Neuromuscular and cardiovascular effects of atracurium in ponies anesthetized with halothane.

The research evaluates the effects of a neuromuscular-blocking agent, Atracurium besylate, on halothane-anesthetized ponies. It focuses on the dosage required for surgical relaxation, observation of the paralysis phase, recovery phase, cardiovascular side effects, and the impact of edrophonium on the reversal of Atracurium effects.

Experiment and Dosing

• The study involved 15 ponies anesthetized with halothane and then given Atracurium besylate to induce surgical relaxation, which is defined as a 95% to 99% reduction in hoof twitch.
• Every pony received 3 injections with 8 among them receiving 2 additional ones.
• An initial 0.11 +/- 0.01 mg/kg dosage of Atracurium besylate produced desired relaxation, and all subsequent dosages were 0.052 mg/kg.

Analysis of Paralysis and Recovery Phases

• The paralysis phase (from maximum twitch reduction to 10% twitch recovery) lasted around 24 +/- 5 minutes for the initial injection.
• The paralysis phase from subsequent doses was slightly shorter.
• The recovery phase was observed from the fall of twitch recovery from 10% to 75% and lasted approximately 11 minutes, remaining consistent for initial and repeated injections.

Side Effects and Reversal

• The experiment found no observable cardiovascular side effects from the use of Atracurium.
• The researchers used edrophonium for reversing the effects of Atracurium. A successful reversal was achieved when the evoked digital extensor tension (a twitch indicator) returned to 95% of the baseline after the last Atracurium dosage.
• Edrophonium, however, influenced the blood pressure and heart rate. The systolic blood pressure increased to 121% +/- 7% of the baseline. The heart rate altered to 93% +/- 9% of the baseline after the introduction of edrophonium.

Recovery to Standing

• Overall, the recovery to standing was smooth and strong. Most ponies stood within 30 minutes to an hour after transportation to the recovery stall, showcasing a good tolerance level to the administered anesthetics.