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Extended Sensory Blockade Using Hydrogel Encapsulated Bupivacaine
Steven Alexander Hanna, MD1; Tommy Nai-Jen Chang, MD1,2; Mike Cooke, B.Sc, PhD3; Daniel Demsey, B.Sc, MD1; Jessica Ngai, B.Sc3; Jennifer Zhang, B.Sc, MD, PhD1; Molly Lindway, MD3; Tessa Gordon, PhD1; Molly Shoichet, PhD3; Gregory H. Borschel, MD3
1The Hospital for Sick Children, Toronto, ON, Canada, 2Department of Plastic and Reconstructive Surgery, Chang Gung Memorial Hospital, Chang Gung Medical College and Chang Gung University, Taoyuan, Taiwan, 3The University of Toronto, Toronto, ON, Canada
Introduction: Nerve blocks or wound infiltration with local anesthetics relieve postsurgical pain for a few hours but a longer duration is needed. Given the side effects and dependency associated with opioid use, a reduction in their use would be beneficial. Extending the duration of action of local anesthetics could aid in this endeavor. Using a rat sciatic nerve block model, we investigated the efficacy of a novel hydrogel combined with bupivacaine.
Methods: Rats received an injection of either a control bupivacaine solution or hydrogel encapsulated bupivacaine around the sciatic nerve. Assessment of the nerve block included the Von Frey monofilament test, a noxious pinch test, and cold plantar assay.
Results: In a sample of 62 male Sprague Dawley rats, the hydrogel encapsulated bupivacaine resulted in a significantly (p<0.001) longer nerve block of 21.4 ± 4.4 hours as measured by the Von Frey test; this block lasted13 times the duration of the control nerve block. The hydrogel encapsulated bupivacaine also yielded a significantly longer nerve block as measured by the noxious pinch test (p<0.001) and cold plantar assay (p<0.01).
Conclusion: This hydrogel encapsulated bupivacaine yields a significantly longer nerve block than bupivacaine alone. We suspect that this formulation may greatly extend the duration regional anesthesia in humans. Given the potential morbidities associated with opiate use and the fact that pain is the primary reason for readmission after any type of surgical procedure, our findings may have major clinical implications.
Mean Nerve Block Duration – Von Frey
Mean Nerve Block Duration – Pinch Test
Mean Nerve Block Duration – Cold Plantar Assay
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