Effect of Pre- and Postoperative Phenylbutazone and Morphine Administration on the Breathing Response to Skin Incision, Recovery Quality, Behavior, and Cardiorespiratory Variables in Horses Undergoing Fetlock Arthroscopy: A Pilot Study.
Authors: Conde Ruiz Clara, Cruz Benedetti Inga-Catalina, Guillebert Isabelle, Portier Karine Genevieve
Journal: Frontiers in veterinary science
Summary
# Editorial Summary Determining optimal timing for analgesic and anti-inflammatory medication in equine surgery remains clinically relevant, particularly when managing post-operative pain and maintaining cardiorespiratory stability during recovery. This randomised controlled pilot study assigned ten Standardbred horses undergoing fetlock arthroscopy to receive either morphine (0.1 mg/kg) and phenylbutazone (2.2 mg/kg) pre-operatively with saline post-operatively (PRE group), or the inverse protocol (POST group), while monitoring respiratory mechanics, blood gas values, recovery quality, and post-operative behaviour across a 48-hour period. Pre-operative dosing produced slightly elevated tidal volumes compared to post-operative administration during the pre-incision period (13 versus 9 mL/kg, p=0.01), yet this difference did not translate into clinically meaningful changes across other respiratory parameters, haemodynamic variables, or recovery scores, with skin incision itself producing no significant respiratory disturbance in either group. Neither timing of phenylbutazone and morphine administration influenced recovery quality as assessed by blinded evaluation, nor did it alter heart rate, respiratory rate, or the 25 behavioural demeanours recorded post-operatively through 48 hours. Whilst this small pilot study suggests timing of perioperative analgesia and NSAIDs may offer less practical consequence than previously theorised for routine fetlock arthroscopy, larger multicentre trials would be warranted before definitively reshaping clinical protocols around medication administration windows.
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Practical Takeaways
- •For fetlock arthroscopy under general anesthesia, the timing of morphine and phenylbutazone administration (before vs after induction) does not meaningfully affect recovery quality or postoperative comfort based on vital signs and behavior
- •Pre-operative administration of these analgesics and anti-inflammatories may provide slightly better ventilation during the pre-incision period, though clinical significance is unclear in this small study
- •Recovery planning for arthroscopic cases can be flexible regarding pain medication timing, as neither approach produced superior outcomes in this pilot study
Key Findings
- •Tidal volumes were significantly higher in the pre-operative drug administration group during the pre-incision period (13 vs 9 mL/kg, p=0.01)
- •Timing of morphine and phenylbutazone administration (pre- vs post-operative) did not significantly affect recovery quality, heart rate, respiratory rate, or postoperative behavior
- •Skin incision did not trigger measurable changes in respiratory variables in horses under isoflurane anesthesia
- •No significant differences in cardiorespiratory variables or dobutamine requirements between pre- and post-operative drug timing groups