Towards a diagnostic test of abdominal sympathetic dysfunction

Abstract

Extrinsic denervation of the gastrointestinal tract is associated with motility disorders; there is no simple, noninvasive, accurate method to evaluate abdominal sympathetic innervation. Thus, circulating catecholamines and cardiovascular reflexes do not accurately reflect abdominal sympathetic function (GE 1994; 106:1124-8). Our aim was to evaluate the role of superior mesenteric artery (SMA) blood flow in the pathophysiology of orthostatic hypotension (OH) in patients with generalized autonomic failure as a means to develop a test of abdominal sympathetic adrenergic function. Methods: 12 patients (5M, 7F; mean age, 60 years) with symptomatic neurogenic OH (6 multiple system atrophy, 3 pure autonomic failure, 3 diabetic neuropathy) and 12 healthy controls (5M, 7F; mean age, 43 years) underwent SMA flow measurements during cold pressor test, head-up tilt, and tilt plus meal ingestion. SMA flow was measured by a color Doppler ultrasonography scanner with a 3.75 MHz phased array sector transducer. Autonomic failure was independently assessed using standard tests of function of the sympathetic adrenergic, cardiovagal and postganglionic sympathetic sudomotor function. Results: SMA flow volume and time-averaged velocity were similar in patients and controls at rest in the supine position; however, responses to cold pressor test and uptight tilt were attenuated (p < 0.05) in patients compared to controls. Head-up tilt after the meal evoked a profound fall of mean blood pressure (84 12mmHg in controls, 54 ± 13 in patients; p < 0.05) and SMA flow in the patients.