Tempestini-Horliana, Anna Carolina RattoLamers, Marcelo LazzaronYonamine, MaurícioAulestia-Viera, Patricia VerónicaSantos, Marinilce Fagundes DosBorsatti, Maria Aparecida2020-01-022020-01-022019-09Tempestini-Horliana Anna Carolina Ratto, Lamers Marcelo Lazzaron, Yonamine Maurício, Aulestia-Viera Patricia Verónica, Santos Marinilce Fagundes Dos, Borsatti Maria Aparecida . Late hyaluronidase injection in local anesthesia: Morphofunctional evaluation in rat sciatic nerve block. Indian Journal of Dental Research. 2019 Sep; 30(5): 692-6960970-92901998-3603http://imsear.searo.who.int/handle/123456789/192300Introduction: Despite the enhancing effects of hyaluronidase (HYAL) over duration of anesthesia, this enzyme could cause adverse effects when injected concomitantly with local anesthetics in dental blocks. Objective: This study aimed to assess the tissue alterations caused by a local anesthetic protocol consisting of a late HYAL injection and confirm its functional effectiveness. Materials and Methods: The protocol efficacy was proved by evaluating sensory and motor functions in rats. The sciatic nerve was blocked with 2% lidocaine (LID) with epinephrine (n = 25). Thirty minutes later, 75 TRU/ml HYAL was injected into the same site (experimental group, LID/HYAL). One week later, this protocol was repeated in the contralateral hindlimb, injecting only HYAL's vehicle (control group, LID/vehicle [LID/V]). To observe the integrity of the local tissues, histological specimens were obtained 1, 24, 48, and 72 h after treatment with LID/HYAL or LID/V (n = 16 each) and stained with hematoxylin/eosin and picrosirius red. Results: Local inflammation was similar in both groups. The integrity of the nerve fibers was preserved, in spite of some inflammation-associated injuries in the surrounding tissues. The reversible tissue disorganization caused by HYAL, probably facilitated the diffusion of the residual anesthetic to the nerve, resulting in a prolonged anesthetic effect (P < 0.05). Conclusions: No irreversible morphological alterations are caused by the administration of HYAL prior the end of the LID-induced block. Moreover, this protocol prolongs LID's anesthetic effect.Anesthesia adjuvantsanestheticshyaluronic acidhyaluronoglucosaminidaseJournal ArticleIndiaBiophotonics Program, School of Dentistry, University Nove De Julho, São Paulo, BrazilDepartment of Morphological Sciences, Federal University of Rio Grande Do Sul, Institute of Health Science, Porto Alegre, BrazilDepartment of Clinical and Toxicological Analysis, Faculty of Pharmaceutics Sciences, University of São Paulo, Cidade Universitária, São Paulo, BrazilDepartment of Stomatology, School of Dentistry, University of São Paulo, Cidade Universitária, São Paulo, BrazilDepartment of Cell and Developmental Biology, University of São Paulo, Institute of Biomedical Sciences, Cidade Universitária, São Paulo, Brazil