Cerebral vascular autoregulation is impaired following
resuscitation from
cardiac arrest (CA), and its quantification may allow assessing CA-induced
brain injury. However,
hyperemia occurring immediately post-
resuscitation limits the application of most metrics that quantify autoregulation. Therefore, to characterize autoregulation during this critical period, we developed three novel metrics based on how the cerebrovascular resistance (CVR) covaries with changes in cerebral perfusion pressure (
CPP): (i) θCVR, which quantifies the CVR vs
CPP gradient, (ii) a CVR-based transfer function analysis, and (iii) CVRx, the correlation coefficient between
CPP and CVR. We tested these metrics in a model of
asphyxia induced CA and
resuscitation using seven adult male Wistar rats. Mean arterial pressure (MAP) and cortical blood flow recorded for 30 min post-
resuscitation via arterial cannulation and
laser speckle contrast imaging, were used as surrogates of
CPP and cerebral blood flow (CBF), while CVR was computed as the
CPP/CBF ratio. Using our metrics, we found that the status of cerebral vascular autoregulation altered substantially during
hyperemia, with changes spread throughout the 0-0.05 Hz frequency band. Our metrics push the boundary of how soon autoregulation can be assessed, and if validated against outcome markers, may help develop a reliable metric of
brain injury post-
resuscitation.