Common carotid and common femoral arterial dynamics during head-up tilt in persons with spinal cord injury.

We examined the effect of the level and completeness of spinal cord injury (SCI), tetraplegia and paraplegia, on common carotid arterial (CCA) and common femoral arterial (CFA) functions supine and during head-up tilt (HUT), compared with able-bodied controls. Subjects (tetraplegia [n = 7], paraplegia [n = 8], and controls [n = 8]) were healthy males between the ages of 19 and 60 years. We used Doppler ultrasound to determine vessel diastolic diameters and flow velocities while supine and at 45 HUT. The results indicated that supine CCA diameter and flow were augmented in the tetraplegia group compared with the paraplegia group (p < 0.05); no other group differences were noted. However, CCA(flow) was significantly reduced from supine to 45 HUT in the tetraplegia group (p < 0.01). CFA diameter and flow were significantly reduced in the SCI groups compared with the control group, and CFA(flow) was reduced from supine to 45 HUT in the tetraplegia group. These results demonstrate that individuals with tetraplegia have increased resting CCA diameters and flows compared with individuals with paraplegia, an adaptation which may contribute to orthostatic tolerance. The significant reduction in CFA(flow) from supine to 45 HUT in the tetraplegia group may be related to the completeness of lesion rather than the level of lesion.