Isoflurane does not depress the hypoxic response of rabbit carotid body chemoreceptors.

Abstract

Whether volatile anesthetics have an effect on the peripheral chemoreceptors is controversial, possibly because of differences in end-tidal CO(2) concentrations. We studied the effect of isoflurane on the hypoxic chemosensitivity of carotid body chemoreceptors at three different PaCO(2) levels before and during the administration of 1.0% isoflurane (0.5 minimum alveolar anesthetic concentration) in six normothermic New Zealand white rabbits anesthetized with thiopental. The response of the chemoreceptors was fitted to the equation: Frequency (Hz) = a + b x PaCO(2) + c x (1/PaO(2)) + Dx (1/PaO(2))(2). Mean values for the coefficients a, b, c and d for the control state were -4.5, 0.13, 771, and 6332, respectively. This relationship was not changed by addition of isoflurane at 1.0% end-tidal concentration (P = 0.40, analysis of variance). We conclude that isoflurane at 1.0% end-tidal concentration does not depress the hypoxic response of rabbit carotid body chemoreceptors during either hypo-, normo-, or hypercapnia. By measuring single-fiber chemoreceptor activity in anesthetized rabbits, we showed that isoflurane at 1.0% end-tidal concentration does not depress the hypoxic chemosensitivity of peripheral chemoreceptors during either hypo-, normo-, or hypercapnia in this species.