[Plasma renin activity and plasma aldosterone during anaesthesia and operative stress and beta-adrenergic blockade...

In 21 patients undergoing ear operations associated with minimal bleeding plasma renin activity and plasma aldosterone concentration were studied before and during surgical procedure, and in the postoperative state. Studies were performed in two groups, one without (n=9) and one with beta-adrenergic blockade by Practolol (n=12). Plasma renin activity increased significantly during halothane anaesthesia alone whereas the surgical manipulations did not further influence mean values significantly. Thus, it seems to be established that anaesthesia per se influences renin secretion. On the other hand Practolol does not show an inhibiting effect. The plasma renin increase following anaesthesia is due to the hemodynamic including renal hemodynamic, changes as well as to activation of the sympatho-adrenal system. Changes in plasma aldosterone are variable. For the greater part of patients with beta-adrenergic blockade an increase during the operative procedure was found. However, in some patients especially in the control group, plasma aldosterone was unchanged or decreased in spite of increasing renin values. Significantly lower plasma potassium concentration in these cases seems to indicate the important contributing role of potassium for the short-term regulation of aldosterone secretion. Plasma sodium concentration remained unchanged for the periods studied.