Assessment of halothane and sevoflurane anesthesia in spontaneously breathing rats.
OBJECTIVE
To characterize halothane and sevoflurane anesthesia in spontaneously breathing rats.


METHODS
16 healthy male Sprague-Dawley rats.


METHODS
8 rats were anesthetized with halothane and 8 with sevoflurane. Minimum alveolar concentration (MAC) was determined. Variables were recorded at anesthetic concentrations of 0.8, 1.0, 1.25, and 1.5 times the MAC of halothane and 1.0, 1.25, 1.5, and 1.75 times the MAC of sevoflurane.


RESULTS
Mean (+/- SEM) MAC for halothane was 1.02 +/- 0.02% and for sevoflurane was 2.99 +/- 0.19%. As sevoflurane dose increased from 1.0 to 1.75 MAC, mean arterial pressure (MAP) decreased from 103.1 +/- 5.3 to 67.9 +/- 4.6 mm Hg, and PaCO2 increased from 58.8 +/- 3.1 to 92.2 +/- 9.2 mm Hg. As halothane dose increased from 0.8 to 1.5 MAC, MAP decreased from 99 +/- 6.2 to 69.8 +/- 4.5 mm Hg, and PaCO2 increased from 59.1 +/- 2.1 to 75.9 +/- 5.2 mm Hg. Respiratory rate decreased in a dose-dependent fashion from 88.5 +/- 4.5 to 58.5 +/- 2.7 breaths/min during halothane anesthesia and from 42.3 +/- 1.8 to 30.5 +/- 4.5 breaths/min during sevoflurane anesthesia. Both groups of rats had an increase in eyelid and pupillary aperture with an increase in anesthetic dose.


CONCLUSIONS
An increase in PaCO2 and a decrease in MAP are clinical indicators of an increasing halothane and sevoflurane dose in unstimulated spontaneously breathing rats. Increases in eyelid aperture and pupil diameter are reliable signs of increasing depth of halothane and sevoflurane anesthesia. Decreasing respiratory rate is a clinical indicator of an increasing dose of halothane.
Steffey
Michele A
MA
Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
Brosnan
Robert J
RJ
Steffey
Eugene P
EP
D000769:Anesthesia, Inhalation / Q000662:veterinary*; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D000830:Animals, Laboratory; D001784:Blood Gas Analysis; D001794:Blood Pressure / Q000187:drug effects; D006221:Halothane / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D008738:Methyl Ethers / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012119:Respiration / Q000187:drug effects*; D000077149:Sevoflurane
D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D006221:Halothane