Diminished vascular reactivity to a cold stress in azotemic patients

The integrity of the neurovascular reflex arc to a cold stimulus was evaluated by the determination of the response of the limb blood flow in fifteen azotemic patients. Seven of these patients became hypotensive during the course of renal failure despite comparable hemodialysis therapy. They showed a constant low blood pressure (mean blood pressure below 90 mmHg). The reactivity index (defined as the relative change at the 15th second of stimulus) was 15.9 +/- 14.4% for these hypotensive patients, and 35.7 +/- 12.0% for the remaining eight normotensive ones, while that of healthy subjects was 48.7 +/- 8.7%. The greatly diminished reactivity of the hypotensive patients could not be explained by humoral or hormonal factors. The dysfunction of somatic nerves of the vascular geometry could not be responsible for the difference. A dysfunction of adrenergic control of blood pressure was, therefore, strongly suggested.