The effect of Sedation Depth Regulation Monitored by Bispectral Index (BIS) during General Anesthesia on the Outcomes of Patients with ChronicConsciousness Disorders Undergoing Spinal Cord Stimulation Implantation: A real-world retrospective study
Authors: Chen Xuanling , Qin Xuewei , Zhuang Yutong , Li Zhengqian , Liang Zhenhu , Zhang Hua , Yao Lan , Li Xiaoli , He Jianghong , Guo Xiangyang 
Published: October 2023

Abstract
Objective: The objective of this study was to observe the effect of Bispectral Index (BIS)-monitored depth regulation of general anesthesia on the prognosis of patients with chronic disorders of consciousness (DOC) undergoing Spinal Cord Stimulation (SCS) implantation.
Methods: A total of 92 DOC patients who underwent SCS implantation under general anesthesia were followed up for 3 months after surgery. Among them, 83 patients met the inclusion criteria and were divided into the BIS group (n=67) and non-BIS group (n=16). Patient characteristics, such as gender, age, height, etiology, medical history, anesthetic drugs used, BIS utilization, blood gas parameters, cortisol levels, and output, were recorded. Coma Recovery Scale-Revised (CRS-R) scores and outcomes were assessed before surgery, 3 days post-surgery, and 3 months post-surgery.
Results: A total of 83 patients were included, with 67 patients in the BIS monitoring group and 16 patients in the non-BIS monitoring group. The causes of DOC included traumatic brain injury (TBI) in 33 cases, cerebrovascular disease (CVD) in 45 cases, and ischemia and anoxia (IAA) in 5 cases. There was no statistical difference in CRS-R3d scores and CRS-R preoperative score between the BIS monitoring group and the non-BIS monitoring group before surgery (P > 0.05). However, the CRS-R3m scores at 3 months post-surgery were significantly higher than the CRS-R preoperative score in both the BIS group and the non-BIS group (P < 0.05). There was no significant difference in the diagnoses between preoperative and 3 months post-surgery assessments in both groups (P > 0.05). In DOC patients with thalamic injury, BIS monitoring was correlated with the extent of thalamic injury (AUC=0.823, P=0.002). Similarly, in DOC patients with brain stem injury, BIS monitoring was correlated with the extent of brain stem injury (AUC=0.691, P=0.048). Blood gas analysis revealed that glucose levels were higher in the BIS group compared to the non-BIS group, and this difference was statistically significant (P < 0.05). In the BIS group, postoperative glucose levels were higher than preoperative levels (t=2.361, P =0.021). The use of dexmedetomidine as part of general anesthesia was found to be a risk factor associated with no improvement in CRS-R3d scores (r=1.409, P=0.033). A positive correlation was observed between BISawake and CRS-Rpreoperative scores, with a correlation coefficient of 0.47 (P =0.00). In the BIS group, 47.77% of patients showed improved consciousness, 50% remained unchanged, and 2.98% experienced decreased consciousness. In the non-BIS monitoring group, 31.11% showed improved consciousness, 44.35% remained unchanged while 69% experienced decreased consciousness.
Conclusion: In patients with chronic disorders of consciousness (DOC) undergoing Spinal Cord Stimulation (SCS) implantation under general anesthesia, the utilization of Bispectral Index (BIS) monitoring to regulate the depth of sedation has been shown to improve postoperative outcomes. This approach is also correlated with the preoperative Coma Recovery Scale-Revised (CRS-R) score. To ensure the accuracy of the CRS-R assessment, it is recommended to use propofol, sevoflurane, and remifentanil for anesthesia maintenance, thereby avoiding the potential effect of dexmedetomidine on postoperative CRS-R3d scores.