 heparin level hypotherm perfus 1 perfus-temperatur influenc rate heparin-loss extracorpor circul requir re-heparin 2 heparin half-live 13 4 hour 21 2 hour calcul perfus conduct averag temperatur 31 5 22 6 3 rate heparin-loss extracorpor circul inconst individu variabl individu exact neutral requir accur estim heparin concentr perfus 4 protamin titrat test crude simpl satisfactori monitor free-heparin level 5 complet neutral heparin factor minim postop blood loss 6 protamin effici neutral agent polybren dosag level effect divid dosag 7 rebound detect 5 45 case studi instanc degre 8 prolong clot-time excess neutral agent evid studi 