Journal of Applied Physiology, Vol 63, Issue 4 1351-1359, Copyright © 1987 by American Physiological Society
Cardiopulmonary function during 7 h of constant-dose halothane and methoxyflurane
E. P. Steffey, T. B. Farver and M. J. Woliner
Department of Surgery, School of Veterinary Medicine, University of California, Davis 95616.
Cardiopulmonary effects of prolonged, constant-alveolar-dose halothane
(HAL) and methoxyflurane (MOF) in O2 anesthesia on spontaneously breathing
dogs were determined. One hour after anesthetic induction, end-tidal
concentration was set at 1.04% HAL or 0.28% MOF [each representing 1.2
minimum alveolar concentration (MAC) for dogs] and maintained for 7 h. No
time-related changes were associated with MOF. However, HAL significantly
(P less than 0.05) elevated cardiac output (Q) from 2 to 7 h by increasing
stroke volume; mean aortic pressure (MAP) also increased with time (P less
than 0.05 beginning at 5 h). Four of these dogs were studied again at least
3 wk later at a constant end-tidal dose of 1.48% HAL in O2 (1.7 MAC). Q and
MAP were lower initially during 1.7 MAC than during 1.2 MAC but not after 2
h of anesthesia. The greater HAL dose initially depressed ventilation and
elevated arterial partial pressure of CO2 (PaCO2) compared with the lower
dose. PaCO2 continued to increase with duration of 1.7 MAC HAL, as did
results of ventilatory gas volume and flow measurements.
