Liposomal bupivacaine does not prolong neuraxial blockade and produces less consistent motor blockade than bupivacaine hydrochloride in inland bearded dragons (Pogona vitticeps)

Objective: To compare the effects of liposomal bupivacaine (LB) to standard bupivacaine hydrochloride (B) formulation following neuraxial injection in inland bearded dragons (Pogona vitticeps). Methods: 12 adult bearded dragons (0.35 ± 0.13 kg) were sedated with alfaxalone (15 mg/kg SC), and neuraxial injections were performed with B treatment (1.5 mg/kg to 0.3 mL/kg) and LB treatment (4 mg/kg to 0.3 mL/kg) in all animals in a randomized, crossover, blinded experimental design with a 7-day interval. Motor/sensory block was assessed by mechanical stimulation of limbs; 25%, 50%, and 75% of the trunk's length; and cloacal vent tone. Heart rate, respiratory rate, righting reflex, and head position were evaluated. Results: Overall success was 100% for B treatment and 92% for LB treatment. Median onset was 5 minutes for both B and LB treatments. Duration and extent of blockade were similar between treatments; however, pelvic limb motor blockade was less consistent in the LB treatment (7 of 12 animals), with 3 animals showing unilateral blockade. Apnea requiring manual ventilation occurred in 2 animals in the B treatment and in 2 animals in the LB treatment. Conclusions: Bupivacaine hydrochloride at 1.5 mg/kg (0.3 mL/kg) produced reliable motor and sensory blockade but resulted in respiratory complications. Liposomal bupivacaine at 4 mg/kg (0.3 mL/kg) resulted in a similar onset, extent and duration of blockade but less consistent motor blockade and was also associated with respiratory complications. Clinical Relevance: Neuraxial injection continues to show promise as a regional anesthetic technique in healthy bearded dragons, providing extensive motor and sensory blockade. However, respiratory complications occurred with both bupivacaine formulations at the doses evaluated, indicating that lower doses should be used. Further studies are needed to establish the safety profile and clinical advantages of lipossomal bupivacaine before clinical use.