On the local heparinization of the artificial heart pump

Abstract

We are now engaged in a chronic left heart bypass experiment using an artificial assist heart on calves, but as of this date there has not yet been developed a completely non-thrombogenic material for use in the artificial heart pump. It is for this reason that prevention of thrombogenesis has become an important problem especially when long survival following surgery is sought, and thus there is a need to conduct a proper anti-thrombogenic therapy through an appropriate method. We first attempted general heparinization by one-shot intravenous injection of heparin, but by this method it was invariably difficult to maintain the heparin level and generalized bleeding tendency was frequently observed.
In order to prevent the risk of bleeding due to this generalized heparinization and to remove the thrombogenic tendency during the acute stage within the artificial heart pump, it would be ideal to develop a method by which a non-clottable condition could be maintained only within the blood pump.
To achieve this purpose we considered that local heparinization in which heparinization could be localized within the blood pump and blood neutralized by protamine could be pumped throughout the body would be effective.
We thus attempted a method of neutralizing the heparinized blood by continuously injecting heparin in the inlet side of the blood pump and by continuously injecting protamine in the outlet side of the pump.
In Group A the heparin dose was 50U/kg/h and in Group B the dose was 25U/kg/h. The protamine dose was equivalent to the heparin dose in one half of Group A and Group B and in the remaining half of Group A and Group B, the protamine dose was one half of the heparin dose.
Furthermore, to determine the heparin level in the blood prothrombin time was determined over time, using prothrombin time as an index of heparin level.
In both Group A and Group B satisfactory anti-thrombogenic effect was observed, but in Group B hardly any bleeding tendency could be noted, whereas in Group A bleeding tendency was noted in some cases. On the basis of these results, we have administered on 16 cases to date heparin at a dose of 25U/kg/h and protamine at a dose range of 10-25U/kg/h as early as 12-24hours following surgery when oral administration becomes possible.
Prothrombin time can be controlled within the range of 1.5-2.0times that of the normal value and good anti-thrombogenic effect could be obtained, this range being sufficient to prevent bleeding tendency.