Preservation of spinal cord function after extensive segmental artery sacrifice: regional variations in perfusion

Sacrifice of intercostal and lumbar arteries simplifies thoracoabdominal aneurysm surgery and enables endovascular stenting. Little is known about alterations in cord perfusion after extensive segmental artery sacrifice. We explored this question using hypothermia to reduce metabolism.

Twelve juvenile Yorkshire pigs (mean weight, 22.3 kg) were randomized to segmental artery sacrifice at 32 degrees C or 37 degrees C. Cord integrity was assessed with myogenic-evoked potential (MEP) monitoring. Stepwise craniocaudal sacrifice of segmental arteries was continued until MEP diminution occurred; the last segmental artery was then reopened. Fluorescent microspheres were used to measure spinal cord blood flow (SCBF) at baseline, 5 minutes, 1 hour, and 3 hours after segmental artery sacrifice. Hind limb function was monitored for 5 days.

All animals recovered normal hind limb function. At 32 degrees C, more segmental arteries, 16.5 versus 15 (p = 0.03), could be sacrificed without MEP loss. Baseline SCBF at 32 degrees C was 50% that at 37 degrees C (p = 0.003) and remained fairly stable throughout. At 37 degrees C, SCBF to the craniocaudal extremes of the cord (C1 to T3 and L2 to L6) increased markedly (p = 0.01) at 1 hour and returned toward normal at 3 hours. Concomitantly, SCBF fell in the middle portion of the cord (T9 to T13) at 1 hour before returning to normal at 3 hours.

Almost all segmental arteries can be sacrificed with preservation of spinal cord function. No major change occurs in the central cord in normothermic animals, but there is significant transient hyperemia in segments adjacent to extrasegmental vessels. Hypothermia reduces SCBF and abolishes this possible steal phenomenon. Metabolic and hemodynamic manipulation should enable routine sacrifice of all segmental arteries without spinal cord injury.