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A comparison of regional cerebral blood flow measurements made with beta- and gamma-emitting isotopes revealed good correspondence in areas of normal perfusion and reactive hyperemia but poor correspondence in areas of focal ischemia. After middle cerebral artery occlusion at normocapnia, there was a 65% reduction in regional cerebral blood flow from 1.40 plus or minus 0.27 ml/g min--1 to 0.49 plus or minus 0.10 ml/g min--1 in monkeys studied with 85Kr but only a 27% reduction in regional cerebral blood flow from 0.84 plus or minus 0.09 ml/g min--1 to 0.61 plus or minus 0.08 ml/g min--1 in monkeys studied with 133Xe. The lack of correlation within areas of focal, incomplete ischemia was attributed to an impairment of isotope delivery to the area of ischemia coupled with the inherent lack of spatial resolution of determinations made with 133Xe. This finding may partly explain the numerous discrepancies in experimental and clinical studies of the effects of alterations in the arterial partial pressure of CO2 on regional cerebral blood flow in areas of ischemia; it may also explain the failure of such studies to reflect the true severity of focal ischemia.

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Established respiratory infections with mucoid Pseudomonas aeruginosa in patients suffering from cystic fibrosis were treated with conventional as well as larger doses of tobramycin. The infection was eradicated in four of the 17 patients treated, but the duration of follow-up study of one patient was short. It appeared that treatment was most successful in those patients in whom the highest peak concentrations of tobramycin in sputum were obtained. No side effects were noted, even when tobramycin was given in large doses for two weeks.

Abstract:Influence of Cerebral Vasoconslricting and Vasodilating Agents on Blood Flow in Regions of Focal Ischemia• Regional cerebral blood flow (rCBF) measurements with krypton-85 (100 separate determinations) were compared in squirrel monkeys anesthetized with sodium pentobarbital (a cerebral vasoconstrictor) and halothane (a cerebral vasodilator) before, during, and after middle cerebral artery (MCA) occlusion. Prior to MCA occlusion, a normal physiological response to alterations in arterial carbon dioxide tensions (Paco,) was demonstrated in both groups of monkeys; the cerebral vascular resistance was significantly lower in those anesthetized with halothane. During ischemia, there was loss of autoregulation and a failure to respond to alterations in Paco, in both groups. Flow in the ischemic region remained uniform in the barbiturate group but decreased progressively in the halothane group, suggesting a "paradoxical response" to the dilating agent. Reactive hyperemia (luxury perfusion) was demonstrated in both groups after restoration of flow. The use of a beta-emitting isotope ensured that measurements in regions of ischemia accurately reflected rCBF and were free of the artifacts ("look through" and Compton scatter) related to use of a gamma-emitting indicator.