Photobiomodulation therapy using a class 3b laser does not cause premature rupture of multivesicular liposomal bupivacaine suspensions in a cadaver model

Objective: To determine if photobiomodulation causes a premature release of liposomal bupivacaine (LB) suspensions.

Animals: A 25-kg mixed breed dog cadaver euthanized for reasons unrelated to this study.

Methods: In September 2022, a proximomedial tibial incision was made in a dog cadaver, and a tibial plateau leveling osteotomy plate was implanted. A stab incision was made one-half inch distal to the incision, and a tunnel to the plate was created prior to closure of the primary wound. A 3-cc anal sac catheter was advanced through the distal incision until the bulb rested against the face of the plate. Seven treatment groups of treatment power (watts) and total energy (joules/cm2) were defined as: A, 0.5 W, 2.0 J/cm2; B, 0.5 W, 4.0 J/cm2; C, 0.5 W, 6.0 J/cm2; D, 1.0 W, 2.0 J/cm2; E, 1.0 W, 4.0 J/cm2; F, 1.0 W, 6.0 J/cm2; and sham, 0.0 W, 0.0 J/cm2. Ten samples per group of 2 mL of LB were infused into a new catheter and treated percutaneously with a class 3b laser. All samples remained in the catheter for 12 seconds to reflect the longest treatment time. Post-treatment free bupivacaine concentrations were identified with high-performance liquid chromatography.

Results: The median free bupivacaine concentration was reported as: sham, 1.89 mg/mL; A, 1.93 mg/mL; B, 2.01 mg/mL; C, 2.05 mg/mL; D, 1.92 mg/mL; E, 2.03 mg/mL; and F, 2.00 mg/mL. There were no differences in median free bupivacaine concentrations between groups (P = .988).

Clinical relevance: Concurrent LB and photobiomodulation are recommended during the postoperative period. The results of this proof-of-concept study suggest that concurrent use of LB and photobiomodulation may be safe, but in vivo studies at similar and stronger photobiomodulation settings are warranted.