Medetomidine-ketamine anaesthesia induction followed by medetomidine-propofol in ponies: infusion rates and cardiopulmonary side effects.
Authors: Bettschart-Wolfensberger R, Bowen I M, Freeman S L, Weller R, Clarke K W
Journal: Equine veterinary journal
Summary
# Editorial Summary Researchers investigating total intravenous anaesthesia (TIVA) as an alternative to inhalation anaesthesia in equines examined a medetomidine-ketamine induction protocol followed by four hours of medetomidine-propofol maintenance in six ponies, measuring cardiopulmonary stability and anaesthetic quality throughout. Induction proved smooth and reliable, with propofol infusion rates ranging from 0.89–0.1 mg/kg/min during maintenance, whilst all cardiovascular and respiratory parameters remained remarkably stable over the four-hour period—mean arterial pressure holding at 90.0–120.8 mmHg, cardiac index between 44.1–59.8 ml/kg/min, and respiratory rate 13.0–15.8 breaths/min on spontaneous ventilation with high oxygen supplementation. Recovery to standing averaged 31.1 minutes with minimal struggling (one or two attempts), and critically, no clinically significant hypoxaemia developed despite one pony recording a concerning post-operative arterial oxygen level of 8.5 kPa after four hours. This protocol offers equine anaesthetists a viable TIVA alternative to volatile agents—particularly valuable given that total intravenous techniques eliminate the need for expensive inhalation equipment and may reduce perioperative mortality in horses—though the borderline oxygenation in one subject warrants continued vigilance with extended procedures and suggests that individual monitoring remains essential even with seemingly robust protocols.
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Practical Takeaways
- •This medetomidine-ketamine-propofol protocol offers a viable injectable alternative to inhalation anaesthesia for equine procedures up to 4 hours, potentially reducing fatality risks associated with volatile anaesthetics
- •The technique demonstrates cardiovascular stability and smooth recovery, making it suitable for field or clinical use where inhalation equipment may not be available
- •Monitor PaO2 closely during extended procedures despite high oxygen supplementation, as hypoxaemia may develop; ensure adequate ventilation support capability
Key Findings
- •Medetomidine-ketamine induction followed by medetomidine-propofol infusion provided excellent anaesthesia induction with gentle movements after pain stimuli in 6 ponies undergoing 4-hour procedures
- •Mean propofol infusion rates ranged from 0.89-0.1 mg/kg bwt/min with no cardiopulmonary changes over the 4-hour period
- •Cardiovascular function remained remarkably stable with heart rate 31.2-40.8 beats/min and mean arterial pressure 90.0-120.8 mmHg throughout anaesthesia
- •Recovery to standing averaged 31.1 minutes with ponies standing within one or two attempts despite minimal PaO2 of 8.5 kPa in one pony after 4 hours despite FIO2 >0.9