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Effect of systemic lidocaine on visceral and somatic nociception in conscious horses
Author(s) -
ROBERTSON S. A.,
SANCHEZ L. C.,
MERRITT A. M.,
DOHERTY T. J.
Publication year - 2005
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.2746/0425164054223723
Subject(s) - lidocaine , medicine , anesthesia , nociception , saline , cannula , bolus (digestion) , distension , adverse effect , horse , surgery , paleontology , receptor , biology
Summary Reasons for performing study : Commonly used analgesics (nonsteroidal anti‐inflammatory agents, opioids and α 2 ‐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.