Persons with chronic primary autonomic failure and widespread sympathetic denervation and postural hypotension often have postprandial hypotension (Mathias, 1991).  Food consumption often exacerbates symptoms and the degree of postural hypotension in certain groups.  The cardiovascular responses to food ingestion in individuals with tetraplegia have not been investigated.

Table: Cardiovascular and Hormonal Responses to Food Ingestion

Discussion

A fall in blood pressure following the ingestion of food has been described in individuals with secondary autonomic failure of various causes; however, the cardiovascular and hormonal responses to food ingestion in individuals with tetraplegia with cervical spinal cord transection have not been studied.  Baliga et al. (1997) investigated the effects of a standard liquid meal (300 mL total liquid volume, 550 kilocalories, 66 grams carbohydrate, 22 grams fat, 18 grams protein) on blood pressure (BP), heart rate (HR) and neurohormonal levels in tetraplegics with physiologically complete cervical cord transection.  Five paraplegics with complete lesions (T12-L3) and essentially intact sympathetic nervous systems who did not experience postural hypotension served as the control group.  The experimental group consisted of 6 tetraplegics (C4 – 7) with chronic and complete cervical spinal cord transection.  All had postural hypotension.  After food ingestion there was no fall in BP in tetraplegics or controls.  HR did not change in either group.  Following food ingestion plasma noradrenaline was unchanged in tetraplegics but rose in controls.  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 the pre-prandial tilt in either group; post-prandial tilt raised levels in the tetraplegics but not in the controls.  The authors summarized that there is a difference in the responses to food ingestion between tetraplegics and paraplegic controls and even more pronounced differences from other autonomic disorders with sympathetic dysfunction which may relate to the site and nature of the sympathetic lesion and compensatory mechanisms.   

Conclusion

• There is level 3 evidence from one case control study (Baliga et al., 1997) that consumption of a standard liquid meal does not change blood pressure, heart rate or noradrenalin levels in tetraplegics with postural hypotension. 

• Consumption of a standard liquid meal does not change blood pressure, heart rate or noradrenalin levels in tetraplegics with postural hypotension.