Exploration of surgical blood pressure management and expected motor recovery in individuals with traumatic spinal cord injury

Abstract

Study design: Retrospective analysis.

Objective: To assess the impact of mean arterial blood pressure (MAP) during surgical intervention for spinal cord injury (SCI) on motor recovery.

Setting: Level-one Trauma Hospital and Acute Rehabilitation Hospital in San Jose, CA, USA.

Methods: Twenty-five individuals with traumatic SCI who received surgical and acute rehabilitation care at a level-one trauma center were included in this study. The Surgical Information System captured intraoperative MAPs on a minute-by-minute basis and exposure was quantified at sequential thresholds from 50 to 104 mmHg. Change in International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) motor score was calculated based on physiatry evaluations at the earliest postoperative time and at discharge from acute rehabilitation. Linear regression models were used to estimate the rate of recovery across the entire MAP range.

Results: An exploratory analysis revealed that increased time within an intraoperative MAP range (70-94 mmHg) was associated with ISNCSCI motor score improvement. A significant regression equation was found for the MAP range 70-94 mmHg (F[1, 23] = 5.07, r² = 0.181, p = 0.034). ISNCSCI motor scores increased 0.039 for each minute of exposure to the MAP range 70-94 mmHg during the operative procedure; this represents a significant correlation between intraoperative time with MAP 70-94 and subsequent motor recovery. Blood pressure exposures above or below this range did not display a positive association with motor recovery.

Conclusions: Hypertension as well as hypotension during surgery may impact the trajectory of recovery in individuals with SCI, and there may be a direct relationship between intraoperative MAP and motor recovery.

Fig. 1

Serial regression analysis between MAP exposure and ISNCSCI motor score changes. Representative figures (a–d) illustrate individual regressions between 5-unit MAP bins and changes in ISNCSCI motor scores. A trend line, confidence intervals, and trend line equation are included in the representative figures. Each point in the representative figures corresponds to an individual. Linear regressions with positive slope (green) signify greater improvement in motor score based on increased exposure within a defined MAP range. Negative slopes (red) signify greater improvement in motor score based on decreased exposure within a defined MAP range. A negative slope does not represent deterioration of individual motor scores. e summarizes the 11 individual 5-unit MAP bin regressions. The x axis represents the MAP bins and the y axis represents the slopes (betas) for the individual regressions. Each point includes its corresponding 95% confidence interval, illustrated as an error bar. The gray region represents the optimal MAP range identified in this analysis

Fig. 2

Change of ISNCSCI motor score vs. minutes within each MAP range during surgery. a–c Linear regression of ISNCSCI motor scores change (discharge—post-surgery) vs. minutes within each MAP range during surgery; each point represents an individual. Positive slopes (green) signify greater improvement in motor score based on increased exposure within a defined MAP range. Negative slopes (red) signify greater improvement in motor score based on decreased exposure within a defined MAP range. A negative slope does not represent deterioration of individual motor scores. d Graph of slopes for each linear regression analysis; each point represents the slope of regression line. Colored points correspond to slopes of (a−c) and error bars correspond to the 95% confidence interval of the slope (beta)

Fig. 3

Surgical time outside 70–94 MAP range and 85–90 MAP range for individuals with no improvement versus individuals with improvement. Each figure represents the distribution of time (minutes) spent outside the optimal (70–94 mmHg) and CNS/AANS (85–90 mmHg) recommended MAP ranges for the improvement and no improvement groups. The figure on the left represents the optimal range identified in the regression analysis, while the figure on the right represents the CNS/AANS-recommended range. Each point represents an individual and the lines represent the median exposure time for the group