A preliminary study on the effects of atropine sulphate on bradycardia and heart blocks during romifidine sedation in the horse.

The research investigated the effects of Atropine Sulphate on bradycardia and heart blocks in horses that occur as a result of sedation using Romifidine, a newly developed sedative. It was found that Atropine Sulphate effectively counteracted these cardiovascular disturbances, without altering the effectiveness of the sedative or causing any notable side effects.

Methodology

• The exploratory study was conducted on nine warm-blood horses who were arbitrarily split into three groups.
• Each group was administered different dosages of Romifidine – 0.04, 0.08, and 0.12 mg/kg of body weight – through intravenous means, with a minimum seven-day gap between tests.
• In addition to Romifidine, the horses were also given a placebo (NaCl 0.9%) injected 5 minutes before and after the sedative, along with a small dose of Atropine Sulphate (0.005 mg/kg of body weight) also injected 5 minutes prior to administering Romifidine.

Findings

• It was observed that regardless of the dosage, Romifidine resulted in significant bradycardia, AV block, and some sinus blocks.
• The presence of the placebo did not influence the cardiac abnormalities caused by Romifidine.
• If administered prior to the sedative, Atropine Sulphate, even in low doses, effectively combated the bradycardia and brought about an average to increase in heart rhythm across all Romifidine dosages.
• A higher dose of Atropine Sulphate, injected 5 minutes before sedation, triggered tachycardia (average 70 beats/minute) at all Romifidine levels and completely stopped both the bradycardia and the heart blocks.
• Increasing the doses of Romifidine slightly reduced the chronotropic effects of Atropine Sulphate.

Conclusions

• Administering Atropine Sulphate, either in low or high doses, five minutes after Romifidine led to its effects being seen after about 5 minutes.
• Irrespective of the exact dosage, Atropine Sulphate effectively interrupted the bradycardia and nullified the heart blocks.
• There were no observed side-effects of Atropine in the horses that were not fasted.
• The sedative functioning of Romifidine was not impacted in any way because of the use of Atropine Sulphate, irrespective of whether it was given before or after the sedative.