Cardiovascular and vasoactive hormone responses to bladder distension in spinal and normal man

Many patients with high spinal cord injury experience exaggerated blood pressure rises in response to bladder distension. To examine the humoral mechanisms associated with these responses, ECG heart rate, blood pressure and vasoactive hormone levels were measured at baseline and during bladder distension following slow bladder filling in 23 subjects: 9 high spinal lesion patients, 7 low spinal lesion patients and 7 normal control subjects. Systolic blood pressure rose significantly during bladder distension in the high spinal lesion group by an average of 56 mm Hg (48%) and diastolic blood pressure rose by 22 mm Hg (47%), while heart rate fell by a mean of 7.4 beats per minute (15%). By contrast, neither systolic or diastolic blood pressure nor heart rate changed significantly during bladder distension in the low spinal lesion or normal control group. There were no significant changes in plasma levels of noradrenaline, renin, aldosterone, vasopressin, arginine, or atrial natriuretic peptide during bladder distension to account for the blood pressure rise in the high spinal lesion group. These findings suggest that humoral mechanisms are unlikely to play a major role in the mediation of pressor responses to bladder distension in high spinal lesion patients.