Autonomic function in hemodialyzed patients

The authors have studied the autonomic function in a group of 34 regular hemodialyzed patients and in a group of 24 normal volunteers with simple, non-invasive and repeteable techniques. To evaluate autonomic function Valsalva manoeuvre, cold pressor test, mental stress test, tilt test, diving reflex test, systolic-time intervals and plasma catecholamines levels were used in all subjects. Uremic patients on maintenance hemodialysis were studied the day after hemodialysis. The response to cold pressor test, mental stress test, tilt test and plasma catecholamines levels resulted normal in all uremic patients, even if 17 out of 34 patients showed an abnormal response to the Valsalva manoeuvre (Valsalva ratio lesser than 1.40). In these patients an alteration of diving reflex and/or a pathological systolic-time interval was found. The authors suggest that sympathetic function is normal in regular hemodialyzed patients and that the abnormal response to the Valsalva manoeuvre is probably due to a defect in the vagal control of the heart and/or an alteration of cardiac performance.