Minimum alveolar concentration of isoflurane in mechanically ventilated Dumeril monitors.
OBJECTIVE
To determine minimum alveolar concentration (MAC) of isoflurane in mechanically ventilated Dumeril monitors (Varanus dumerili).


METHODS
Prospective study.


METHODS
10 healthy adult Dumeril monitors.


METHODS
Anesthesia was induced with isoflurane in oxygen delivered through a face mask. Monitors were endotracheally intubated, and end-tidal and inspired isoflurane concentrations were continuously measured. After equilibration at an end-tidal-to-inspired isoflurane concentration ratio of >0.9 for 20 minutes, an electrical stimulus (50 Hz, 50 V) was delivered to the ventral aspect of the tail for up to 1 minute and the monitor was observed for purposeful movement. End-tidal isoflurane concentration was then decreased by 10%, and equilibration and stimulation were repeated. The MAC was calculated as the mean of the lowest end-tidal isoflurane concentration that prevented positive response and the highest concentration that allowed response. A blood sample for blood gas analysis was collected from the tail vein at the beginning and end of the anesthetic period.


RESULTS
Mean +/- SD MAC of isoflurane was 1.54 +/- 0.17%. Mean heart rates at the upper and lower MAC values were 32.4 +/- 3 beats/min and 34 +/- 4.5 beats/min, respectively. During the experiment, PaCo2 decreased significantly from 43.1 mm Hg to 279 mm Hg and blood pH and HCO3 concentration increased significantly from 7.33 to 7.64 and from 25.3 to 32.9 mmol/L, respectively.


CONCLUSIONS
The MAC of isoflurane in Dumeril monitors was similar to that reported in mammals but lower than values reported in other reptiles. This difference may be reflective of the more advanced cardiovascular physiologic features of monitor lizards.
Bertelsen
Mads F
MF
Toronto Zoo, 361A Old Finch Ave, Scarborough, ON M1B 5K7, Canada.
Mosley
Craig A E
CA
Crawshaw
Graham J
GJ
Dyson
Doris
D
Smith
Dale A
DA
D018685:Anesthetics, Inhalation / Q000592:standards*; D000818:Animals; D001784:Blood Gas Analysis / Q000662:veterinary; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D007530:Isoflurane / Q000592:standards*; D008116:Lizards / Q000378:metabolism* / Q000502:physiology; D008297:Male; D010313:Partial Pressure; D011446:Prospective Studies; D011650:Pulmonary Alveoli / Q000378:metabolism*; D012121:Respiration, Artificial / Q000662:veterinary
D018685:Anesthetics, Inhalation; D007530:Isoflurane