Changes in the bispectral index and cerebral oxygen saturation during neuroendovascular intervention under general anesthesia

Corresponding author: Kyung-Don Hahm, M.D., Ph.D., Department of Anesthesiology and Pain Medicine, Asan Medical Center, University of Ulsan College of Medicine, 388-1, Pungnap 2-dong, Songpa-gu, Seoul 138-736, Korea. Tel: 82-2-3010-5979, Fax: 82-2-3010-6790, E-mail: [email protected] This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http:// creativecommons.org/licenses/by-nc/3.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. CC Neuroendovascular interventions using coil embolization, stent insertion, or balloon-expander techniques are currently employed to treat intracranial aneurysms, arteriovenous malformations (AVMs), and cerebrovascular stenosis or occlusion. Several complications may occur during neurointervention, including rupture of vessels, vasospasm, thromboembolism, or catheter malposition. Techniques used to monitor complications associated with neurointervention include neurologic examination, electroencephalography (EEG), motorand somatosensory-evoked potentials, assessment of transjugular oxygen saturation, transcranial Doppler ultrasound monitoring, and measurement of cerebral oxygen saturation. Although the application and utility of near-infrared cerebral oxymetry during neuroendovascular intervention have been evaluated [1-3], statistical analysis was lacking and relatively small numbers of patients were studied. The bispectral index (BIS) is a complex parameter calculated from several EEG-derived sub-parameters, including the relative beta ratio, high-order bispectrum, and the burst suppression ratio. BIS has been widely used to evaluate sedative-hypnotic status during surgery under general anesthesia. However, to the best of our knowledge, no previous study has examined changes in BIS values during neurointerventions. Thus, the aim of the present study was to assess changes in BIS and regional cerebral oxygen saturation (rSO2) using near-infrared spectroscopy (NIRS) in anesthetized patients undergoing neuroendovascular interventions. This study was approved by our Institutional Review Board prior to study commencement. After written informed consent had been obtained from each patient or parents of adolescent patient, 28 patients (male 12, female 16), aged 14-81 years (mean 50.9 ± 14.3), undergoing elective neuroendovascular procedures conducted by neurointerventionists were enrolled in the study. Patients were diagnosed with cerebral aneurysms (n = 17), cerebral vascular stenosis (n = 2), AVMs (n = 8), or carotid tumor (n = 1). A BIS sensor and two cerebral oxymeter sensors were placed on the forehead of each patient to provide continuous and simultaneous monitoring of BIS and rSO2. General anesthesia was induced with target-controlled infusion (TCI) of propofol 3.0 μg/ml, remifentanil 5.0 ng/ml, and a bolus injection of 50 mg atracurium. Anesthesia was maintained with air (1.5 L/min) and oxygen (1 L/min), intermittent bolus injections of atracurium, and continuous infusion of propofol (2.0-3.0 μg/ml) and remifentanil (3.0-5.0 ng/ml). Hemodynamic, BIS, and rSO2 values were obtained immediately before and after, and 5 min after, neuroendovascular intervention (either embolization or stent insertion). The TCI rates of propofol and remifentanil did not change over this interval. All data are presented as means ± standard deviations. Statistical analysis was performed using SPSS version 12 (SPSS Inc., Chicago, IL, USA). All continuous parameters studied were evaluated using repeated measures analysis of variance. For all comparisons, a P value less than 0.05 was considered to be statistically significant.