Minimum alveolar concentration of isoflurane in dogs administered a single intramuscular injection of racemic or S (+)-ketamine after premedication with acepromazine-morphine

Concentração alveolar mínima do isoflurano em cães tratados com dose única intramuscular de cetamina racêmica ou S (+) após premedicação com acepromazina-morfina

ABSTRACT:

The present study evaluated the minimum alveolar concentration of isoflurane (ISO_MAC) in twenty three dogs premedicated with acepromazine (0.02mgkg^-1) and morphine (0.5mgkg^-1) and administered racemic (RK) or S(+)-ketamine (SK). Dogs randomly received a single dose (3mgkg^-1, IM) of either RK or SK 15minutes after anesthetic induction with propofol. The ISO_MAC was determined by the up-and-down method. Approximately 20 minutes after administration of RK or SK, a surgical noxious stimulus was applied and the response evaluated. The ISO_MAC was 0.50±0.01% in the RK group (n=10) and 0.31±0.04% in the SK group (n=13). The ISO_MAC was 38% lower in the SK group compared to the RK group. Results of the present study revealed that in dogs premedicated with acepromazine and morphine, IM administration of 3mgkg^-1 ketamine approximately 20 minutes before the noxious stimulus produced clinically important reduction in the ISO_MAC and the MAC-sparing effect was significantly greater with SK compared to RK.

Key words:
dissociative anesthesia; MAC; NMDA antagonist; phencyclidine derivative; preemptive analgesia