The influence of the duration of ischemia on the pattern of cerebral blood flow in recirculation was studied in anesthetised rats. Severe incomplete cerebral ischemia (mean ischemic flow = 5.8 +/- 0.4 ml/100 g/min) was produced by four-vessel occlusion and recirculation permitted after 15, 30 or 60 minutes ischemia. All three groups showed an immediate hyperemia followed by hypoperfusion. Hyperemia was maximal following 15 minutes ischemia and least pronounced following 60 minutes ischemia (p = 0.0249). Hypoperfusion started most quickly following 15 minutes ischemia and was delayed following 60 minutes ischemia (p less than 0.001). In established hypoperfusion there was no difference in flow between the three groups. The possible mechanisms of these changes in flow are discussed.

Animals↗

PubMedDate not supplied

Variations in mean cerebral blood flow under anesthesia at rest and during cortical activation.

More than one cerebral blood flow (CBF) measurement was performed on the same occasion in three groups of patients using the intracarotid 133Xenon technique. In the anesthetized group there was a highly significant reduction in CBF (mean = 24.3%) from the first to the second measurement. In those at rest under local anesthesia there was also a significant fall (mean 9.8%). The third group, who were stimulated during the second estimation, showed no change. A second CBF determination some time after beginning a study is recommended, especially in pharmacological studies, to provide a more reliable resting control, rather than the first value which represents flow in an "activated" brain which has not yet adapted fully to its new environment.

Adolescent↗

PubMedDate not supplied

Vaccination against dental caries.

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Dental Caries↗