Blood damage is an unavoidable side effect of extracorporeal circulation. The effects of blood damage on patients' hematocrit and erythropoietin requirement as well as other potential side effects have not been studied for uneventful treatments. Comparing long nocturnal dialysis with regular 4-hour, three times per week dialysis allows for the conclusion that the influence of blood damage caused by extracorporeal circulation is small compared with biochemical effects. Acute hemolysis is one of the few remaining mechanical problems of dialysis. Acute hemolysis is caused by obstructions within the extracorporeal circuit caused by manufacturing errors, kinking of blood tubing or user errors, or by a combination of excessive flow and improper cannula or catheter dimensions. The risk of acute hemolysis can be further reduced by industrial quality control, better design of dialysis equipment, and hemodialysis machine control. Adverse effects caused by chronic mechanical hemolysis need to be studied.

Daily dialysis offers many benefits but is difficult to implement. CRRT allows dialysis 24/7 but is not suitable for ESRD patients. Thus, the need for a miniaturized ambulatory CRRT device those patients can wear permanently. We report the feasibility, safety and efficiency in uremic pigs, of such a wearable artificial kidney (WAK) that can be worn as a belt, operated with batteries, and weights less than 5 lbs. We used a hollow fiber dialyzer with a surface area of 0.2 sqm. Dialysate was continuously regenerated by a series of cartridges containing several sorbents allowing the use of approximately 375 ml of dialysate. The device includes reservoirs with heparin and electrolytes. Average fluid removal was 100 ml/hr. The Creatinine was 25 ml/min. In 8 hrs the total Creatinine removed was 1 gr, Urea 12 gr, P0.8 gr and K 72 mEq. Weekly st kt/v was extrapolated to approximately 7. There were no side effects. The WAK can be operated safely and continuously 168 hr/week. This would allow for all the advantages of daily dialysis and reduce morbidity and mortality in the ESRD population. It will also reduce cost and manpower utilization.

Avoidance of clotting in catheter lumens between treatments usually entails locking with an anticoagulant solution such as heparin. Catheter manufacturers specify internal volume of the catheters, and it is commonly assumed that injection of this precise filling volume is safe and efficient. However, it has been shown that activated partial thromboplastin time (aPTT) increases after instillation of the heparin lock volume specified by the manufacturer. We have investigated this phenomenon in vitro using dye and saline dilution and found that injection of the catheter volume results in spillage of up to 15% of the catheter volume into the patient's blood. Depending on fluid dynamics of the instillation process and catheter compliance, the concentration of the locking solution at the catheter tip is much reduced. As a consequence of this overshoot, the mean concentration at the tip is reduced to approximately 90%. In conclusion, the injection volume must exceed 120% of the catheter lumen for achieving the full strength of the locking solution at the tip. The overshoot may have clinical consequences, (e.g., bleeding if highly concentrated heparin is used).

The avoidance of clotting in catheter lumina between treatments usually entails locking with an anticoagulant solution such as heparin. In a previous work, it was shown that approximately 20% of locking solution flows from the catheter during instillation of the lock equal in volume to the lumen volume. Furthermore, the locking solution may spill into the blood stream under the influence of gravity. This work investigates the influence of density and viscosity of the locking solution on the volume and speed of locking solution loss from the catheter lumen. A large fraction of the catheter locking solution spills under the influence of gravity if the locking solution's density is higher than the fluid it spills to (blood). Locking solution lost is replaced by blood. Viscosity delays this process, but at 90 minutes after injection, the loss is completed even when highly viscous lock solutions are used. Slow administration of the lock has negligible influence upon the dynamics of the loss.

No abstract

No abstract

No abstract

A theory was developed allowing the prediction of the spillage volume after injection of locking solution into a catheter. This theory was corroborated by in-vitro measurements using colorized fluid injected automatically by a micropump into a stirred container with clear fluid. The amount of spilled solution was measured with a fiberoptic spectrometer equipped with a dip probe. Straight cylindrical tubing was used as catheter. Results: The theory predicts the beginning of spillage when 50% of the catheter filling volume is injected. When the nominal filling volume is injected, 25% of the solution is spilled and the mean concentration at the catheter tip is 50% of the locking solution concentration. Experiments: Spillage was slightly less than predicted (20–25% at nominal filling volume). During the experiments it was recognized that a small air bubble trapped in the Luer connection during connection reduces the spillage volume to 10–15%.