Development of an Avian Brachial Plexus Nerve Block Technique for Perioperative Analgesia Using Mallard Ducks
Deena Brenner1,4, DVM; R. Scott Larsen1,2, DVM, MS, DACZM; Raymund F. Wack1,2, DVM, MS, DACZM; Peter J. Dickinson1,3, BVSc, PhD, DACVIM (Neurology); Peter Pascoe1,3, BVSc, PhD, DACVA, DECVA; D. Colette Williams1,3, BS
This investigation was conducted to develop a brachial plexus nerve block technique for perioperative analgesia in birds. Research on avian regional anesthesia is limited.2,4-6 A pilot study determined the feasibility of recording somatosensory evoked potentials (SSEP) for use in measuring the efficacy of the nerve blockade by testing the integrity of the brachial plexus.1,3 Eight adult female mallard ducks were anesthetized with isoflurane and used in several local anesthetic trials administering bupivacaine (2 mg/kg, 8 mg/kg) and lidocaine (15 mg/kg)/epinephrine (3.8 µg/kg) perineurally with a saline control treatment. Both dorsal and ventral approaches to the brachial plexus were evaluated, and a nerve stimulator was used to increase accuracy of administration. Sensory nerve conduction velocities (SNCV) for radial and ulnar nerves and cord dorsum potentials (CDP) were recorded prior to injection and at 5, 30, and 60 minutes post injection of local anesthetic or saline. For 24 h post injection, birds were intermittently monitored for the presence of a wing droop and decreased motor function. Surgical dissection and transection of the brachial plexus in one duck caused complete elimination of the CDP, which validated electrodiagnostic results.
Results were highly variable for all techniques. No technique consistently eliminated CDP or resulted in consistent wing droops. This may indicate that the treatment, dose, concentration, or volume of local anesthetic was ineffective in producing local analgesia. It is also possible that the methods used to assess loss of pain perception were not sensitive enough to assess the effects of the local anesthetic.
Funding for this research was provided by a grant from the Center for Companion Animal Health, University of California, Davis, Veterinary Medical Teaching Hospital.
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