Background: High-flow extracranial-to-intracranial (EC-IC) bypass is performed using radial artery graphs (RAGs) or saphenous vein grafts (SVGs) for various pathologies such as aneurysms, ischemia, and skull-base tumors. Quantifying the acceptable amount of blood flow to maintain proper cerebral perfusion has not been well established, nor have the variables that influence flow been determined.
Objective: To identify the normative range of blood flow through extracranial-intracranial RAGs and SVGs as measured by duplex ultrasonography. Multiple variables were evaluated to better understand their influence of graft flow.
Methods: All EC-IC grafts performed at Harborview Medical Center from 2005-20012 were retrospectively reviewed for this cohort study. Daily extracranial graft duplex ultrasonography with flow volumes and transcranial graft Doppler were examined, as were short- and long-term outcomes. Both ischemic and hyperemic events were evaluated in further detail.
Results: 80 monitorable high-flow EC-IC bypasses were performed over the 8-year period. Sixty-five bypasses were performed using RAGs and 15 with SVGs. The average flow was 133 ml/min for RAGs and 160ml/min for SVGs (p=0.25). For both RAG and SVG groups, the donor and recipient vessel selected significantly impacted flow. For the RAG group only, pre-operative graft diameter, post-operative hematocrit, and post-operative date significantly influenced flow. A 1-week average of >200ml/min was 100% sensitive to cerebral hyperemia syndrome.
Conclusion: This study establishes the normative range of duplex ultrasonographic flow after high-flow EC-IC bypass as well the usefulness and practicality of such monitoring as a surrogate to flow in the postoperative period.
From: Monitoring Flow in EC-IC Bypass Grafts Using Duplex Ultrasonography: A Single Center Experience in 80 Grafts Over 8 Years by Sekhar et al.