ED50 and ED95 of rocuronium during alfaxalone anesthesia in dogs

Abstract

Objective: To determine the median effective dose (ED₅₀) and effective dose required to depress the twitch value by 95% (ED₉₅) of rocuronium during alfaxalone anesthesia in dogs.

Study design: A randomized, prospective, crossover experimental study.

Animals: A total of eight adult Beagle dogs (four female, four male), weighing 10.3-14.6 kg and aged 6-8 years.

Methods: The dogs were anesthetized three times with 1.25-fold the individual minimum infusion rate of alfaxalone at intervals of ≥ 14 days. Neuromuscular function was monitored with train-of-four (TOF) stimulation of the peroneal nerve by acceleromyography. After recording the control TOF ratio (TOFRC) and first twitch of TOF (T1C), a single bolus dose of rocuronium 100, 175 or 250 μg kg^-1 (treatments R100, R175 or R250) was administered intravenously. The maximum suppression of the first twitch of TOF (T1) was recorded and calibrated with T1C to construct the dose-response curve, from which ED₅₀ and ED₉₅ were calculated. Time from rocuronium administration to TOF ratio/TOFRC > 0.9 (duration TOFR0.9) was recorded.

Results: ED₅₀ and ED₉₅ of rocuronium during alfaxalone anesthesia were 175 and 232 μg kg^-1, respectively. The median (range) duration TOFR0.9 was longer in treatment R250 [10.1 (9.2-10.9) minutes] than in treatments R100 [3.1 (2.9-4.4) minutes; p < 0.0001] and R175 [7.7 (6.9-8.1) minutes; p < 0.0001]; and longer in treatment R175 than in treatment R100 (p < 0.0001).

Conclusions and clinical relevance: The duration of TOFR0.9 correlated positively with the dosage of rocuronium, indicating that recovery time of rocuronium was also dose-dependent in dogs anesthetized with alfaxalone. The duration TOFR0.9 of rocuronium 250 μg kg^-1 was 10 minutes during alfaxalone anesthesia in dogs.

Keywords: administration and dosage; alfaxalone; dose–response relationship; drug; prospective studies; veterinary.