Cardiovascular and hormonal responses to food ingestion in humans with spinal cord transection

Abstract

In sympathetic denervation due to primary autonomic failure, ingestion of food causes a fall in blood pressure (BP) and exacerbates postural hypotension. It is not known whether these responses occur in tetraplegics with physiologically complete cervical spinal cord transection, who also have sympathetic dysfunction because of disruption of descending spinal sympathetic pathways. We, therefore, studied the effect of a liquid meal on BP, heart rate (HR) and neurohormonal levels in tetraplegics. Paraplegics with low lesions and without sympathetic dysfunction served as controls. After food ingestion, there was no fall in BP in tetraplegics or in controls. HR did not change in either group. After fund, plasma noradrenaline was unchanged in tetraplegics, but rose in controls, while plasma renin activity (PRA) rose in tetraplegics but not in controls. The fall in BP and rise in HR on head-up tilt after the meal in tetraplegics was similar to that before the meal. There was no change in PRA following pre-prandial tilt in either group; post-prandial tilt raised levels in the tetraplegics, unlike in controls. Thus there is considerable variance in the responses to food between tetraplegics and paraplegic controls, and even greater differences when compared with published data in other autonomic disorders with sympathetic dysfunction; this may relate to the site and the nature of the sympathetic lesion and the ability to activate compensatory mechanisms.

Hemodynamic effects of liquid food ingestion in mid-thoracic paraplegia: is supine postprandial hypotension related to thoracic spinal cord damage?

“…1 However, this effect was probably negligible as renin half-life in the circulation is 15-30 min, 15 and plasma renin activity measurements (to be presented in detail elsewhere) were not significantly different in patients with tetraplegia at supine rest before the preceding tilt or 15 min after meal start. The negligibility of this effect is further supported by a previous study, 4 in which renin activity and pre-meal BP were not affected by HUT that ended 10 min before a similar meal.…”

“…1 Surprisingly, marked PPH could not be demonstrated in patients with severe cervical spinal cord lesions (SCL), in either the supine or tilted position, despite their obvious autonomic dysfunction. 1,4 However, PPH was demonstrated, in a single case report, after thoracic SCL with complete neurological deficit below the T 3 segment. In that case, the hypotension was symptomatic when food ingestion was followed by head-up tilting (HUT).…”

The prevalence and association of neck (coat-hanger) pain and orthostatic (postural) hypotension in human spinal cord injury

“…A similar study with food challenge demonstrated an abnormal hormonal response in SCI, resulting in no eect on the OH induced by head-up tilt. 19 Three subjects in our study reported that their pain improved when performing pressure sore prevention manoeuvres (leaning forward on the wheelchair with the head towards the knees) that are also expected to improve OH. Furthermore, a tetraplegic subject indicated that neck pain was triggered regularly when his ventilator was turned o to encourage active breathing; whether this suggested an in¯uence of blood oxygenation on his neck pain, as may be expected with diminished blood¯ow in the other subjects, can but be speculated upon.…”

Hemodynamic responses to head-up tilt after spinal cord injury support a role for the mid-thoracic spinal cord in cardiovascular regulation

“…Several publications show that cardiovascular impairments may be expressed differently in cervical and thoracic SCI, and that the autonomic deficit following thoracic SC lesions may have a specific clinical significance. [3][4][5] Responses to liquid food ingestion, cold application to the hand and cold application to the foot [6][7][8] indicated that the hemodynamic changes are mediated by a mid-thoracic SC mechanism. But data showing a role for the mid-thoracic SC in the control of hemodynamic changes in the upright position has been scarce.…”