Abstract
We have performed a clinical study to analyse the cause of postoperative hypoxemia in patients who underwent upper abdominal surgery under general anesthesia by measuring A-aDO2 and a-ADN2 before and after operation. It is regarded that a-ADN2 is a most reliable index of unequal distribution of ventilation-perfusion rations in the lung. And the effect of pain relief by epidural injections of 2 mg morphine upon arterial blood gas and pulmonary function (spirometry, flow volume curve and single-breath nitrogen test) was examined after upper abdominal surgery.
PaO2 decreased and at the same time A-aDO2 and a-ADN2 increased on postoperative days. These changes were more remarkable in the aged patients. We presumed that the unequal distribution of ventilation-per-fusion rations in the lung played a role in the fall of postoperative PaO2, considering that both A-aDO2 and a-ADN2 increased in parallel after operation.
We have succeeded in reducing the postoperative hypoxemia by epidural injections of morphine. It is thought that this phenomenon is due to preventing FRC to decrease on postoperative days by pain relief.
