Monitoring Flow in Extracranial-Intracranial Bypass Grafts Using Duplex Ultrasonography: A Single-Center Experience in 80 Grafts Over 8 Years

Abstract

Abstract BACKGROUND: High-flow extracranial-intracranial (EC-IC) bypass is performed by 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 to 2012 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: Eighty monitorable high-flow EC-IC bypasses were performed over the 8-year period. Sixty-five bypasses were performed by using RAGs and 15 were performed with SVGs. The average flow was 133 mL/min for RAGs and 160 mL/min for SVGs (P = .25). For both RAG and SVG groups, the donor and recipient vessel selected significantly impacted flow. For the RAG group only, preoperative graft diameter, postoperative hematocrit, and postoperative date significantly influenced flow. A 1-week average of >200 mL/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.