Renin-aldosterone system and atrial natriuretic peptide during anesthesia in orthopedic patients over 80 years of age

Abstract

Study Objectives: To investigate the changes in plasma atrial natriuretic peptide, renin activity, and aldosterone during isoflurane anesthesia in patients over 80 years.Design: Prospective, randomized, controlled study.Setting: Operating rooms and postanesthesia recovery room of Hirosaki University Hospital and Hakodate Watanabe Hospital.Patients: 36 patients undergoing reduction of femur neck fracture (18 patients ranging in age from 80 to 99 years and 18 patients ranging in age from 40 to 59 years as control).Intervention: In all patients, anesthesia was induced with intravenous (IV) thiopental sodium 3 to 5 mg/kg succinylcholine 0.5 to 1.0 mg/kg for facilitating tracheal intubation and was maintained with 1.2% to 2.0% isoflurane in 50% oxygen.Measurements and Main Results: Plasma atrial natriuretic peptide (ANP), plasma renin activity (PRA), and plasma aldosterone (PA) levels were assayed. Blood samples were obtained on the following occasions: before the induction of anesthesia, 15 minutes after skin incision, 90 minutes after anesthesia induction, and the 60 minutes after the end of surgery. Plasma renin activity and PA levels in patients from 40 to 59 years increased significantly 90 minutes after induction, whereas PRA and PA levels in patients over 80 years were unchanged. There were significant differences in PRA and PA levels between both groups at any time of measurements. Plasma ANP levels of patients over 80 years were significantly elevated at 90 minutes induction. Plasma ANP levels in patients over 80 years at 90 minutes after the induction and 60 minutes after the end of surgery were significantly higher than those of patients from 40 to 59 years. Plasma renin activity in hypertensive patients over 80 years at 90 minutes after the induction was significantly lower than that observed in normotensive patients. The renal loss of sodium was increased in the hypertensive patients.Conclusions: Orthopedic patients over 80 years of age have decreased PRA and PA, increased ANP, and renal loss of sodium as compared with patients 40 to 59 years, during isoflurane anesthesia. Plasma renin activity at 90 minutes after induction was decreased in hypertensive patients over 80 years, but PA and ANP were not affected by hypertension during anesthesia.