Redox changes in cat brain cytochrome-c-oxidase after blood
-fluorocarbon exchange during transient and graded hypoxia.
Ferrari, M., M. A. Williams, D. A. Wilson, N. V. Thakor, R. J.
Traystman, and D. F. Hanley.
Departments of Anesthesiology/Critical Care Medicine, Neurology,
and Biomedical Engineering, The Johns Hopkins Medical Institutions,
Baltimore, MD 21287, Department of Biomedical Technology, University
of L'Aquila, 67100, L'Aquila, Italy
APStracts 2:0060H, 1995.
We used rapid scanning near infrared (NIR) spectroscopy (730-960 nm)
to study the effects of graded or acute hypoxia on cerebral
cytochrome-c-oxidase (cyt a,a3) redox state in blood-perfluorocarbon
exchanged cats with somatosensory evoked potential (SEP) monitoring.
In graded hypoxia (10-min each at FiO2 0.9, 0.8, 0.7, 0.6, 0.5), cyt
a,a3 reduction occurred at FiO2 0.6 when cerebral O2 delivery was
below 3.5 ml/100g/min. In acute hypoxia (FiO2 0.6 for 10 min),
significant cyt a,a3 reduction occurred from 5-10 min (cerebral O2
delivery 3.1 +/- 0.3 ml/100g/min) and recovered with re-oxygenation
(FiO2 1.0). Cyt a,a3 redox changes preceded or coincided with SEP
alterations in both hypoxia protocols. These results demonstrate that
cerebral cyt a,a3 reduction occurs with severe reduction of cerebral
O2 delivery, but no significant change in cerebral cyt a,a3 redox
state occurs with small reductions of cerebral O2 delivery. We
conclude that substantial changes in cerebral cyt a, a3 do not occur
at physiological levels of O2 delivery and that current NIR clinical
instruments would detect oxygen-dependent cerebral cyt a,a3 redox
changes only when O2 delivery is extremely compromised.
Received 14 March 1994; accepted in final form 22 February 1995.
APS Manuscript Number H241-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 10 March 1995.