[Reversibility of cerebral cortical function after recirculation in experimental cerebral ischemia]

Several kinds of monitoring systems to evaluate cerebral function have been introduced such as somatosensory evoked potential, visual evoked potential and auditory brain stem response. Although these monitoring systems are employed in practice in neurosurgical operations, the reversibility of these cerebral functions after ischemia insult is little known. In this study the reversibility of direct cortical response (DCR) as well as EEG from global ischemia was investigated using total 60 cats. Cortical cerebral blood flow was also measured continuously by the thermal diffusion flow probe with a peltier stack calibrated by hydrogen clearance. Global ischemia was made by the occlusion of innominate and left subclavian arteries. Although the EEG was abolished soon after occlusion of these arteries, DCR was preserved and it started to decay at the cortical CBF of about 21 ml/100 g/min. It had completely disappeared at the CBF of about 8 ml/100 g/min. Recovery of DCR was not correlated with the occlusion time, but it was well correlated with the interval of loss of DCR. When the DCR was not completely lost, DCR amplitude was completely recovered about 3 hours after ischemia insult with the CBF below 20 ml/100 g/min. Moreover, in all 8 cats which were recirculated within 5 minutes after loss of DCR, complete recovery of DCR amplitude was obtained. However, it was observed in 10 of 12 cats (83%) with 10 minutes loss of DCR, 5 of 12 cats (42%) with 15 minutes loss of DCR, 4 of 14 cats (29%) with 20 minutes loss of DCR, and only one of 11 cats (10%) with 30 minutes loss of DCR.(ABSTRACT TRUNCATED AT 250 WORDS)