Safety and biological aspects of present techniques of haemodialysis

Haemodialysis (HD) is actually a procedure in which blood from the affected individual is lead via a tube system into a dialysis device in a extracorporeal circuit. This particular circuit has semipermeable membranes (dialyzer). Blood with uraemic toxins flows on one side, and a salt solution flows on the opposite side. The salt solution eliminates away waste material which have passed the membrane by diffusion or convection by means of small skin pores. From there the blood returns to the patient through a tubing system which has an air-trap and a sensor to prevent air contamination in the blood. Apart from air contamination, this procedure is overwhelmed with safety issues like biocompatibility, electrical safety and mechanical safety. The purpose of this dissertation was to look into the safety issues in haemodialysis devices concerning leakage current and air contamination during standard procedures and simulated fault conditions. Does the dialysis device constitute a risk for the patient?

To discover the extent of leakage current in HD machines, measurements at the filter-coupling site were carried out in vitro in accordance with the safety standard, IEC 601-1, in 5 forms of dialysis machines. To find out, in vitro, to what extent blood and priming fluid permitted leakage current to pass to the patient, leakage current were additionally assessed in the blood lines. The blood line was loaded with blood from donors or priming fluid in eight different runs. To discover if leakage current could impact biocompatibility, a Fresenius 2008C dialysis machine and 8 hemophan dialyzers were utilised. Blood lines contained about 400 ml heparinized blood from each of 8 different donors (in vitro). C3d was measured, in vitro, before start of a simulated dialysis and at 15, 30, 45 and 60 min. in the course of standard dialysis procedure….

Contents: Safety and biological aspects of present techniques of haemodialysis

INTRODUCTION
Uraemia
Dialysis
Need for renal replacement
The start of experimental dialysis treatment
Evolution during experimental treatments
Dialysis as an ordinary clinical treatment in 1960.
Interest from the industry
Priorities for treatment: a matter of life and deat
Dialysis today Active renal replacement today can be divided into three
principles:
Access techniques in extracorporeal dialysis or haemodialysis
Dialysis machine
The blood system
Fluid system
Blood distribution
Dialysis filter or dialyzer
Transport over the membrane
Diffusion principle
Ultrafiltration principle
Convection principle
Haemodialysis (HD)
Haemofiltration (HF)
Haemodialfiltration (HDF)
Safety in biomedical engineering, IEC 601
Fail life and fail safe
The frequency of electrical distribution
Physiological effects of electric current
Ventricular fibrillation
Cardiovascular collapse
Electrical safety in biomedical engineering
Table 1. Limits for leakage current in IEC 601
Overall safety issues for dialysis machines (IEC 601-2-16 )
Recommendations about acceptable levels of leakage currents and general standard vs. collateral standard for haemodialysis machines
Infusion of air
Figure 1. Risks of air infusion
Negative pressure
Residual air
Accidents and incidents, air/gas infusion
Infusion of air 601-2-16
Is there a safe level of air infusion?
Microinfusion of air or gas
Bubbles less than 40┬Ám in diameter
Bubble/blood interaction
Endothelial effects
Effects in capillaries
Effects in the lungs
Information and responsibility
AIMS
MATERIALS AND METHODS
Paper I, Dialysis machines
Electrical safety analyser, Rigel
Measurement of leakage currents
Accuracy of the Rigel safety analyser
Table 2. Estimated accuracy of a reading on the Rigel safety analyser
Paper II, Blood used
Priming solution and dialysis fluid
Electrical safety analyser
Dialysis system
Figure 2. In vitro measurement of leakage current
Statistics….

Source: Umea University

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