Evaluation of lidocaine for brachial plexus blockade in eastern box turtles (Terrapene carolina carolina).

Objective: To evaluate latency and duration of a brachial plexus block technique in eastern box turtles performed with 2% lidocaine at three dose rates.

Study Design: Prospective, randomized, blinded crossover study.

Animals: Adult eastern box turtles, two for drug dose evaluation and a group of six (three male, three female) weighing 432 ± 40 g (mean ± standard deviation) for the main study.

Methods: Animals were randomly assigned to four brachial plexus blocks with lidocaine at 5, 10 and 20 mg kg or 0.9% saline (treatments LID5, LID10, LID20 and CON, respectively), separated by 1 week. Treatment side was randomized and blocks were performed unilaterally. Baseline observations of mentation, heart rate (HR), respiratory rate (f), skin temperature and limb response to manipulation or toe pinch were evaluated. Assessments were made every 10 minutes until 1 hour of normal sensory and motor function to the treated thoracic limb, or for a total of 2 hours if no block was evident.

Results: Motor and sensory blockade was achieved in treatments LID10 and LID20 in one turtle, with a latency of 10 minutes and duration of 50 minutes for both doses. Raising of the ipsilateral lower palpebra occurred with both blocks. Turtles administered lidocaine experienced higher HR compared with CON, and HR decreased over time for all individuals. Mentation and f were not changed with any lidocaine dose.

Conclusions: The technique was unreliable in producing brachial plexus motor and sensory blockade at the lidocaine doses evaluated in this study. HR was higher in lidocaine-administered turtles but remained within normal limits for the species. No change in mentation or f was observed among treatments.

Clinical Relevance: General anesthesia with systemic analgesia is recommended for surgical procedures involving the chelonian thoracic limb. Further studies are needed to optimize a brachial plexus block in this species.