Intra-operative transit time flowmetry reduces the risk of ischemic neurological deficits in neurosurgery

Intra-operative transit time flowmetry (ITTF) can be used to quantify blood flow in local at risk vessels before and after surgical intervention. As inadvertent vessel compromise represents a major cause of neurological deficit following neurovascular surgery, the purpose of this study was to assess this technology in terms of its indications, ease of implementation and interpretation, safety and reliability. Patients were prospectively invited to participate. ITTF was recorded from at-risk vessels before and after surgical intervention, along with blood pressure and PaCO2. Any episodes of flow compromise or change in surgical procedure were noted and correlated with post-operative neurological deficits and imaging. Twenty-eight patients undergoing 30 craniotomies were enrolled. Operations included n = 21 aneurysm clipping or exploration, 2 AVM excision, 2 dural AV fistula disconnections, 2 EC-IC bypass and 3 tumor resections. ITTF led to an alteration in surgery in 8 of the 30 cases (27%). In patients undergoing aneurysmal surgery, inadvertent vessel occlusion was identified in 3 cases, which led to immediate repositioning of the aneurysm clips. In 2 AV fistulae and 2 AVM surgeries, markedly reduced draining vein flow rates were confirmed quantitatively immediately before final surgical disconnection was carried out. In 1 EC-IC bypass patient, the measurement suggested graft vasospasm then treated with papaverine. One aneurysm person awoke with a stroke presumably from an embolic event undetected by ultrasonography. ITTF provides immediate feedback regarding vessel patency. Clip-related arterial compromise and local vasospasm are detected by this technology, but an embolic event may escape detection. This technology was found to have a broad utility in intra-cranial surgery, and was safe, rapidly performed, easy to interpret and generally reliable.