Predictive Factors for Hypotension Associated With Supine-to-Prone Positional Change in Patients Undergoing Spine Surgery

Abstract

Positional change during general anesthesia can cause hypotension. The objective of this retrospective study was to determine predictive factors for hypotension associated with supine-to-prone positional change in spinal surgery patients. Data on demographics, current medications, comorbidity, intraoperative mean arterial pressure (MAP), heart rate, pulse pressure variation, tidal volume, peak inspiratory pressure, and propofol and remifentanil effect-site concentrations were collected from 179 patients undergoing elective spine surgery. Hypotension associated with supine-to-prone positional change was defined as >20% reduction in MAP during positional change. Hypotension associated with supine-to-prone positional change was observed in 16 (8.9%) patients. The median (interquartile range) effect-site concentration of remifentanil (5.3 [4.0 to 8.5] vs. 4.0 [3.1 to 4.0] ng/mL, P<0.001), MAP (95.0 [86.0 to 103.5] vs. 80.0 [70.0 to 94.0] mm Hg, P=0.014), peak inspiratory pressure (16.5 [15.0 to 18.5] vs. 15.0 [14.0 to 17.0] hPa, P=0.040) in the supine position, and pulse pressure variation in the prone position (12.0 [9.0 to 16.4] vs. 9.0 [7.0 to 12.0]%, P=0.019) were significantly higher in the hypotension group. In multivariate logistic regression analysis, the effect-site concentration of remifentanil (odd ratio [95% confidence interval], 2.12 [1.51-2.96], P<0.001), preoperative use of beta-blocker (7.64 [1.21-48.36], P=0.031), and MAP in the supine position (1.04 [1.00-1.07], P=0.033) were independent predictive factors for hypotension associated with supine-to-prone positional change. Increased effect-site concentration of remifentanil, preoperative use of beta-blocker, and high MAP in the supine position were predictive factors for hypotension associated with supine-to-prone positional change in spinal surgery patients.