General anesthesia and surgical stress increase plasma immunoreactive beta-endorphin-like substances.

The concentrations of human immunoreactive beta-endorphin-like substances in plasma were measured as a means of determining the effects of general anesthesia and surgical stress on the endogenous morphine-like substances. Sixty-nine adult patients and 44 pediatric patients who had undergone oral surgery in general anesthesia were the subjects of this study. In comparison to the control values, the results of this study showed an increase of beta-endorphin concentration in the plasma during anesthesia and surgery. The increase was particularly significant in the patients who had relatively a major surgical stress and in those patients showing a weak anesthetic action, while the patients with relatively a minor surgical stress or strong anesthetic action showed a small increase. From these findings, it seems proper to assume that the secretion of beta-endorphin in the plasma is accelerated by general anesthesia and surgical stress than to assume that the amount of beta-endorphin in the plasma is increased by the administration of anesthetic agents.