Recovery from anaesthesia in ponies: a comparative study of the effects of isoflurane, enflurane, methoxyflurane and halothane.

This research evaluates the duration and quality of recovery from anaesthesia in ponies, and finds isoflurane to be the most satisfactory anaesthetic due to its shorter recovery time and smoother transition to standing.

Study Design

• The study was structured to compare the effects of four different volatile anaesthetic agents on experimental ponies: isoflurane, enflurane, halothane, and methoxyflurane.
• Each pony underwent separate 2-hour anaesthetic periods with each of the individual agents, equating to a total of four anaesthetic sessions per animal.

Findings

• The fastest recovery from anaesthesia was recorded after administering isoflurane, followed by enflurane, halothane, and methoxyflurane.
• Despite this, the act of standing post-anaesthesia was achieved more rapidly with enflurane in comparison to isoflurane.
• The order of recovery times was found to be compatible with the inherent solubilities of the four anaesthetic agents in question.

Quality of Recovery

• The smoothest recovery was observed after anaesthesia with isoflurane. This was followed by methoxyflurane, halothane, and finally enflurane.
• An isoflurane recovery was marked by extended periods of quiet sternal recumbency (lying on the chest), and excellent coordination when the ponies got up to stand.
• Particular difficulties with halothane recovery included shivering and delayed coordination upon standing.
• Recovery from enflurane featured a very brief period of sternal recumbency but there was significant shivering and incoordination once the ponies attempted to stand. This was theorized to be potentially due to residual excitatory effects from central nervous stimulation during anaesthesia.

Conclusion

• Based on the duration and quality of recovery periods observed, the study concluded that isoflurane was the most suitable volatile anaesthetic for use in horses.