Leukopenia and hypoxemia. Unrelated effects of hemodialysis.

Hemodialysis-induced hypoxemia has been attributed to membrane-related complement activation leading to pulmonary leukostasis and to hypoventilation secondary to carbon dioxide losses via the dialyzer. We have separately assessed the role of membrane- and dialysis-related factors by using different dialyzers and sequential ultrafiltration and hemodialysis with first-use cellulose dialyzers produced both leukopenia and hypoxemia. With reused cellulose and polyacrylonitrile dialyzers, hypoxemia still occurred, but without leukopenia. Ultrafiltration produced leukopenia and no changes in Pao2; during the subsequent hemodialysis, hypoxemia developed as the leukocyte count increased by 50%. Our data indicate that leukopenia and hypoxemia are unrelated effects of hemodialysis, and favor hypoventilation as the major determinant of hypoxemia during hemodialysis.

Two new concepts that might lead to a wearable artificial kidney.

A wearable artificial kidney involving two novel components is proposed. It consists of a turbulent flow ultrafiltering shunt, which supplies 20 liters of ultrafiltrate per day to a disposable activated charcoal cartridge (where creatinine, uric acid, and other tightly bound solutes are adsorbed) and then to an artificial loop of Henle (where the urea is concentrated into 2 liters of ultrafiltrate per day and discarded) from which 18 liters of cleansed, rewarmed ultrafiltrate containing 87% of the glucose is returned to the patient.

Combined technological-clinical approach to wearable dialysis.

To evaluate the constraints imposed upon the design of wearable dialysis systems, prototypes using currently available hardware were applied to three different dialysis formats: 1) the wearable artificial kidney (WAK) for hemodialysis (HD), 2) reciprocating peritoneal dialysis (RPD), and 3) alternating sorbent based dialysis/diafiltration(Ds/F) with a highflux membrane. 1) WAK dialysis has undergone extensive clinical trials with results comparable to standard HD. This system, including a self-contained power source, weighs 4.5 kg. The pulsatile blood flow can be disadvantageous, and cost of disposables is high. 2) RPD is shown to be an effective PD format, with the clearance of urea averaging 29.7 (23.9 to 41.5) ml/min in 14 patients, totalling 548 RPD dialyses. 3) After four conceptual trials, the Ds/F system was used for one treatment. Mass transfer results show removal of: urea nitrogen, 15.4 g; creatinine, 1.9 g; uric acid, 1.2 g; potassium, 89.2 mEq; and a positive bicarbonate balance of 94 mEq. The design constraints of these systems were elucidated, and prototype compact delivery systems have been constructed. It is concluded that a) non-mechanical PD wearability exists and b) true wearability of HD or Ds/F systems is not yet technologically feasible, but constraints are less rigid for Ds/F than for HD.

Dialysate delivery: historical, theoretical, and practical aspect.

Maintenance hemodialysis has progressed from a tentative therapy for a few patients in Seattle to a generally available treatment sustaining 100,000 patients around the world. The technical principles of dialysis are sufficiently understood to permit fabrication of disposable dialyzers in sheet, coil, or hollow-fiber configuration. Dialysate delivery systems can serve either single patients or groups of patients with high efficiency. Reduction in size of single-parent systems by incorporation of dialysate regeneration or miniaturization of components in a suitcase will promote patient mobility.

Effects of ultrafiltration on solute clearances in parallel plate dialyzers.

Clearances of small and large solutes were measured at increasing transmembrane pressure in 3 types of parallel plate dialyzers. Both laboratory and clinical studies were performed. As in previously reported studies in coils, diffusive transport appears to decrease as transmembrane pressure increases. This may reflect blood channel widening, bath channeling, and/or membrane masking by mesh support. For small solutes, decreases in diffusive transport were enough to offset gains by solvent drag and total clearances decreased. In some studies, decreases in small solute clearances with increasing ultrafiltration were large enough to compromise dialysis efficiency.

Clinical evaluation of an automated cleaning device for dialyzers.

This paper describes the clinical evaluation of dialyzer efficiency after cleaning and sterilization using an automated dialyzer cleaner. In vivo clearance measurements of small molecules and an in vitro measurement of BSP showed no diminution after 5 uses, and ultrafiltration rate did not decrease with an increase in dialyzer use. Scanning and transmission electron microscopy of the membrane showed an increase in accumulation of cellular debris and fibrin with increasing use. Our experience using the automated dialyzer clearner for more than one year leads us to conclude that it is an effective way to clean dialyzers and that no patient ill-health occurs as a result of re-using dialyzers cleaned by this technique.

Design analyses of a new selective filtration system for removal of uremic toxins.

A new system for removal of uremic toxins is described, The system is based on selective removal of small (urea, creatinine) and large uremic toxins through a multimembrane filter/dialyzer unit. Theoretical calculations show that the system is capable of removing the desired range of molecules from uremic plasma, while retaining a large portion of non-toxic elements in the blood. The SElective DUal Filtration ARtificial Kidney can be optimized and assembled into a single compact unit, which is simple to use and requires minimal monitoring equipment. Preliminary clinical trials indicate that SEDUFARK is a feasible system for treatment of uremic patients.

Short dialysis with a polyacrylonitrilmembrane (RP 6) without the use of a closed recirculating dialyzate delivery system.

Because of excessive eltrafiltration (UF), the RP 6 dialyzer requires a closed recirculating dialyzate delivery system. The purpose of this study is to present the characteristics of the RP 6 dialyzer on a single needle system which programs the UF rate of this dialyzer. The single needle system consists of one blood pu-mp and two roller pump heads, switched on and off at preselected maximum and minimum out let pressures (OP). It is possible to decrease the UF rate by lowering the OP in the bubble trap chamber. By varying OP from 0 to 100 mm Hg, we obtained an UF rate in vitro of 6.5 ml per minute. The clearance values, in ml/min, obtained at OP 0 to -100 NN Hg, QB 300 and QD 500 are (in ml/min): urea: 160.0, creatinine: 145.0, sucrose-C14: 105.4, sodiumiothalamate-i125: 79.9, cyanocobalamin-co58: 73.7 and inulin-3H: 40.7. The priming volume (corn-oil) at OP 0 to -100 MM Hg, QB 250, QD 500 varies between 140 ml (at the minimum OP) and 150 ml (at the maximum OP). We performed 370 dialyses. The dialysis runs were well tolerated: moderate hypotension occurred in 4% and cramps in 1.6% of the dialyses. In most cases no fluid perfusion was necessary. The residual blood volume (Technetium99m) is estimated at 8.2 ml(n equale 11).

Experience with a low volume ultrafiltration cell in small children*.

A low volume (16 ml) ultrafiltration cell was used ten times in two small, fluid overloaded children to remove plasma water. The device was simple to use and, at slow blood flow rates (25-50 ml/minutes) and low transmembrane pressures (10-30 mm Hg), provided controlled removal of excess fluid. Although no major complications were encountered, hypothermia and hypotension (at ultrafiltrate flux rates exceeding 0.5 ml/kg/minute) were observed. The ultrafiltrate solute concentration was similar to plasma and no significant shifts in serum electrolytes were induced. The ultrafiltrate protein concentration of 64 to 2,760 mg/dl was much higher than previously reported.

An automated cleaning device for dialyzers: machine design and technology.

The expansion of dialysis services and the introduction of disposable dialyzers have led to an increase in cost of hemodialysis. Many centers have attempted to reduce the cost of dialysis by using dialyzers on multiple occasions after cleaning and sterilization. Manual techniques for cleaning dialyzers are tedious, using valuable technician time and possibly leading to an increase in exposure to Hepatitis B surface antigen. These disadvantages can be avoided by the use of the automated device in this paper. We have also evaluated the dependability of the machine and the reduction in dialysis costs realized from its use.

A microcomputer based portable hemodialysis system.

A microprocessor controlled portable hemodialysis system (The Suitcase Kidney) has been designed and 18 dialyses have been successfully completed. The microprocessor is shown to be an improvement and simplification over the conventional discrete control mechanisms presently used to monitor and control system functions. The microprocessor is shown to reduce development time, complexity and size of the system while improving patient safety. A description of the system is presented emphasizing the functioning of the microcomputer.

Amberlite hemoperfusion in the treatment of acute drug intoxication.

Hemoperfusion is more effective than hemodialysis in clearing drugs from the blood of patients with acute overdose. In addition, the clinical improvement in the depth of coma is dramatic during hemoperfusion. There is normalization of the respiratory and circulatory systems usually within one hour, and response to verbal command within a few hours of initiating treatment. Amberlite XAD-4 is an unchanged polystyrene resin with a particular adsorptive attraction for lipid-soluble drugs. It is a more effective adsorbent than some of the coated or uncoated carbons in clearing blood of most of the drugs commonly involved in life-threatening acute overdose.

Electrical safety in dialysis.

Electrical hazards in dialysis equipment arise from the unintended passage of electric current through the patient. The main primary electrical hazards are described, and typical thresholds quoted. The complete dialysis installation is considered in some detail, bearing in mind the recently published British Standard on the Safety of Electromedical Equipment, BS 5724, Part 1. The microshock risk from leakage and fault currents flowing through the patient via the dialyser and lines is assessed and found to be of very little significance. Equipment that has been constructed to BS 5724 should not, by its design, give rise to primary electrical hazards. The continuing safety of dialysis installations can, however, only be ensured by regular routine testing, and suitable tests are described. It is concluded that, with regularly maintained and tested equipment, dialysis should be considered a relatively safe procedure as far as primary electrical hazards are concerned.

Renal dialysis membrane leak detector.

A leak developing in the membrane separating the blood from the dialysate in an artificial kidney machine requires immediate corrective action. The earliest possible action is desirable in order to minimize patient blood loss. This makes system sensitivity to hemoglobin concentration an important design criteria for blood leak detectors. The leak detector described in this paper matches the spectral properties of hemoglobin to those of the detector in order to achieve a maximum sensitivity while minimizing false alarms. The paper describes the instrumentation and circuitry as well as test results of simulated and clinical trials of the detection system.