The effect of dobutamine and bolus crystalloid fluids on the cardiovascular function of isoflurane-anaesthetised horses.

This research investigates the impact of dobutamine and a bolus of crystalloid fluids on the cardiovascular capacities of anaesthetised horses. The results indicate that the combination of the two may have a positive effect on muscle compared to using dobutamine alone.

Keywords and Concepts Explained

• Dobutamine: A medication often employed in veterinary and human medicine to increase the heart’s output.
• Crystalloid fluids: Solutions that contain small molecules that can easily flow across semipermeable membranes; they’re widely employed in intravenous therapy to treat dehydration or electrolyte imbalances.
• Acepromazine: A common sedative administered prior to anesthesia in veterinary medicine.
• Isoflurane: An anesthetic used in both human and veterinary medicine.
• Cardiac Index (CI): An indicator used to evaluate the heart’s pumping efficacy.

Research Method

• A randomized, cross-over experiment was employed, which means the animals received both treatments in random order and acted as their controls.
• 6 horses, aged 5-13 years and weighing 464-578 kg, were part of the sample group.
• These horses were sedated using a mix of acepromazine, xylazine, ketamine, and diazepam, then anaesthetised with isoflurane.

Treatment

• The horses were administered two treatments.
• In the first, dubbed treatment D, dobutamine infusion was started and adjusted to hit a target mean arterial pressure (MAP).
• In the second treatment, D+F, the horses received the same dobutamine administration as in the first treatment but also received a bolus of Hartmann’s solution, a type of crystalloid fluid.
• Several parameters, including cardiac index, haemoglobin concentration, arterial oxygen content, oxygen delivery index and bilateral femoral arterial blood flow, were monitored at three timepoints: at the start, 30 minutes after the beginning of the dobutamine infusion, and 15 minutes after dobutamine was stopped.

Findings

• Treatment D resulted in increased oxygen delivery index, hemoglobin concentration, and arterial oxygen content.
• Treatment D+F significantly increased femoral arterial blood flow in both the upper and lower limbs.
• There were considerable differences between the two treatments in terms of the monitored parameters at the second and third timepoints.
• There was no change in Cardiac Index during either treatment.

Conclusions

• The co-administration of fluids and dobutamine – as in treatment D+F – seemed to increase femoral arterial blood flow, suggesting that it could be beneficial for the muscle compared to administering dobutamine alone.