Concentration-dependent bupivacaine myotoxicity in rabbit extraocular muscle

Cheng Zhang, Pittaya Phamonvaechavan, Anand Rajan, David Y. Poon, Pinar Topcu-Yilmaz, David L. Guyton

Research output: Contribution to journalArticle

22 Scopus citations

Abstract

Purpose: Bupivacaine myotoxicity to the extraocular muscles, from retrobulbar or peribulbar anesthesia, has been reported after cataract surgery and other intraocular procedures. However, there are no data on the concentration-dependence of bupivacaine in causing extraocular muscle toxicity. Methods: Six aged rabbits received different concentrations of bupivacaine (0.75% and lower) in 3 extraocular muscles, namely, superior rectus, inferior rectus, and inferior oblique muscles of each rabbit's eye. The animals were euthanized at 5 days or 1 month after the injections. Hematoxylin and eosin- and Masson trichrome-stained sections were obtained from the involved extraocular muscles after paraffin embedding. Results: Five days after the initial injection, the 0.75% bupivacaine-injected extraocular muscles showed extensive myonecrosis and degeneration with early-stage regenerating muscle fibers. However, muscle tissue injected with half-concentration bupivacaine (0.38%) showed scattered and significantly fewer areas of mild muscle fiber degeneration with regeneration. There were no areas of muscle tissue degeneration observed in any muscle injected with quarter-concentration bupivacaine (0.19%). At 1 month, however, only 0.75% bupivacaine-injected muscles displayed areas of regenerated muscle fiber cells with foci of scar formation. There was no visible scar formation in muscles injected with any bupivacaine concentration lower than 0.75%, or with saline, at 1 month after injection. Conclusions: Extraocular muscle injection with full-strength bupivacaine (0.75%) can cause myonecrosis and degeneration acutely, with regeneration appearing by 5 days, followed by some late-stage scar formation. However, no long-term effects were observed with bupivacaine concentrations of 0.38% or 0.19%.

Original languageEnglish (US)
Pages (from-to)323-327
Number of pages5
JournalJournal of AAPOS
Volume14
Issue number4
DOIs
StatePublished - Aug 1 2010
Externally publishedYes

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health
  • Ophthalmology

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    Zhang, C., Phamonvaechavan, P., Rajan, A., Poon, D. Y., Topcu-Yilmaz, P., & Guyton, D. L. (2010). Concentration-dependent bupivacaine myotoxicity in rabbit extraocular muscle. Journal of AAPOS, 14(4), 323-327. https://doi.org/10.1016/j.jaapos.2010.05.009