Diminished spinal cord perfusion despite distal aortic perfusion: an acute translational large animal experiment with occluded segmental arteries.

Objectives: Neuroprotective measures have been established in open thoraco-abdominal aortic aneurysm repair to reduce the incidence of postoperative paraplegia. Distal aortic perfusion (DaP) is meant to increase blood flow to the abdominal organs and the spinal cord. Cerebrospinal fluid (CSF) drainage is part of peri- and postoperative clinical routine. We aimed to investigate the effect of both techniques on spinal cord perfusion in an acute large animal model with segmental artery occlusion.

Methods: Eight pigs underwent minimally invasive segmental artery coil embolization prior to establishment of cardiopulmonary bypass with DaP. After initiation of DaP, CSF pressure was increased 3-fold by infusion of blood plasma. Collateral network near-infrared spectroscopy was used as an additional real-time monitoring method for indirect perfusion monitoring. Microspheres were injected for post-mortem regional spinal cord blood flow analysis.

Results: DaP led to an increase in spinal cord perfusion limited to the very lower spinal cord (L3-S, up to 400% of baseline) and the corresponding paraspinous muscle area. The most vulnerable region between T8 and L2 was not reached by DaP (between 14% and 46% of baseline). After initiation of DaP, a 10% increase in oxygenation via collateral network near-infrared spectroscopy was observed for the low lumbar region. The increase in CSF pressure counteracted enhanced perfusion inflow leading to a decrease in net tissue perfusion.

Conclusions: DaP is effective in increasing blood flow to the distal spinal cord (effectively counteracting CSF pressure increase) and paraspinous muscles, despite occluded segmental arteries, resulting in hyperperfusion potentially leading to spinal cord oedema and delayed paraplegia postoperatively.