特別発言(1) 酸素供給からみた離脱の条件

抄録

This review explains the physiological bases of oxygen transport and evaluation of the heart muscle contractility when we stop the assist circulation of the cardio-pulmonary bypass. When the cardiac index becomes more than two l/min/m² and the pressure of the left atrium becomes less than 18mmHg, we usually stop the assist circulation. And we also know Forrester's indication of the heart failure. However, there are controversies about the timing of the weaning from the assist circulation. We refereed the relationship of cardiac output and oxygen consumption which were obtained both at the resting condition and during mild to severe exercise. Then we interpolated the value of the minimum cardiac output to survive from the results. The value indicates 1.0l/min/m² in the cardiac index. The another limitation may be the maximum pressure of the left atrium to be proof against the lung damage. Forrester noted when the value becomes more than 18mmHg, the congestive lung will occur. But the actual lung can tolerate higher pressures, Judging from our analyois of pulmonary lymphatic drainage, 25mmHg of LAP within 30 minutes will never induce acute pulmonary edema.
In this article, I also introduce the QD and DS time during the cardiac surgery as the indices of the cardiac contractility. QD time is the duration time from R wave of ECG to the arterial end diastolic pressure. DS time is the duration time from the end diastolic pressure to the systolic pressure. When the duration of the DS time decrease less than 200 msec, the patients weaned from the cardio-pulmonary assist circulation. The evaluation of these indicator is not certain now, but the electrical circuit can measure these values easily and we can measure them continuously during and after the cardio-pulmonary bypass.