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Type: Journal article
Title: Cerebrovascular carbon dioxide reactivity in sheep: Effect of propofol or isoflurane anaesthesia
Author: Myburgh, J.
Upton, R.
Ludbrook, G.
Martinez, A.
Grant, C.
Citation: Anaesthesia and Intensive Care, 2002; 30(4):413-421
Publisher: Australian Soc Anaesthetists
Issue Date: 2002
ISSN: 0310-057X
Statement of
J. A. Myburgh, R. N. Upton, G. L. Ludbrook, A. Martinez, C. Grant
Abstract: Propofol and isoflurane are commonly used in neuroanaesthesia. Some published data suggest that the use of these agents is associated with impaired cerebral blood flow/carbon dioxide (CO₂) reactivity. Cerebrovascular CO₂ reactivity was therefore measured in three cohorts of adult merino sheep: awake (n=6), anaesthetized with steady-state propofol (15 mg/min; n=6) and anaesthetized with 2% isoflurane (n=6). Changes in cerebral blood flow were measured continuously from changes in velocities of blood in the sagittal sinus via a Doppler probe. Alterations in the partial pressure of carbon dioxide in arterial blood (PaCO₂) over the range 18-63 mmHg were achieved by altering either the inspired CO₂ concentration or the rate of mechanical ventilation. Cerebral blood flow/CO₂ relationships were determined by linear regression analysis, with changes in cerebral blood flow expressed as a percentage of the value for a PaCO₂ of 35 mmHg. Propofol decreased cerebral blood flow by 55% relative to pre-anaesthesia values (P=0.0001), while isoflurane did not significantly alter cerebral blood flow (88.45% of baseline, P=0.39). Significant linear relationships between cerebral blood flow and CO₂ tension were determined in all individual studies (r2 ranged from 0.72 to 0.99). The slopes of the lines were highly variable between individuals for the awake cohort (mean 4.73, 1.42-7.12, 95% CI). The slopes for the propofol (mean 2.67, 2.06-3.28, 95% CI) and isoflurane (mean 2.82, 2.19-3.45, 95% CI) cohorts were more predictable. However, there was no significant difference between these anaesthetic agents with respect to the CO₂ reactivity of cerebral blood flow.
Keywords: Animals; Sheep; Carbon Dioxide; Isoflurane; Propofol; Anesthetics, Inhalation; Anesthetics, Intravenous; Ultrasonography, Doppler; Blood Flow Velocity; Linear Models; Blood Pressure; Cerebrovascular Circulation; Intracranial Pressure; Hydrogen-Ion Concentration; Female
Description: Publisher's copy made available with the permission of the publisher © Australian Society of Anaesthetists
RMID: 0020020158
DOI: 10.1177/0310057X0203000402
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Appears in Collections:Anaesthesia and Intensive Care publications

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