Effect of systemic lidocaine on visceral and somatic nociception in conscious horses.

Summary

# Editorial Summary: Systemic Lidocaine for Equine Analgesia Robertson and colleagues investigated whether intravenous lidocaine might offer a viable alternative to conventional analgesics (NSAIDs, opioids and alpha-2 agonists), which carry significant side effects in horses. Six horses received either lidocaine (2 mg/kg bolus followed by 50 µg/kg/min infusion for 2 hours) or saline in a blinded, randomised cross-over design, with nociceptive thresholds assessed via thermal stimulation over the withers and barostatic distension of duodenal and rectal balloons. Thermal threshold increased significantly at 30 and 90 minutes post-infusion, but duodenal distension pressure showed no meaningful change, whilst rectal distension pressure increased only marginally and clinically insignificantly. For equine practitioners seeking multimodal analgesia options—particularly for somatic pain—systemic lidocaine appears promising at these doses, though its limited effect on visceral nociception means it is unlikely to serve as a standalone agent for colic or other visceral conditions; integration into combination protocols warrants further investigation.

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Key Findings

• •Systemic lidocaine (2 mg/kg bolus + 50 µg/kg/min infusion) significantly increased thermal threshold at 30 and 90 minutes post-infusion in conscious horses
• •Duodenal distension pressure showed no significant change with lidocaine administration
• •Rectal distension pressure showed only small, clinically insignificant changes in the lidocaine group
• •Lidocaine produced somatic thermal antinociception but minimal visceral antinociceptive effects at the doses studied

Conditions Studied