[The effect of the perfusion parameters on the functional characteristics of the thrombocytes]

Platelet and plasma monoamine oxidase (MAO) activity was evaluated in two groups of patients at different stages of surgery (before perfusion, at the depth of cooling, height of warming, and 1 h and 24 h after perfusion). Group 1 consisted of 26 patients with acquired heart diseases operated on under artificial circulation and hypothermia (26-29 degrees C), group 2 consisted of 13 patients subjected to reconstructive operations on the aorta under artificial circulation with deep hypothermia (14 degrees C) and circulatory arrest for 50 min. The activity of platelet MAO was decreased in group 1 (by more than 50% during cooling and by 68% during warming and 1 h after perfusion); 24 h after surgery MAO activity increased, but did not reach the initial value. In group 2 the decrease in MAO activity was more expressed, starting from the second switching of the artificial bypass device after circulatory arrest (by almost 50% during cooling, by almost 90% after second switching of artificial circulation, by 94% during warming, and by at least 70% 1 h after perfusion); 24 h after the intervention the platelet MAO activity increased negligibly. MAO activity in the plasma notably increased in both groups during surgery, more so in group 2, which indicates washing out of the enzyme from platelets during artificial circulation because of these cells' damage. These data suggest that platelet injury is a result of their mechanical injury in the bypass circulation and of excessive partial oxygen pressure (400 mm Hg and higher) during perfusion, due to increased oxygen solubility in the plasma at low temperature. This leads to production of excessive active oxygen forms which damage cell membranes and inhibit MAO activity.