[Plasma renin activity, plasma aldosterone and electrolyte balance in the postoperative period (author's transl)]

Plasma renin-activity and plasma aldosterone were measured by radioimmunoassay in 15 female patients before and 16 hours after intraabdominal surgery. Plasma renin was increased in all patients and plasma aldosterone in 12 patients after operation. Plasma renin and plasma aldosterone were correlated significantly (r=0.66, p less than 0.01) in the whole group. The increase of renin and plasma aldosterone was correlated inversely to urinary sodium-potassium-ratio. In 5 patients the increase of plasma renin and plasma aldosterone could not be prevented by the intra- and postoperative administration of 360 mEq of sodium, which was consequently retained. It is proposed that postoperative hyperaldosteronism is at least partly mediated through the renin-angiotensin-system. An absolute or relative sodium deficit appears to be an unlikely explanation for the stimulation of the renin-angiotensin-system in the postoperative period. The postoperative increase of plasma renin and consequently plasma aldosterone is possibly a consequence of anaesthetic induced impaired kidney perfusion and/or catecholamine mediated stimulation of renin release.