Medetomidine continuous rate intravenous infusion in horses in which surgical anaesthesia is maintained with isoflurane and intravenous infusions of lidocaine and ketamine.

This research sought to assess the effectiveness of medetomidine as part of a continuous intravenous infusion for anaesthetizing horses. The anaesthesia was supported by isoflurane with further continuous infusions of lidocaine and ketamine. The study found that adding medetomidine did decrease the necessary isoflurane concentration to maintain effective surgical anaesthesia and also reduced the amount of dobutamine required to sustain mean arterial pressure.

Methodology

• The study worked off of the data gathered from forty horses that underwent elective surgery. The animals were randomized and blinded which helped maintain the study’s reliability and integrity.
• The anaesthesia procedure consisted of sedation and induction followed by maintenance with isoflurane and mechanical ventilation.
• All horses received lidocaine (1.5 mg kg(-1) initially, then reduced to 2 mg kg(-1) hr(-1)) and ketamine (2 mg kg(-1) hr(-1)), both dropped to 1.5 mg kg(-1) hr(-1) after 50 minutes.
• One group of horses, known as the MILK group, received an additional continuous infusion of medetomidine along with the other drugs while the second group, known as the ILK group, was given saline instead. Both infusions reduced their dosage after 50 minutes.

Results

• It was found that the concentration of isoflurane, vital for maintaining surgical anaesthesia, decreased steadily over time in the MILK group, becoming significantly less than that in the ILK group after 45 minutes.
• Apart from this, medetomidine also decreased the amount of dobutamine required to maintain mean arterial pressure, indicating a potential cost saving for surgeries.
• Recovery times were similar for both groups and the recovery quality was rated as good.

Conclusions

• The researchers concluded that the addition of a CRI of medetomidine along with lidocaine and ketamine led to a reduction in the concentration of isoflurane necessary to maintain an adequate level of anaesthesia.
• Furthermore, the use of this combination also required less dobutamine to maintain MAP.
• The study also deduced that no additional sedation was required for a calm recovery, which could potentially reduce the overall costs and invasiveness of surgeries.