The stress response to anaesthesia in ponies: barbiturate anaesthesia.

The research article examines the stress responses in horses during anesthesia, specifically by comparing the effects of halothane and barbiturate anesthetics in ponies. The study suggests that barbiturates may induce less of a stress response than halothane in horses, but notes that recovery after 2 hours of barbiturate-induced anesthesia was poor, limiting its practical use.

Research Methodology

• The researchers conducted tests on nine ponies in order to measure their stress response to two different anesthetic drugs: thiopentone and pentobarbitone, both types of barbiturates.
• In one session, six ponies were anesthetized using thiopentone, and no additional drugs were administered. These ponies were able to stand up within 30 minutes.
• In another session, the six original ponies plus three additional ones were anesthetized using pentobarbitone, and the anaesthesia was sustained for two hours. No surgeries were performed during either of these sessions.

Measurements and Findings

• The team monitored several factors before, during, and after anaesthesia. These included plasma concentrations of glucose, lactate, non-esterified fatty acids, cortisol, insulin, catecholamines, and adrenocorticotrophic hormone.
• The researchers observed no significant changes in the horses’ hormones or metabolites during either anaesthetic session, and the animals remained normotensive, i.e., their blood pressure remained within normal ranges.
• These results contrasted significantly with earlier findings from the same ponies, which experienced substantial stress responses and hypotension (low blood pressure) when anesthetized with halothane.
• However, the researchers also discovered that recovery from pentobarbitone anaesthesia was poor after two hours, making this type of anaesthetic impractical for clinical use.

Conclusion and Future Research

• The paper concludes that while barbiturates appear to induce less of a stress response in equine anaesthesia than halothane, the poor recovery rates following prolonged pentobarbitone anaesthesia preclude its widespread use in clinical settings.
• The researchers suggest the need for further exploration of non-cumulative intravenous agents or non-hypotensive volatile agents for use in equine anaesthesia to strike the balance between mitigating stress responses and ensuring reasonable recovery times.