The International Journal of Artificial Organs

New cuprophan dialysers were used in twenty, re-used dialysers in twelve dialyses and new dialysers in ten sequential ultrafiltrations. Serum beta 2-microglobulin (β2m) concentration was measured before and after all these procedures. Serum osmolality changes were compared with changes in serum β2m concentrations. These concentrations rose in dialyses with new and re-used dialysers, but remained unchanged during sequential ultrafiltration. β2m increased with serum hypo-osmolality, decreased with serum hyperosmolality and did not change during iso-osmolar dialysis. These results indicate that cuprophan membrane does not raise β2m concentration during dialysis. It is hypo-osmolality that is responsible for the increment of β2m in serum.

We describe the long term use for haemodialysis of the PermCath (Quinton, Seattle, Washington) dual lumen, jugular venous catheter (DLJVC) in 21 patients who had no apparent alternative means of access. The nineteen patients maintained in this manner for periods of 30 to 600 days (mean 233.2) included 6 patients dialyzed for over 12 months. Blood flows exceeded 250 mls/min and recirculation rates averaged 5.9%. Infection and insufficiency due to thrombosis were the major problems. In 8 patients (38.1%) infection required DLJVC removal; in three the catheter was immediately replaced over a guidewire along the same track under antibiotic cover and infection has not recurred. Insufficiency occurred in 10 patients (47.6%) and was successfully managed with oral anticoagulants, local instillation of urokinase (4 cases), systemic streptokinase (2 cases) or by changing the DLJVC over a guidewire (2 cases). We believe that the DLJVC is the long term access method of choice for patients in whom conventional access cannot be constructed.

In order to clarify the influence of serum potassium, serum sodium and plasma angiotensin II concentrations on aldosterone release during hemodialysis (HD), six chronic hemodialysis patients were studied during HD with varying dialysate sodium concentrations and different buffers. Plasma aldosterone concentrations were higher during acetate than bicarbonate HD, during low sodium compared to high sodium HD, and were correlated inversely to serum sodium concentrations. The decline in plasma aldosterone concentrations during HD paralleled the decrease in serum potassium concentrations, and plasma aldosterone concentrations were correlated with serum potassium concentrations. In addition, plasma aldosterone and plasma angiotensin II concentrations were correlated significantly. It is proposed that serum potassium and the renin-angiotensin system are the main factors of aldosterone release during hemodialysis, while serum sodium per se seems to be of less importance. The dialysate buffer employed also plays a role in aldosterone regulation (via the renin-angiotensin system)

The bacterial and endotoxin levels of purified water and effluent dialysate were examined in a cross section of dialysis centers in the central United States. All samples were collected within a four-hour drive of the University of Louisville and were collected, processed and analyzed by our personnel, to eliminate variability in sample handling. A medium capable of higher bacteria recovery from aqueous environments than those ordinarily employed in clinical assays was used. Endotoxins were determined by a quantitative colorimetric assay.

By the more sensitive bacterial assay 53% of the centers had bacterial counts above the AAMI standard of 200 colony-forming units per ml (CFU/ml) for water and 35% of the centers had bacterial counts above the 2000 CFU/ml standard for dialysate in at least one sampling period. The samples showed 35% and 19% of water and dialysate above the standards, respectively. While there are no standards for endotoxin concentrations in water used to prepare dialysate, 2% of the centers had endotoxin levels in their water above five endotoxin units per ml (5 EU/ml = 1 ng/ml in our assay kit), the limit set by the AAMI standards for reprocessor water. Both bacterial and endotoxin levels tended to be elevated in dialysate, with the highest levels of endotoxin in dialysates posing an obvious potential risk when high-flux dialyzers are used.

We evaluated the quantitative peritoneal leucocyte response to antibiotic therapy in 25 CAPD patients with 57 episodes of bacterial peritonitis. Eighty-eight percent of the peritonitis episodes were initially treated with a first generation cephalosporin, but results of microbial sensitivity studies led to a change in the initial antibiotic regimen in 23 episodes. Overall, 47/57 (82%) episodes were cured by antibiotic therapy alone (responders), while 10/57 (18%) required removal of the peritoneal catheter as a curative procedure (nonresponder). Neither the duration of symptoms on initial presentation nor the status of being a nonresponder could be related to the baseline peritoneal leucocyte values, either the total (PLC) or polymorphonuclear counts (PMN). Since the baseline PLC and PMN showed a 500-fold variation, subsequent changes were expressed as a percent [PLC (%) and PMN-PLC (%)] of the baseline value. On day 3 of peritonitis, PLC (%) and PMN-PLC (%) were less in responders (26% and 10%) than nonresponders (251% and 254%) (p<0.001). Differentiation between responders and nonresponders based on PLC (%) and PMN-PLC (%) was associated with a high degreee of sensitivity (90%) and specificity (90%). Similar results were obtained for day 4. These data suggest that the temporal pattern of PLC and PMN, when expressed as a percentage of the baseline value, may be useful in predicting those episodes of peritonitis which require removal of the peritoneal catheter.

Right/left matching in the total artificial heart (TAH) is essential to prevent fatal volume displacement into the pulmonary circuit. Measurements were made with three different sized Rostock pneumatic artificial ventricles incorporated in the Donovan mock circulatory system together with the heart driver AKT 86. First for each ventricle we determined the dependence of the maximum effective stroke volume on the systolic driving pressure and the afterload. The right ventricle (RV) is about 10% more effective than the left ventricle (LV). Control of the TAH permits different or equal frequencies for the RV and LV. For control with equal frequencies and full-to-empty regimen of one ventricle (RV-Master or LV-Master) the ratio of designed stroke volumes between RV and LV is important. This follows from the smaller efficiency of the LV and the left-to-left shunt. Otherwise a control mode with different heart rates must be used.

Particle spallation and plasticiser (DEHP) release from medical grade polyvinylchloride (PVC), co-extruded PVC-polyurethane (PIVIPOL)^R and an experimentally produced co-extruded PVC-ethylene vinyl acetate (EVA) has been studied when used with manually occluded and self-occluding peristaltic pumps over a six hour pumping period. The shore hardness of the tubings studied were similar but the luminal coating thickness differed (0.2 mm polyurethane, 0.99 mm EVA).

The pattern of particle release was similar for all materials on the pump type used with the majority of particles released being less than 5 microns in diameter. The number of particles greater than 5 microns released was independent of the tubing material but depended on the pump type. Particle release with self-occluding pumps was significantly higher (p<0.001) than for the manually occluded pump. Scanning electron microscopy indicated that the particles released originate from the repeated compression and flexing of the insert during pumping which leads to material structural failure. The higher release observed in the case of self-occluding pumps is suggestive of over-occlusion by the springs utilised in the pump.

DEHP release (ppm) over a six hour period while perfused at 300 ml/min was significantly reduced for co-extruded tubing (0.56 ± 0.05 mg (PVC-polyurethane) and 0.12 ± 0.04 mg (PVC-EVA) compared with PVC (0.74 ± 0.05 mg).