Background
The present study was designed to test the hypothesis that high-dose dexmedetomidine added to local anesthetic would increase the duration of sensory and motor blockade in a rat model of sciatic nerve blockade without causing nerve damage.

Perineural Administration of Dexmedetomidine in Combination with Bupivacaine Enhances Sensory and Motor Blockade in Sciatic Nerve Block without Inducing Neurotoxicity in Rat

https://rapm.bmj.com/content/rapm/29/4/333.full.pdf

Local anesthetic myotoxicity.

Corticosteroids and local anesthetics have significant variability in their formulations that may increase their adverse event profile for specific procedures.

https://pubs.rsna.org/doi/pdf/10.1148/radiol.2523081929

Injectable corticosteroid and local anesthetic preparations: a review for radiologists.

• Postoperative diplopia and ptosis can be temporary or permanent complications in patients who have undergone ophthalmic surgery while under local anesthesia. We encountered six patients with such complications and hypothesize that some cases of postoperative diplopia and ptosis could be attributed to myotoxic effects of local anesthetics. These effects may cause the degeneration and subsequent regeneration of muscle fibers of the levator or extraocular muscles and result in temporary or permanent muscle weakness.

Postoperative diplopia and ptosis. A clinical hypothesis based on the myotoxicity of local anesthetics.

Twelve thousand regional anaesthetics for cataract extraction and intraocular lens implantation surgery were administered by one anaesthetist over a period of 52 months in a free-standing outpatient surgicalfacility. The ophthalmologist, who did all the operations, assessed the qualify of the blocks using an objective scoring system which is described. The first 3,595 patients had retrobulbar and seventh nerve blocks. The following 1,640 patients had higher volume retrobulbar blocking alone. The next 3,478 had peribulbar blocks, followed by 2,226 who had a modifiedform of peribulbar blocking. A final group of 1,061 had a combination of peribulbar and periorbital blocks with added retrobulbar injection if indicated. As the method of blocking evolved, the more closely was the goal of safe, painless and effective regional anaesthesia approached. The requirements for effective anaesthesia of this type are presented, the complications described and the importance of familiarity with the anatomy of the orbit and its contents stressed.

/pdf/regional-anaesthesia-for-12-000-cataract-extraction-and-58ndppwmm8.pdf

Regional anaesthesia for 12,000 cataract extraction and intraocular lens implantation procedures

Myotoxic effects of 2% lidocaine with 1:100,000 epinephrine were evaluated in rats and humans. Sprague-Dawley rats were give injections in the left gastrocnemius muscle of 0.5 ml of the lidocaine preparation or a control vehicle; they were killed in groups of four at 0, 8, 24, and 48 hours. Blood samples were taken for serum enzyme determinations, and muscle specimens were removed and processed for histologic evaluation. In eight patients undergoing radical neck dissection, 1.8 ml of lidocaine with epinephrine or its control was injected into the sternocleidomastoid muscle approximately 18 hours before surgery. Patients' muscle specimens obtained at surgery were handled similarly to those of the rat. Serum creatine kinase, aspartate aminotransferase, and alanine aminotransferase activities were markedly elevated in the rat at 8 hours in the experimental group, but not in the control group. Histologically, control injections elicited no damage in the rat other than a mild inflammatory reaction along the presumptive needle track. Lidocaine with epinephrine, however, destroyed most of the muscle in which it was injected. Myonecrosis was qualitatively similar in humans. The rat provides a good model for the study of local anesthetic-induced myonecrosis.

Ralph D. Buoncristiani

Papers

Comparison of myotoxic effects of lidocaine with epinephrine in rats and humans.