Effect of Fentanyl Infusion on Heart Rate Variability and Anaesthetic Requirements in Isoflurane-Anaesthetized Horses.
Authors: Dmitrović Petra, Vanaga Jana, Dupont Julien, Franck Thierry, Gougnard Alexandra, Detilleux Johann, Kovalcuka Liga, Salciccia Alexandra, Serteyn Didier, Sandersen Charlotte
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Low-dose fentanyl infusion during equine general anaesthesia has generated considerable debate, with inconsistent evidence regarding its clinical utility. This blinded prospective study of 22 horses compared standard isoflurane anaesthesia supplemented with either fentanyl (6 µg/kg loading dose followed by 0.1 µg/kg/min infusion; n=11) or saline placebo (n=11), measuring isoflurane requirements, cardiovascular stability, and parasympathetic tone activity (PTA) as a marker of anaesthetic depth. Whilst fentanyl provided no reduction in isoflurane consumption or requirement for dobutamine support, horses receiving the opioid needed significantly less ketamine for anaesthetic maintenance, and demonstrated higher PTA values indicative of greater parasympathetic activity. Although these findings suggest fentanyl may offer modest adjunctive benefits in maintaining stable anaesthetic depth without cardiovascular compromise, the clinical significance of improved PTA monitoring remains unclear, and practitioners should exercise caution in extrapolating results until larger studies clarify whether these effects translate to meaningful improvements in recovery quality or reduced anaesthetic complications in routine equine surgery.
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Practical Takeaways
- •Low-dose fentanyl infusion may reduce supplementary ketamine requirements during isoflurane anaesthesia in horses, potentially decreasing total drug exposure
- •While fentanyl did not spare isoflurane requirements, it appears to enhance parasympathetic tone, which may provide cardiovascular benefits during general anaesthesia
- •Fentanyl CRI can be safely incorporated into equine anaesthetic protocols without necessitating reductions in primary anaesthetic agent dosing
Key Findings
- •Low-dose fentanyl CRI (0.1 µg/kg/min) did not significantly reduce isoflurane requirements in anaesthetized horses
- •Fentanyl group required significantly lower ketamine doses to maintain adequate anaesthetic depth
- •Horses receiving fentanyl showed significantly higher parasympathetic tone activity (PTA) values
- •Mean fentanyl plasma concentration achieved was 6.2 ± 0.83 ng/mL with no differences in MAP or dobutamine requirements between groups