AJP - Heart and Circulatory Physiology, Vol 244, Issue 3 320-H327, Copyright © 1983 by American Physiological Society
Hemodynamic responses to acute carboxyhemoglobinemia in the rat
W. E. Kanten, D. G. Penney, K. Francisco and J. E. Thill
The effects of carbon monoxide on the hemodynamics of the adult rat were
investigated. A number of parameters were measured using an open-chest,
chloralose-urethan anesthetized preparation. Our experiments showed this
anesthetic agent to have several advantages over pentobarbital sodium. One
group inhaled 150 ppm CO for 0.5-2 h, carboxyhemoglobin (HbCO) reaching
16%. Heart rate, cardiac output, cardiac index, dF/dtmax (aortic), and
stroke volume rose significantly; mean arterial pressure, total peripheral
resistance, and left ventricular systolic pressure fell, whereas stroke
work, left ventricular dP/dtmax, and stroke power changed little. These
effects were evident at a HbCO saturation as low as 7.5% (0.5 h). A second
group inhaled 500 ppm CO for 5-48 h, HbCO reaching 35-38%. The same
parameters changed in the same direction as in the first group, with mean
arterial pressure and peripheral resistance remaining depressed, while
heart rate, cardiac output, cardiac index, and stroke volume remained
elevated. Heart rate and arterial systolic pressure were also monitored in
conscious rats; rats in one group inhaled 500 ppm CO for 24 h, and rats in
a second group were injected with a bubble of pure CO ip. In both cases
heart rate was sharply elevated and blood pressure depressed as HbCO
saturation increased. Both parameters recovered on CO washout. There was no
significant difference between the response to inhaled vs. injected CO.
