Transcutaneous near-infrared spectroscopy for detection of regional spinal ischemia during intercostal artery ligation: preliminary experimental results.
OBJECTIVE
Real-time information about regional spinal cord ischemia can guide intraoperative management and reduce the risk of paraplegia after thoracic aortic surgery. We hypothesized that near-infrared spectroscopy could provide such information during intercostal and lumbar artery ligation in pigs.


METHODS
Transcutaneous near-infrared spectroscopic sensors were placed in the midline over the upper and lower thoracic vertebrae of 4 progressively larger pigs (weight range 21-70 kg). After the entire aorta was exposed, segmental arteries from T6 through L1 were sequentially ligated while regional oxygen saturation was monitored. Decreases in regional oxygen saturation were calculated as percentage changes from baseline. The degrees of ischemia in the upper and lower spinal cord were compared histopathologically.


RESULTS
Baseline regional oxygen saturations were similar in the upper (68.8% +/- 9.0%) and lower (68.0% +/- 11.5%, P = .82) cord. After ligation, however, regional oxygen saturation levels were significantly lower in the lower cord (41.3% +/- 10.1%) than in the upper cord (64.8% +/- 9.3%, P = .037). The regional oxygen saturation had decreased by 39.0% +/- 11.5% in the lower cord but only by 6.3% +/- 7.6% in the upper cord (P = .026). This difference was confirmed microscopically: upper-cord sections had fewer ischemic neurons (8.8 +/- 9.4) than did lower-cord sections (21.3 +/- 13.6, P = .002).


CONCLUSIONS
Intraoperative spinal cord ischemia was detectable with near-infrared spectroscopy in pigs weighing as much as 70 kg. The potential utility of this technique in patients undergoing thoracic aortic surgery warrants investigation.
LeMaire
Scott A
SA
Cardiovascular Surgery Service, Texas Heart Institute at St Luke's Episcopal Hospital, Houston, Tex, USA. slemaire@bcm.tmc.edu
Ochoa
Lyssa N
LN
Conklin
Lori D
LD
Widman
Ron A
RA
Clubb
Fred J
FJ
Undar
Akif
A
Schmittling
Zachary C
ZC
Wang
Xing Li
XL
Fraser
Charles D
CD
Coselli
Joseph S
JS
D000818:Animals; D001013:Aorta, Thoracic / Q000601:surgery*; D004195:Disease Models, Animal; D006454:Hemoglobins / Q000032:analysis; D007511:Ischemia / Q000175:diagnosis* / Q000209:etiology; D008026:Ligation / Q000009:adverse effects; D008161:Lumbosacral Region / Q000098:blood supply; D016343:Monitoring, Intraoperative; D010100:Oxygen / Q000032:analysis; D010108:Oxyhemoglobins / Q000032:analysis; D010865:Pilot Projects; D019265:Spectroscopy, Near-Infrared; D013116:Spinal Cord / Q000098:blood supply* / Q000473:pathology; D013552:Swine; D013909:Thorax / Q000098:blood supply
D006454:Hemoglobins; D010108:Oxyhemoglobins; C100003:deoxyhemoglobin; D010100:Oxygen