The Use of Somatosensory Evoked Potentials to Determine the Relationship Between Intraoperative Arterial Blood Pressure and Intraoperative Upper Extremity Position-Related Neurapraxia in the Prone Surrender Position During Spine Surgery: A Retrospective Analysis.

BACKGROUND: Peripheral nerve injury is a significant perioperative problem. Intraoperative position-related neurapraxia may indicate impending peripheral nerve injury and can be detected by changes in somatosensory evoked potentials (SSEP). The purpose of this retrospective analysis of spine surgeries performed under general anesthesia with SSEP monitoring was to determine the relationship between intraoperative mean arterial blood pressure (MAP) and intraoperative upper extremity position-related neurapraxia in the prone surrender (superman) position. METHODS: We reviewed a computerized database of spine surgeries performed on adult patients in the prone surrender position. The authors reviewed intraoperative SSEP monitoring reports to identify the patients who developed intraoperative upper extremity position-related neurapraxia (case group) and patients who did not (control group). Propensity matching was performed to derive 2 demographically matched groups. Preoperative and intraoperative variables were included in the univariate Cox regression analysis of risk factors associated with neurapraxia. Multivariate Cox regression models were used to identify the independent risk factors. RESULTS: One hundred fifty-two patients were included in the analysis. The case group included 32 patients, whereas the control group included 120 matched patients. Intraoperative MAP <55 mm Hg for a total duration of ≥5 minutes was an independent risk factor associated with a greater incidence of upper extremity position-related neurapraxia compared with a duration of <5 minutes with MAP <55 mm Hg (hazard ratio, 3.43; confidence interval, 1.445-8.148; P = 0.0052). Intraoperative MAP >80 mm Hg for a total duration of >55 minutes was an independent predictor associated with a lower incidence of neurapraxia compared with a total duration ≤55 minutes (hazard ratio, 0.341; confidence interval, 0.163-0.717; P = 0.0045). CONCLUSIONS: In this study, we identified the changes in intraoperative MAP as independent predictors associated with upper extremity position-related neurapraxia in the prone surrender position under general anesthesia.