Spinal cord blood flow and ischemic injury after experimental sacrifice of thoracic and abdominal segmental arteries

Objective: Spinal cord bloodflow (SCBF) after sacrifice of thoracoabdominal aortic segmental arteries (TAASA) during thoracoabdominal aortic aneurysm (TAAA) repair remains poorly understood. This study explored SCBF for 72 h after sacrifice of all TAASA. Methods: Fourteen juvenile Yorkshire pigs underwent complete serial TAASA sacrifice (T4—L5). Six control pigs underwent anesthesia and cooling to 32 8C with no TAASA sacrifice. In the experimental animals, spinal cord function was continuously monitored using motor evoked potentials (MEPs) until 1 h after clamping the last TAASA. Fluorescent microspheres enabled segmental measurement of SCBF along the entire spinal cord before, and 5 min, 1 h, 5 h,24 hand72 haftercompleteTAASAsacrifice.AmodifiedTarlovscorewasobtainedfor3daysaftersurgery.Results:Allthepigswithcomplete TAASA sacrifice retained normalcord function(MEP) until 1 h after TAASA ligation.Seven pigs(50%) with complete TAASA sacrifice recoveredafter 72 h; sevenpigs sufferedparaparesis orparaplegia.Intraoperatively, anduntil 1 h postoperatively, SCBFwassimilar amongthethreegroups along the entire cord. Postoperatively, SCBF did not decrease in any group, but significant hyperemia occurred at 5 h in controls and recovery animals, but did not occur in pigs that developed paraparesis or paraplegia in the T8—L2 segments (p = 0.0002) and L3—S segments (p = 0.0007). At 24 h, SCBF remained marginally lower from T8 caudally; at 72 h, SCBF was similar among all groups along the entire cord. SCBF in the segments T8—L2 at 5 h predicted functional recovery (p = 0.003). Conclusions: This study suggests that critical spinal cord ischemia after complete TAASA sacrifice does not occur immediately (intraoperatively), but is delayed 1—5 h or longer after clamping, and represents failure to mount a hyperemic response to rewarming and awakening. The short duration of low SCBF associated with spinal cord injury suggests that hemodynamic and metabolic manipulation lasting only 24—72 h may allow routine preservation of normal cord function despite sacrifice of all TAASA secondary to surgical or endovascular repair of large TAAA. # 2008 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.