Author response: Spinal cord perfusion pressure predicts neurologic recovery in acute spinal cord injury

We thank Dr. Satyarthee for the comments about our article.¹ It is correct that we did not correlate the spinal cord perfusion pressure (SCPP) with mean arterial pressure (MAP); however, because SCPP is mathematically calculated from MAP, there is a relationship between the two by default. The important finding is that they are not equivalent with regards to predicting subsequent neurologic recovery. We recognize that SCPP is dynamic and that the optimal SCPP remains unknown (and probably differs from patient to patient). By statistically iterating through all possible cutoffs, we identified 50 mm Hg of SCPP as the point below which an increased risk for poor neurologic improvement starts to appear (figure 2).¹ This 50 mm Hg threshold was not chosen arbitrarily, as Dr. Satyarthee suggests. As for the small sample size, we accept this limitation; the MAP goal of 85–90 mm Hg recommended in the 2013 guidelines that Dr. Satyarthee cites is largely based upon 2 studies with cohorts considerably smaller than ours.^2,3 Nonetheless, we concur that further work is needed to define the role of SCPP monitoring in acute spinal cord injury.