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

Background: Postprandial hypotension (PPH) appears in various conditions with autonomic failure and was symptomatic in a patient with thoracic paraplegia, but was not remarkable in patients with tetraplegia.

Objective: To determine whether the pathology causing PPH may include a thoracic but not a cervical spinal cord lesion (SCL).

Design: An experimental controlled study.

Setting: The spinal research laboratory, Loewenstein Hospital, Raanana, Israel.

Subjects: Thirteen healthy subjects, 10 patients with traumatic T(4)-T(6) paraplegia, and 11 patients with traumatic C(4)-C(7) tetraplegia.

Main Outcome Measures: Heart rate (HR), blood pressure (BP), HR and BP spectral components (LF, HF, LF/HF), cerebral blood flow velocity (CBFV), and cerebrovascular resistance index (CVRi).

Methods: The effects of a standard liquid meal on the outcome measures were compared between the three subject groups monitored for HR, BP, and CBFV, from 55 min before to 45 min after the start of the meal. The recorded signals were digitized online and analyzed off-line in the time and frequency domains.

Results: After meal, BP decreased only in the paraplegia group (P<0.01), HR increased more prominently in this group (P<0.01), CVRi tended to decrease only in the paraplegia group, CBFV did not change significantly in any group, and HR LF/HF increased (P<0.001) in all groups but tended to increase more in paraplegia.

Conclusions: Patients with mid-thoracic SCL may develop PPH. The pathology causing PPH can include a thoracic but not a cervical SCL. The normal hemodynamic reaction to liquid meal ingestion is mediated through the mid-thoracic spinal cord. The sympathovagal balance increases after food ingestion, more prominently in patients with PPH, and cerebrovascular resistance changes during PPH may help maintain the cerebral circulation.