Measurement of cerebral blood flow and volume with positron emission tomography during isoflurane administration in the hypocapnic baboon

Abstract

Using positron emission tomography, cerebral blood flow (CBF) and cerebral blood volume (CBV) were measured after the addition of isoflurane (1.3 vols %, end-tidal concentration) to neuroleptanesthesia (fentanyl/droperidol) in hypocapnic baboons. The study was designed to determine whether isoflurane, when administered during hypocapnia, acted as a cerebral vasodilator to increase either CBF or CBV. Mean arterial pressure was maintained within 10% of preisoflurane levels within an angiotensin infusion. In the first protocol (A), CBF and CBV were measured as close together in time as possible in order to detect divergent effects of isoflurane on these variables. When Pa(CO2) was reduced from 40 mmHg to 25 mmHg, CBF decreased from 44 ± 4 to 31 ± 4 ml·100 g-1·min-1 (P < 0.05) and CBV decreased from 3.1 ± 0.3 to 2.6 ± 0.3 ml/100 g (P < .05) and addition of isoflurane did not change CBV. From these results the authors conclude that in the normal hypocapnic baboon the addition of 1.3% isoflurane does not significantly change cerebral blood flow or volume.