Minimum anesthetic concentration of isoflurane and sparing effect of midazolam in Quaker parrots (Myiopsitta monachus)

Abstract

ObjectiveTo determine the effects of midazolam on the minimum anesthetic concentration (MAC) reduction of end-tidal isoflurane concentration (Fe′Iso) measured using an electrical stimulus in Quaker parrots (Myiopsitta monachus). Study designRandomized crossover experimental study. AnimalsA group of six adult Quaker parrots, weighing 98–124 g. MethodsBirds were anesthetized with isoflurane in oxygen delivered by mask, then tracheally intubated and mechanically ventilated. Three treatments were applied with a 4 day interval between anesthetic events. Each anesthetized bird was administered midazolam (1 mg kg−1; treatment MID1), midazolam (2 mg kg−1; treatment MID2) or electrolyte solution (control) intramuscularly. The treatments were administered using a replicated Latin square design and the observers were blinded. Based on a pilot bird, the starting Fe′Iso was 1.8%. After equilibration for 10 minutes, a supramaximal stimulus was delivered using an electrical current (20 V and 50 Hz for 10 ms) and birds were observed for non-reflex movement. The Fe′Iso was titrated by 0.1% until a crossover event was observed. The MAC was estimated using logistic regression. ResultsThe MAC of isoflurane (MACISO) was estimated at 2.52% [95% confidence interval (CI), 2.19–2.85] with a range of 1.85–2.65%. MACISO in MID1 was 2.04% (95% CI, 1.71–2.37) and in MID2 was 1.81% (95% CI, 1.48–2.14); reductions in MACISO from control of 19% (p = 0.001) and 28% (p < 0.001), respectively. Heart rate, temperature, sex and anesthetic time were not different among treatments. ConclusionsMidazolam (1–2 mg kg−1) intramuscularly resulted in a significant isoflurane-sparing effect in response to a noxious stimulus in Quaker parrots without observable adverse effects. Clinical relevanceMidazolam can be used as part of a balanced anesthetic approach using isoflurane in Quaker parrots, and potentially in other psittacine species.