Decision tree-based machine learning analysis of intraoperative vasopressor use to optimize neurological improvement in acute spinal cord injury.

OBJECTIVE: Previous work has shown that maintaining mean arterial pressures (MAPs) between 76 and 104 mm Hg intraoperatively is associated with improved neurological function at discharge in patients with acute spinal cord injury (SCI). However, whether temporary fluctuations in MAPs outside of this range can be tolerated without impairment of recovery is unknown. This retrospective study builds on previous work by implementing machine learning to derive clinically actionable thresholds for intraoperative MAP management guided by neurological outcomes. METHODS: Seventy-four surgically treated patients were retrospectively analyzed as part of a longitudinal study assessing outcomes following SCI. Each patient underwent intraoperative hemodynamic monitoring with recordings at 5-minute intervals for a cumulative 28,594 minutes, resulting in 5718 unique data points for each parameter. The type of vasopressor used, dose, drug-related complications, average intraoperative MAP, and time spent in an extreme MAP range (< 76 mm Hg or > 104 mm Hg) were collected. Outcomes were evaluated by measuring the change in American Spinal Injury Association Impairment Scale (AIS) grade over the course of acute hospitalization. Features most predictive of an improvement in AIS grade were determined statistically by generating random forests with 10,000 iterations. Recursive partitioning was used to establish clinically intuitive thresholds for the top features. RESULTS: At discharge, a significant improvement in AIS grade was noted by an average of 0.71 levels (p = 0.002). The hemodynamic parameters most important in predicting improvement were the amount of time intraoperative MAPs were in extreme ranges and the average intraoperative MAP. Patients with average intraoperative MAPs between 80 and 96 mm Hg throughout surgery had improved AIS grades at discharge. All patients with average intraoperative MAP > 96.3 mm Hg had no improvement. A threshold of 93 minutes spent in an extreme MAP range was identified after which the chance of neurological improvement significantly declined. Finally, the use of dopamine as compared to norepinephrine was associated with higher rates of significant cardiovascular complications (50% vs 25%, p < 0.001). CONCLUSIONS: An average intraoperative MAP value between 80 and 96 mm Hg was associated with improved outcome, corroborating previous results and supporting the clinical verifiability of the model. Additionally, an accumulated time of 93 minutes or longer outside of the MAP range of 76-104 mm Hg is associated with worse neurological function at discharge among patients undergoing emergency surgical intervention for acute SCI.

Quantitative assessment of locomotion and interlimb coordination in rats after different spinal cord injuries.

Animal models of spinal cord injury (SCI) are intended to mimic the main features of human spinal cord lesions, although sometimes it becomes a difficult task to find the right technique to discriminate the severity of the lesion as well as to assess different aspects of functional recovery. For this reason, we have used several functional methods to assess gross and fine locomotion deficits, as well as electrophysiological data to study the dysfunctions underlying the behavioral changes. Moreover, an extensive study based on the quantification of alternation and coordination parameters during gait has been done. Spinal cord injuries of varying severity (mild contusion, moderate contusion and hemisection) were performed at the thoracic level in adult rats that were followed-up for 6 weeks. Lesions resulting in similar scores in the open field test (i.e. mild contusion and hemisection) caused more marked differences in fine coordination when assessed by quantitative coordination analysis based on a digitized walking treadmill. In conclusion, gross and fine deficits can be detected using a battery of tests based on the performance of the animals during tasks of different difficulty. When used appropriately, they become useful tools to study functional recovery due to spontaneous plastic changes or to therapeutic interventions after SCI, as well as to test the effects of new therapies.