Late hyaluronidase injection in local anesthesia: Morphofunctional evaluation in rat sciatic nerve block

• Main Authors: Anna Carolina Ratto Tempestini-Horliana, Marcelo Lazzaron Lamers, Maurício Yonamine, Patricia Verónica Aulestia-Viera, Marinilce Fagundes Dos Santos, Maria Aparecida Borsatti
• Format: Article
• Language: English
• Published: Wolters Kluwer Medknow Publications 2019-01-01
• Series: Indian Journal of Dental Research
• Subjects: anesthesia adjuvants; anesthetics; hyaluronic acid; hyaluronoglucosaminidase
• Online Access: http://www.ijdr.in/article.asp?issn=0970-9290;year=2019;volume=30;issue=5;spage=692;epage=696;aulast=Tempestini-Horliana
• ISSN: 0970-9290; 1998-3603

Introduction: 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.