140. Rapid reversal of surgical steps minimizes spinal cord injury in a porcine model

Abstract

BACKGROUND CONTEXT Spinal cord injuries (SCI) are one of the most devastating in spine surgery. Intraop neuromonitoring changes can occur as a secondary characteristic of spinal cord compression and decrease in spinal cord blood flow (SCBF). Laser Doppler flowmetry has been well validated for measuring SCBF. PURPOSE To determine if critical, measurable changes occur before spinal cord injury occurs. STUDY DESIGN/SETTING Porcine model. PATIENT SAMPLE Seventeen pigs. OUTCOME MEASURES Spinal cord blood flow, MEP, MAP, neurological injury, spinal canal volume. METHODS After prone positioning and induction, multilevel laminectomies are performed in the midthoracic region. LDF electrodes were placed on the exposed dura in multiple areas to measure real-time SCBF. Spinal cord injury was induced by incremental balloon inflation in the epidural space. After MEP loss (SCI), interventions were carried out: raising the systolic BP, expanding the intravascular volume with colloids, and IV lidocaine. After interventions, wake up test is performed and CT scan was done to measure the thoracic spinal canal volume. Two groups based on intervention timing. Group A: medical interventions before balloon deflation; Group B: balloon deflated first. RESULTS Seventeenpigs were studied, 14 of which survived and completed the experiment. Recordable SCBF changes from baseline were seen 3–32 minutes before MEP loss. For this reason, we considered three minutes to be the critical time before SCI. However, the 20% threshold interval was often reached before the 3-minute mark. Three minutes before MEP loss, change in SCBF was −24.9% and balloon pressure was 9 psi. Balloon volume was 0.63 cc. The spinal canal compromise 3 minutes before MEP signals loss was 69.3%, while SCBF three minutes before MEP loss was 71. This was a 24.85% change from baseline SCBF. In Group A, no pigs moved. In Group B, 9/10 were found to be moving their hind legs. CONCLUSIONS Compression SCI is the end of a cascade involving increasing pressure, decreasing volume and hypoperfusion. Rapid relief of compression leads to MEP return and function. SCBF monitoring can detect ischemia preinjury, giving surgeons an opportunity for early intervention. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.