Spinal cord collateral flow during antegrade cerebral perfusion for aortic arch surgery

Objective: We aimed to monitor regional oxygen saturation levels using near-infrared spectroscopy in patients undergoing total aortic arch replacement and to determine the range of collateral flow via antegrade cerebral perfusion to the spinal cord during lower body circulatory arrest.

Methods: Eighteen consecutive patients undergoing total aortic arch replacement in our hospital were prospectively enrolled. Optodes of near-infrared spectroscopy were attached to the skin at the right and left forehead, and above the paravertebral muscles at the level of the third (T3) and tenth (T10) thoracic vertebra. Within- and between-group differences were compared using mixed-effect model repeated-measures analysis.

Results: Regional oxygen saturation levels, which had been rapidly declining immediately after circulatory arrest at a tympanic temperature of <25°C and a core temperature of <30°C, showed a rapid increase at the forehead with the initiation of antegrade cerebral perfusion (total flow rate 0.81 ± 0.08 L/min, perfusion pressure 37 ± 6 mm Hg, temperature 25°C). Saturation levels remained only partially elevated at the upper thoracic level (T3) and continued to decline without showing signs of recovery at the lower thoracic level (T10).

Conclusions: Antegrade cerebral perfusion partially perfused the upper thoracic cord via collateral circulation from vertebral arteries through an anterior spinal artery, but it did not reach the lower thoracic cord sufficiently to change the oxygenation level. Cooling is a more important means of protection for the lower spinal cord during lower body circulatory arrest than is antegrade cerebral perfusion.