Cerebral Hemodynamic Changes Induced by Simulated Tracheal Intubation: A Possible Role in Perioperative Stroke?

Abstract

Background and Purpose —Perioperative stroke is a rare complication of generalized surgery (1% to 6%). Unexpected difficulties with tracheal intubation (TI), as well as the hyperextended position, may predispose a patient to or play a role in stroke. We sought to identify blood flow changes in carotid and vertebral arterial circulation during simulated TI and develop profile models for stroke risk before possible generalized surgery. Methods —One hundred sixty consecutive patients with suspected cerebral vascular disease or pending surgery underwent MR angiography with flow analysis. Simulated TI position was maintained for 3 to 4 minutes per acquisition. Results —The cohort consisted of 89 females (56%) and 71 males (44%) with a mean age of 66 years (range, 17 to 89 years). Hypoplastic vertebral arteries with flow less than 50 mL/s were present in 40 patients (25%). Profound alteration in basilar artery flow was noted in this group with increased frequency of microinfarctions on MRI (77% versus 38%). Unsuspected carotid occlusion (n=6) and vertebral artery occlusion (n=2) were associated with significant basilar artery flow changes. Flow reversal was present in five cases. Carotid arterial changes were not significant with simulated TI. No overt ischemic symptoms developed during these maneuvers. Conclusions —Simulated TI is safe yet induces distinct and potentially detrimental flow abnormalities. Individuals identified with the biological markers of hypoplasia, carotid and vertebral occlusion, severe stenosis, or prior ischemic vascular disease should receive special attention to neck position not only during surgery but also in the postoperative period. Sustained neck hyperextension greater than 12 minutes appears to be a neglected potential hemodynamic factor that may play a pivotal role in the pathogenesis of perioperative stroke.