Effect of low-dose atropine administration on dobutamine dose requirement in horses anesthetized with detomidine and halothane.

The study investigates the possibility of reducing the need for supportive cardiovascular treatment in horses that are anesthetized with detomidine and halothane, using a low dose of atropine. The research indicated that intravenous atropine administration resulted in improved blood pressure, requiring less dobutamine, without observing any complications associated with higher atropine doses.

Research Methodology

• The researchers divided the animals into three groups of 10 healthy horses each.
• All 30 horses were given detomidine according to their body weight.
• The first group received intravenous atropine an hour after detomidine administration, the second group received intramuscular atropine at the time of detomidine administration, while the horses in the third group didn’t receive any atropine and served as a control group.
• Various physiological parameters such as heart rate, mean arterial blood pressure, systemic blood pressures, end-tidal halothane, end-tidal CO2 and arterial blood gas tensions were measured before and during the study at fixed intervals.
• The researchers also adjusted the dobutamine infusion rate for maintaining mean arterial blood pressure between 70 and 80 mm of Hg.

Research Findings

• The researchers observed that the heart rates were higher in horses that received atropine either intravenously or intramuscularly compared to the control group’s horses.
• The systemic arterial pressure in horses receiving intravenous atropine was higher. These horses also required a lower dobutamine infusion rate compared to the other groups.
• Interestingly, the commonly-observed complications, such as colic and dysrhythmias, from use of higher doses of atropine were not seen when a low dose was administered.

Conclusions

• The study concluded that, amongst halothane-anesthetized horses treated with detomidine, the group given a low dose of atropine intravenously required less dobutamine compared to the intramuscular and no-atropine-received groups.
• This indicates that the intravenous administration of a low dose of atropine prior to inducing general anesthesia could improve blood pressure regulation in horses pre-treated with detomidine before halothane anesthesia.