THE MINIMUM ALVEOLAR CONCENTRATION OF SEVOFLURANE IN RATS

There are only limited data on sevoflurane minimum alveolar concentrat ion (MAC) in rats. This study was designed to determine the minimum al veolar concentration value for sevoflurane in younger and older rats. Minimum alveolar concentration determination was performed in spontane ously breathing animals, 9-week-old rats (younger, n=8) and more than 13-month-old rats (older, n=8). Rats were instrumented with a silastic catheter in the abdominal aorta via the femoral artery to allow for a rterial blood gas sampling. Subsequently, minimum alveolar concentrati on for sevoflurane was determined in 40 younger and 38 older rats. Min imum alveolar concentration for sevoflurane in younger rats was signif icantly higher than in the older rats (2.68 +/- 0.19 vs. 2.29 +/- 0.19 , P<0.001). Subgroup analysis indicated that minimum alveolar concentr ation for sevoflurane was not affected by the presence of an arterial catheter in the abdominal aorta (younger, 2.75 +/- 0.08 vs. 2.67 +/- 0 .21; older, 2.23 +/- 0.19 vs. 2.30 +/- 0.18). Minimum alveolar concent ration is profoundly affected by the age of the animal, but not by lim ited instrumentation.