Abstract
The purpose of this study is to clarify significance of both induced mild hypercapnia and mild hypertension as preoperative tests predicting postoperative result of STA-MCA bypass on functional recovery of ischemic brain.
Cerebral ischemia was produced by occlusion of canine middle cerebral artery and changes of somatosensory evoked potentials (SEP, V1) and regional cerebral blood flow (rCBF) were monitored for three hours following production of ischemia, under CO2 inhalation or with a controlled intravenous infusion of Angiotensin II
From this study we obtained next results.:
1) In mild ischemia whose rCBF was decreased by 20 to 40% compared to control, rCBF and SEP (V1) significantly recovered during artificially induced mild hypercapnia (PaCO2 43 to 55 mmHg). However, mild hypertension caused no or minimal changes on rCBF and SEP (V1) in the ischemia of this degree.
2) In moderate ischemia, rCBF of which reduced by 40 to 60% compared to control. rCBF and SEP (V1) were significantly restored by artificially induced mild hypertension. Conclusion:
Induced mild hypercapnia and mild hypertension methods are hopeful as preoperative tests predicting postoperative result of bypass surgery. However, care is needed on assessing the results of these tests, since response of cerebral arteries by two activation methods depends on degree of ischemia.
