Predictive factors of unacceptable movement and motor-evoked potentials during intraoperative neurophysiological monitoring in adult patients undergoing brain surgery: A retrospective study

Motor-evoked potential (MEP) monitoring is an essential monitoring for clinicians to improve outcomes. Although unacceptable movement during MEP is a rare complication but it can lead to terrible results. The aim of this study was to evaluate the risk factors associated with unacceptable movements in patients undergoing brain surgery with MEP monitoring. We performed a retrospective observational study of patients who underwent brain surgery with MEP monitoring under general anesthesia while using a partial neuromuscular blocker in a tertiary care hospital from January 2014 to August 2017. Unacceptable movement was defined as a condition in which MEP stimulation induced vigorous movement of patient hindered the smooth progress of the operation. We compared the baseline patient characteristics and laboratory results according to unacceptable movements during surgery to identify factors associated with unacceptable movement during MEP monitoring. 768 patients were included in this analysis, and unacceptable movements were observed in 278 patients (36.2%). A multivariate logistic regression analysis revealed that an increase in ionized calcium was associated with the most strongly unpredictable movement during surgery [odds ratio (OR): 1.79, 95% confidence interval (CI): 1.37–2.36, P < .001]. In addition, age (OR, 0.98; 95% CI, 0.96–0.99; P = .001), male sex (OR, 1.59; 95% CI, 1.09-2.33; P = .017), and body mass index (OR, 0.90; 95% CI, 0.86-0.95; P <0.0010) were also associated with unacceptable movement. Serum ionized calcium concentration was the best predictor associated with unacceptable movement with MEP monitoring under general anesthesia. Serum ionized calcium concentration was the best predictor associated with unacceptable movement with MEP monitoring under general anesthesia.