F113. The methohexital challenge prior to intracranial endovascular embolization

Abstract

Introduction The risks associated with endovascular embolization procedures are both mitigated and predicted with the use of pharmacologic provocative testing (PT) and intraoperative neurophysiologic monitoring (IONM). The utility of pharmacologic provocative testing has been reviewed in the literature, mostly in patients undergoing awake procedures with the use of neurologic examination and electroencephalogram. Here, we review our experience in patients undergoing intracranial endovascular embolization procedures with the use of IONM. Methods We reviewed our database to identify all patients undergoing endovascular procedures between January 1, 2014 and January 1, 2016. We included only patients who underwent cerebral endovascular embolization procedures with the use of methohexital PT. A retrospective chart review was performed to identify patients’ demographic factors, intraoperative findings, and postoperative examination details. We also reviewed perioperative notes to identify any adverse reactions to methohexital as well as other complications unrelated to the use of methohexital. Awake patients were tested with SSEP, EEG and real time neurologic examination while TcMEPs were performed in all anesthetized patients. BAEPs were performed in anesthetized patients if indicated. Methohexital was administered as an injection at a dose of 5 mg or 10 mg and repeat testing was performed if needed. Results A total of 64 endovascular procedures were performed in 31 patients with utilization of pharmacologic PT and were included in this review. PT was performed under general anesthesia in 54 procedures (84%) and awake testing was performed in 10 procedures (16%). PT was negative in 62 procedures and embolizations were performed in these patients. PT was positive in two procedures and the procedure was terminated without embolization in one patient. The other patient underwent embolization after repositioning the catheter at an alternative embolization site but repeat testing was not performed. There were no new postoperative neurologic deficits after any of these procedures. We calculated the specificity of pharmacologic PT as 100% as none of the patients with a negative provocative test developed a new postoperative neurologic deficit after embolization. Conclusion To the best of our knowledge, this is the first review on pharmacologic PT with methohexital and with the use of IONM under general anesthesia. Our results also indicate that IONM under general anesthesia can allow pharmacologic PT at a specificity comparable to awake testing. We also postulate that the absence of false negatives provides strong evidence that IONM accurately monitors the functional state of the brain during PT. If this were not the case, then new neurologic deficits should be seen in some of the cases with negative tests.