Clinical significance of bradykinin liberation during cardiopulmonary bypass and its prevention by a kallikrein inhibitor.

Activation of the kinin system and effects of Trasylol (Bayer, A.G. Lebukusen, West Germany), a kallikrein inhibitor, were investigated on 52 patients during hemodilutional cardiopulmonary bypass (CPB). Immediately after the start of CPB, neither elevation of bradykinin nor reduction of plasma kininogen (KGN: a precursor of bradykinin) were observed. During CPB, bradykinin level in the blood was markedly elevated, correlating with the significant decrease of kininogen (p less than 0.001). The longer the CPB time, the more marked the reduction of KGN. In the cases requiring over 60 minutes of CPB, the amounts of bradykinin released (4.6-18.0ng/ml) were sufficient to increase capillary permeability as well as peripheral vasodilatation. As shown by the sufnificant increase of hematocrit (p less than 0.005) and the extreme reduction of vascular resistance found at the end of CPB in the prolonged cases. Infusion of Trasylol into the extracorporeal circuit actually prevented the reduction of kininogen and the increase of hematocrit as well as the extreme decrease of vascular resistance in the cases of over 60 minutes CPB. These results clearly point out that Trasylol is beneficial for the prevention of bradykinin liberation and capillary permeability increase and for the maintenance of optimum peripheral vascular tone during CPB. Furthermore, the significance of these findings with regards to complications during and after prolonged CPB was discussed.