1266 Dynamic Effects of Different Vasopressors on Spinal Cord Blood Flow Through the Sulcal Arteries

INTRODUCTION: Following spinal cord injury (SCI), treatment includes vasopressors to elevate mean arterial pressure (MAP) to preserve blood flow at the injury. However, this is based on limited understanding of how vasopressors interact with spinal vasculature. Specifically, α- and β-adrenergic receptors have been implicated in vasoconstriction and vasodilation, respectively, in the central nervous system. Depending on the affinity of pressors to each receptor, differential effects on blood flow may occur. METHODS: A T4-T6 laminectomy was performed on five 30 kg Yorkshire pigs. An ultrasound probe was secured over the cord to measure sulcal artery flow using spectral Doppler. MAP was elevated using phenylephrine (α), epinephrine (α+β), and dobutamine (β) and measured via femoral arterial catheter. Each pig underwent multiple MAP challenges with 10-minute washouts. The spectral Doppler signal was analyzed to obtain flow velocity and power Doppler, an estimate of volumetric flow. RESULTS: For each pressor, increased MAP resulted in similar changes to sulcal artery velocity (middle panels). However, the vasopressors showed differences in power Doppler, with flow after phenylephrine and epinephrine returning to baseline rapidly but remaining elevated after dobutamine (bottom right). All pressors resulted in statistically significant increases in flow velocity, but only dobutamine resulted in an increase in power (p=0.01). CONCLUSIONS: Although increases in MAP corresponded to increases in flow velocity with all three drugs, only dobutamine resulted in an increase in power Doppler. Since power Doppler is a surrogate for volumetric flow, this implies that there are different effects on perfusion depending on the degree of α- or β -agonism. With additional studies, dobutamine may emerge as the preferred MAP augmentation agent following SCI.