In vitro evaluation of heparin adsorption during haemoperfusion with Dowex 1 x 2 anion exchange resin

Haemoperfusion treatments have found clinical applications in various pathologies, even though problems due to the insufficient biocompatibility of sorbents have often limited its employment. Among these problems, there is that of heparin adsorption which can determine coagulation disorders or the necessity of a dosage correction during the extra corporeal circulation. The aim of the study was to test the influence of different methods of coating on heparin adsorption from an anion exchange resin coated with poly-hydroxyethyl-methacrylate. Eight haemoperfusion cartridges were prepared using 8 g of resin for each (4 cartridges contained resin coated by spray-coating technique and 4 coated by phase-separation one). Haemoperfusion was performed by using 600 IU of heparin (25,000 IU) corresponding to 0.12 ml in 500 ml of swine blood and a closed circuit. Blood flow rate was maintained at 15 ml/min and the circuit pressure was 70 torr during haemoperfusion. Blood samples were withdrawn at timed intervals before and after the column in order to evaluate blood heparin levels. The results demonstrated the superiority of the phase-separation technique that does not permit any interactions between adsorbent substance and drug. As a result of this, the adjustment of the dosage may not be necessary during further in vivo experiments.