Continuous peripheral neural blockade to alleviate signs of experimentally induced severe forelimb pain in horses

Ashlee E. Watts, DVM, DACVS; Alan J. Nixon, BVSc, MS, DACVS; Heidi L. Reesink, VMD; Jonathan Cheetham, VetMB, PhD, DACVS; Susan L. Fubini, DVM, DACVS; Andrea L. Looney, DVM, DACVA
April 15, 2011
Journal of the American Veterinary Medical Association

Objective—To investigate the efficacy and safety of a low-volume, single-catheter, continuous peripheral neural blockade (CPNB) technique to locally deliver bupivacaine to alleviate signs of severe forelimb pain resulting from experimentally induced tendonitis in horses. Design—Randomized controlled experimental trial. Sample—14 horses and 5 forelimbs from equine cadavers. Procedures—Horses underwent collagenase-induced superficial digital flexor tendonitis in the midmetacarpal region of 1 forelimb. To deliver analgesia, a closed-tip catheter was placed from lateral to medial, approximately 12 cm distal to the accessory carpal bone, between the suspensory ligament and accessory ligament of the deep digital flexor tendon. Success of catheter placement and anesthetic delivery was documented ex vivo in 5 forelimbs from equine cadavers. Effective analgesia in affected forelimbs of horses from continuous (n = 7) versus intermittent (7) local anesthetic delivery (intermittent peripheral neural blockade; IPNB) was compared over a 3-day period. Results—Horses that received CPNB in the affected forelimb were less lame than horses that received IPNB. A lower proportion of CPNB-treated horses had behavioral and physiologic signs of pain, compared with IPNB-treated horses. Neither technique completely blocked the sensation of pain or resulted in swelling in the distal portion of the forelimb, vasodilation, or an increase in lameness. After removal, Staphylococcus aureus was cultured from 1 catheter tip. Conclusions and Clinical Relevance—For short-term treatment, CPNB was more effective than IPNB for reduction in signs of severe pain in the distal aspect of the forelimb of horses.