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FAILURE OF THE NITROUS OXIDE TISSUE EQUILIBRATION METHOD FOR THE DETERMINATION OF BRAIN AND MYOCARDIAL BLOOD FLOW UNDER CONTROLLED CONDITIONS
Author(s) -
Reid Michael A.,
Runciman William B.,
McLean Colin F.,
Mather Laurence E.
Publication year - 1992
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1992.tb00443.x
Subject(s) - nitrous oxide , coronary sinus , blood flow , chemistry , arterial blood , saturation (graph theory) , anesthesia , cardiology , chromatography , medicine , mathematics , combinatorics
SUMMARY 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 (N 2 O) for 60 min. Serial measurements of brain and myocardial blood flow were made using the N 2 O tissue equilibration method of Kety and Schmidt. 3. N 2 O 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.