Additional Notes
It works on the basis of the diffusion of blood against a dialysate across a semipermeable membrane. The blood enters thousands of small semipermeable microtubules with dialysate fluid running in the opposite direction. Dialysate contains high bicarbonate to correct acidosis, low potassium and low calcium. High blood flow (200 ml/min) is needed so a surgically constructed AV fistula where there is a connection between arterial and venous blood is placed usually in the forearm. It usually feels like a cat purring under the skin. The endothelium of the venous side of the shunt becomes thickened and arterialised over 6 weeks and so can be used with the large needs required for dialysis. The patient is prepared for dialysis at CKD stage 4 allowing time for fistula development. Where there is no fistula then central venous access with a double lumen catheter either in the internal jugular or subclavian and lastly femoral vein. Haemodialysis can be carried out usually for 4-5 hours 3 times a week. Heparin is needed to ensure that clotting does not occur as the blood circulates through the haemodialysis. Hypotension is one of the commonest complications due to volume loss in the process. Patient weight is a guide. Remember also that dialysed patients are basically immunosuppressed and infections need treatment early. Creatinine and urea improve but not back to normal levels. The following drugs can be dialysed Alcohol, Barbiturates, Ethylene Glycol, Lithium, Methanol, Salicylate, Theophylline. Complications are Fluid overload, Hypotension, Atherosclerosis, Sepsis, Carpal tunnel syndrome (Beta2 microglobulin) not removed by haemodialysis and builds up over months and years.
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