Clinical Use of a Multivariate Electroencephalogram (Narcotrend) for Assessment of Anesthetic Depth in Horses during Isoflurane-Xylazine Anesthesia.
Authors: Tünsmeyer Julia, Hopster Klaus, Kästner Sabine B
Journal: Frontiers in veterinary science
Summary
# Editorial Summary Assessing anesthetic depth in horses remains challenging during routine procedures, and the Narcotrend EEG monitor—widely used in human and small animal anaesthesia—offered potential as an objective alternative to clinical observation. Researchers tested whether Narcotrend index (NI) values would reliably correlate with isoflurane depth across seven horses anaesthetised with xylazine infusion and isoflurane maintenance, recording EEG data at eight different end-tidal isoflurane concentrations (0.8–2.2 vol%) and simultaneously scoring clinical signs of anaesthetic depth on a four-point scale. The Narcotrend index showed poor correlation with isoflurane concentration (rs = 0.24), fluctuating only between 13 and 48 across all horses, whereas traditional clinical scoring demonstrated strong inverse correlation (rs = 0.80) with increasing isoflurane levels. For equine practitioners relying on xylazine-balanced isoflurane anaesthesia, these findings suggest that Narcotrend monitoring does not provide clinically useful depth assessment in horses, and conventional observation of reflexes, muscle tone and respiratory patterns remains the most reliable—and currently the only validated—method for titrating anaesthetic planes during routine procedures.
Read the full abstract on PubMed
Practical Takeaways
- •Do not rely on Narcotrend EEG monitoring for assessing anesthetic depth in horses under isoflurane-xylazine anesthesia; traditional clinical observation remains superior
- •Clinical signs (eye position, pupil size, muscle tone, reflex responses) remain the gold standard for monitoring anesthetic plane in equine practice
- •Equipment designed for human or other species may not translate reliably to equine patients and should be validated before clinical adoption
Key Findings
- •Narcotrend index showed poor correlation (rs = 0.24) with end-tidal isoflurane concentrations in horses
- •Clinical scoring of anesthetic depth demonstrated strong correlation (rs = 0.80) with increasing isoflurane concentrations
- •Narcotrend index values ranged only 13-48 across all horses, limiting clinical utility for depth discrimination
- •Narcotrend EEG monitor was not useful for assessing anesthetic depth in horses receiving isoflurane-xylazine anesthesia