Effect of systemic lidocaine on visceral and somatic nociception in conscious horses
Article first published online: 5 JAN 2010
2005 EVJ Ltd
Equine Veterinary Journal
Volume 37, Issue 2, pages 122–127, March 2005
How to Cite
ROBERTSON, S. A., SANCHEZ, L. C., MERRITT, A. M. and DOHERTY, T. J. (2005), Effect of systemic lidocaine on visceral and somatic nociception in conscious horses. Equine Veterinary Journal, 37: 122–127. doi: 10.2746/0425164054223723
- Issue published online: 5 JAN 2010
- Article first published online: 5 JAN 2010
- Paper received for publication 17.05.04; Accepted 18.08.04
- systemic lidocaine;
Reasons for performing study: Commonly used analgesics (nonsteroidal anti-inflammatory agents, opioids and α2-agonists) have unwanted side effects. An effective alternative with minimal adverse effects would benefit clinical equine pain management.
Objectives: To compare the effect of lidocaine or saline on duodenal and rectal distension threshold pressure and somatic thermal threshold in conscious mature horses.
Hypothesis: Systemically administered lidocaine would increase somatic and visceral nociceptive thresholds.
Methods: Lidocaine (2 mg/kg bwt bolus followed by 50 μg/kg bwt/min for 2 h) or saline was administered to 6 horses each carrying a permanently implanted gastric cannula, in a randomised, blinded cross-over design. Thermal threshold was measured using a probe containing a heater element placed over the withers which supplied heat until the horse responded. A barostatically controlled intraduodenal balloon was distended until a discomfort response was obtained. A rectal balloon was inflated until extruded or signs of discomfort noted.
Results: Thermal threshold was increased significantly 30 and 90 mins after the start of lidocaine infusion. There was no change in duodenal distension pressure and a small but clinically insignificant change in colorectal distension pressure in the lidocaine group.
Conclusions: At the dose used, systemically administered lidocaine produced thermal antinociception but minimal changes in visceral nociception.
Potential relevance: At these doses, lidocaine may play a role in somatic analgesia in horses.