Modified cold pressor test by cold application to the foot after spinal cord injury: suggestion of hemodynamic control by the spinal cord.

OBJECTIVE

Study hemodynamic responses to cold application to the foot (CAF) to explore the autonomic cardiovascular control by the spinal cord.

DESIGN

Controlled experimental study. Hemodynamic variables were measured or calculated for 13 healthy subjects, 10 patients with traumatic T4-T6 paraplegia, and 11 patients with traumatic C4-C7 tetraplegia. Subjects were continuously monitored for heart rate (HR), blood pressure (BP), and cerebral blood-flow velocity (CBFV) from 5 mins before to 5 mins after 40-120 secs of CAF by ice water foot immersion. The recorded signals were digitized online and analyzed offline in the time and frequency domains.

RESULTS

During CAF, HR increased in the control group but decreased in patients (P < 0.001). BP increased significantly in the control and tetraplegia groups (P < 0.001) and nonsignificantly in the paraplegia group. HR and BP spectral components (LF, HF, LF/HF) did not change significantly. CBFV increased significantly in the patient groups (P < 0.05) but not in the control subjects. The cerebrovascular resistance increased significantly in the control and tetraplegia groups (P < 0.001), but not in the paraplegia group.

CONCLUSIONS

The findings support the presence of hemodynamic autonomic control by the spinal cord and show that responses to CAF can be used to assess its integrity.