The Art and the Logic of Flow-Guided Bypass for Aneurysms

The flow-guided approach to cerebrovascular surgery represents an important paradigm shift in bypass for aneurysms. The critically important conceptual starting point is that a bypass for an aneurysm is a “flow replacement bypass.” Bypass in complex cerebral aneurysm surgery becomes necessary when blood flow must be replaced during clip ligation or reconstruction, such that a new conduit must be established to revascularize the efferent vessels of the aneurysm. Classical teaching considered the terms “high flow” or “low flow” in reference to the donor vessel size, attempting to approximate the flow available and ranging from saphenous veins to radial artery to in situ pedicles. However, a supply-demand conceptual framework developed over the past two decades that highlighted the importance of direct intraoperative flow measurement to guide decision-making. Ultimately, the best revascularization approach matches donor supply to recipient demand, and that assessment must be performed at an individual case level. Therefore, using real-time direct flow measurements intraoperatively during bypass surgery for cerebral aneurysms provides critical information for donor selection and about bypass patency. This chapter will review the preoperative assessment, surgical technique, and postoperative management in the flow-guided bypass for aneurysms.