Failure of the nitrous oxide tissue equilibration method for the determination of brain and myocardial blood flow under controlled conditions.
1. Two adult merino ewes were prepared with intravascular cannule for sampling aortic root blood, sagittal sinus blood and coronary sinus blood. 2. One week after preparation the animals were anaesthetized then ventilated with a gas mixture containing 10% nitrous oxide (N2O) for 60 min. Serial measurements of brain and myocardial blood flow were made using the N2O tissue equilibration method of Kety and Schmidt. 3. N2O failed to achieve matching arteriovenous blood concentration equality and saturation of the relevant tissues. Valid use of the Kety-Schmidt method, therefore, could not be confirmed. 4. Because of the failure of the arteriovenous equilibration, serially determined brain and myocardial blood flows were found to decrease with time. 5. The use of this method in circumstances where tissue saturation with the indicator gas cannot be ascertained is arbitrary.
Reid
M A
MA
Department of Anaesthesia and Intensive Care, Flinders Medical Centre, Flinders University of South Australia, Adelaide, South Australia.
Runciman
W B
WB
McLean
C F
CF
Mather
L E
LE
D000818:Animals; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003326:Coronary Circulation / Q000502:physiology*; D005260:Female; D009609:Nitrous Oxide / Q000032:analysis / Q000493:pharmacokinetics; D012756:Sheep
D009609:Nitrous Oxide