Blood Trauma in Plastic Haemodialysis Cannulae

To investigate the haemolysis in haemodialysis cannulae, an in-vitro set up is built, using a unipuncture dialysis system. This system is connected to a bag with fresh calf's blood, by the cannula under test, mounted in a large bloodline (5mm diameter). The blood characteristics are kept constant by means of a bicarbonate dialysate in the dialyser. During a 6h period, haematological parameters are regularly sampled. Flow through the cannulae is recorded, which is about 500mUmin. Four different cannulae are tested and compared to the results obtained without any cannula in the circuit. In all cases a linear increase in plasma free haemoglobin levels is found after 6h. The cannulae can be ranked from 8F catheter over 13G, 14G to 16G cannula, the latter producing the highest degree of haemolysis. When using plastic cannulae at high blood flows, their haemolytic effect may not be neglected.