Effect of Preischemia Cyclooxygenase Inhibition by Zomepirac Sodium on Reflow,Cerebral Autoregulation,and EEG Recovery in the Cat after Global Ischemia

Zomepirac sodium (ZS) (5 mg/kg i.v.) was used to evaluate the effects of preischemia cyclooxygenase inhibition on CBF (as assessed by ¹³³Xe clearance), CBF–P_aCO₂ responsiveness, and electrophysiologic (EEG) parameters before and after a 15-min period of complete global ischemia produced by four-vessel occlusion and mild hypotension. During the 15-min period of ischemia, CBF was essentially zero. Following reflow all groups displayed an initial hyperemia as compared with control (92 ± 11 vs. 141–146 ml/100 g/min). Saline-treated animals during reflow displayed a delayed hypoperfusion (26 ± 3 ml/100 g/min), which showed no improvement during the 2-h reflow period prior to death. In contrast, ZS-treated animals during reflow displayed significantly higher flows during the hypoperfusion phase (72 ± 9 ml/100 g/min). The CBF–P_aCO₂ response displayed an approximately sevenfold reduction in slope at 2 h after reflow in saline-treated animals. This decrease in P_aCO₂ reactivity was not observed in the ZS-pretreated animals. With regard to EEG, all animals showed a total flattening during the 15 min of ischemia. In saline-treated animals only one of seven showed any sign of even marginal recovery. In ZS-treated animals EEG activity showed prominent recovery in seven of seven. Brainstem auditory evoked potentials were monitored and showed prominent recovery of amplitude and latency in ZS but not saline-treated animals during reflow.