A series of cats were subjected to MCAO. During the ischemia, the regional cerebral blood flow (rCBF) generally fell to less than about 12 ml/100g/min. The CEI rose rapidly within 3-4 minutes and reached 150% or more within 10 minutes. Following the rapid rise phase, a second phase of increase in impedance occurred but at a much slower rate. Upon release of the occlusion, the impedance began to fall within less than a minute. This drop was precipitous at first, but more gradual with time. If the duration of ischemia was short (less than 1 hr) the CEI recovered to the base control value. In longer duration occlusions (1 hr or more) the CEI appeared to not recover completely and often trended up. This secondary rise was considered to be related to brain compression produced by brain edema.
