Cutaneous vasomotor sensitivity to noradrenalin in spinal and intact man

It has been suggested that the increased pressor response to noradrenalin found in tetraplegic patients is due to absence of blood pressure restraining reflexes. However, it has also been found that below the lesion in such patients cutaneous vessels, which in intact man are not under baroreflex control, show prolonged vasoconstriction after sympathetic neural discharges. This finding might indicate that cutaneous blood vessels display an increased sensitivity to noradrenalin in spinal patients. To investigate this, photoelectric cutaneous pulse plethysmograms were monitored during i.v. noradrenalin infusions in six patients with spinal cord injuries and in six intact subjects. There were no significant differences between the groups in either extent or duration of vasoconstriction. The findings provide no evidence that increased sensitivity to noradrenalin is a factor of importance for the attacks of hypertension in tetraplegic patients.