Enhanced pressor response to noradrenaline in patients with cervical spinal cord transection

Arterial blood pressure, heart-rate and the electrocardiogram were recorded in subjects tetraplegic from cervical spinal cord transections, and in control subjects, before, during and after intravenous infusions of 1-noradrenaline. Over a wide range of doses the blood pressure rose much more in the tetraplegics than in the controls. Circulating noradrenaline during infusion did not significantly differ between the two groups. The findings indicate that tetraplegic subjects have an enhanced pressor response to noradrenaline infusions. Such a response therefore does not necessarily indicate post-ganglionic sympathetic denervation. The observed responses in the tetraplegics may in part be due to exaggerated adrenergic receptor responses, but the main cause is likely to be the loss of those baroreceptor reflexes with sympathetic efferent pathways.