Immediate Spinal Cord Collateral Blood Flow During Thoracic Aortic Procedures: The Role of Epidural Arcades

Abstract

The objective of this study was to investigate the functional differences between paraspinal and intraspinal compartments of the spinal collateral network and the importance of circular epidural arcades in thoracic aortic surgery. N = 33 pigs (mean body weight: 34 ± 3kg) were included. A single-inlet-model of spinal collateral flow was created: paraspinal inflow into the collateral network was isolated by cephalad and caudal interruption of inflow into epidural arcades using laminectomies. Animals were assigned to treatment groups (Treatment "open" [patent epidural arcades, n = 10] and Treatment "closed" [closed epidural arcades, n = 10]) and Sham groups (Sham "open" n = 8 and Sham "closed" n = 5). Treatment was a simulated Frozen Elephant Trunk procedure with occlusion of left subclavian and thoracic segmental arteries under mild permissive hypothermia. Observation time was 3 hours. Endpoints were motor and somatosensory evoked potentials (motor evoked potentials and sensory evoked potentials), spinal cord perfusion pressure, cerebrospinal fluid pressure, regional spinal cord blood flow, and neurologic outcome. Animals with interrupted inflow into epidural arcades (Group Treatment "closed") had higher cerebrospinal fluid pressure levels (P < 0.05), were not able to maintain sufficient spinal cord perfusion pressure during Frozen Elephant Trunk procedure (P < 0.001) and did not generate reactive hyperemia as did group Treatment "open." spinal cord blood flow was strongly decreased in group Treatment "closed" (P < 0.001) at 0 hour, did not recover out to 3 hours of observation and 90% of the animals suffered flaccid paraplegia (P < 0.05). Immediate spinal cord backup blood flow is almost exclusively delivered using the system of epidural arcades in the immediate setting, serving as an immediate backup system. Intraspinal arcades are responsible for generating sufficient intraspinal perfusion pressures, reactive hyperemia, and spinal cord integrity. Paraspinal collaterals might need to undergo arteriogenesis, and thus serve as a long-term backup system.

Keywords: collateral blood flow; intraspinal arteries; spinal cord; thoracic aorta.