Effects of adenosine infusion on the minimum alveolar concentration of isoflurane in dogs.
OBJECTIVE
To determine the effects of adenosine infusion on the minimum alveolar concentration (MAC) of isoflurane in dogs.


METHODS
Prospective, randomized crossover study.


METHODS
Seven adult male and female Beagles weighing 10.9 (7.5, 13.6) kg [median (minimum, maximum)].


METHODS
Each dog was anesthetized with isoflurane in oxygen and randomly assigned to receive either an intravenous (IV) adenosine (0.3 mg kg(-1) minute(-1)) or saline (6 mL kg(-1) hour(-1) IV) infusion. After an interval of 7 days or more, each dog was re-anesthetized and treated with the alternative infusion. Using a tail-clamp technique, MAC was determined before (pre-infusion), during (infusion), and 2 hours after the infusions (post-infusion).


RESULTS
The pre-infusion MAC of isoflurane was 1.25 (1.15, 1.35) [median (minimum, maximum)] vol.% for the saline treatment group and 1.25 (1.05, 1.45) vol.% for the adenosine treatment group, and did not differ significantly between the two treatments. The infusion MAC values were not significantly different (p = 0.16) and were 1.25 (0.95, 1.35) vol.% and 1.05 (1.00, 1.25) vol.%, respectively. The post-infusion MAC values differed significantly (p = 0.016); MAC was 1.15 (1.15, 1.35) vol.% and 1.05 (1.05, 1.25) vol.% for the saline and adenosine treatment groups, respectively. During infusion, mean arterial blood pressure decreased significantly (p = 0.008) during adenosine treatment compared with the saline 66 mmHg (52, 72) and 91 mmHg (68, 110), respectively. End-tidal CO2 (Pe'CO2), urine production, hematocrit, and plasma total solids did not differ significantly between the two treatments at any time (all p > 0.05).


CONCLUSIONS
Although the MAC of isoflurane in dogs was not decreased significantly during infusion with adenosine (0.3 mg kg(-1) minute(-1)), it was significantly decreased post-infusion, but only by 0.1 vol.%, an amount not considered clinically important. Adenosine infusion decreased mean arterial pressure by 27% and did not adversely affect renal function.
Asakawa
Makoto
M
Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA. ma273@cornell.edu
Ludders
John W
JW
Badgley
Britton L
BL
Erb
Hollis N
HN
Gleed
Robin D
RD
Posner
Lysa P
LP
D000241:Adenosine / Q000008:administration & dosage* / Q000494:pharmacology*; D018685:Anesthetics, Inhalation / Q000493:pharmacokinetics*; D000818:Animals; D001794:Blood Pressure; D004285:Dogs; D004347:Drug Interactions; D005260:Female; D006339:Heart Rate; D007262:Infusions, Intravenous / Q000662:veterinary; D007530:Isoflurane / Q000493:pharmacokinetics*; D008297:Male; D011650:Pulmonary Alveoli / Q000187:drug effects* / Q000378:metabolism*
D018685:Anesthetics, Inhalation; D007530:Isoflurane; D000241:Adenosine