiltration with acetate or bicarbonate solutions.

To meet a growing need, a single dialysis apparatus has been developed that can easily be employed by conventionally trained staff to perform volume programmed ultrafiltration hemodialysis, sequential ultrafiltration-hemodialysis, hemofiltration, or any combination of these with either acetate or bicarbonate based dialysate. Continued studies will be necessary to establish its full suitability for general use. However, we feel that the investigations of the various modes of dialysis therapy that this device makes so readily available show great potential for improving the treatment of ESRD.