体外循環における血液凝固に関する研究

Experimental and clinical study on blood coagulation during profound hypothermia either by surface cooling or by extracorporeal circulation was made and the effect of hemodilution in the extracorporeal circulation was investigated. The result was summarized as follows; 1) Profound hypothermia by surface cooling caused decrease in the platelet count and reduction of its function. The count recovered to normal level soon after rewarming but the functional insufficiency remained longer even after the rewarming. The profound hypothermia for less than one hour gave no significant influence on clotting factors other than the platelet. 2) After the extracorporeal circulation alone, decrease in platelet count and the damage on clotting factors were generally observed, but they were temporary and recovered within 24 hours in nearly all cases. However, when the extracorporeal perfusion was prolonged, the disturbance in the first and the second phase in clotting mechanism were remarkable and persistent to result in voluminous postoperative hemorrhage. Hence, it is quite desirable that the extracorporeal perfusion is terminated within 2 hours after the start. 3) Most of the patients with cyanotic congenital heart disease were accompanied by abnormalities in vascular resistance, count and function of platelet and factors relating to blood coagulation. It is of clinical importance that postoperative augmentation of these abnormalities was not rare. 4) The hemodilution with low molecular weight dextran, modified by the author, was applied for the extracorporeal circulation to obtain profound hypothermia. In this profound hypothermia, such abnormalities in clotting factors as manifest the bleeding tendency were not observed, though heparin rebound phenomena appeared in occasional cases. 5) In the extracorporeal circulation, the application of hemodilution with low molecular weight dextran solution by twenty per cent of the total priming and circulating blood volume was advantageous for prevention of occurrence of the abnormalities in clotting process which was caused by undiluted whole blood.