Local anaesthetic-induced myotoxicity in regional anaesthesia: a systematic review and empirical analysis

Abstract

Recent reports of local-anaesthetic (LA)-induced myotoxicity after peripheral nerve blocks have increased the interest in this less commonly known complication. Basic science evidence investigating LA-induced myotoxicity seems to demonstrate a pattern, but findings from human studies vary. This systematic review summarises the existing myotoxicity evidence and empirically examines its implications. Databases were searched for all in vitro animal and human studies evaluating LA-induced myotoxicity. Studies were stratified by design. Data sought included the model examined, LA used, injury mechanisms, nature of damage, and extent of recovery. For human studies, we also aimed to estimate prevalence and recovery rates. One hundred and fifteen studies, mainly animal and ophthalmic, were included. Myotoxicity risk factors included higher concentrations and prolonged exposure to LA, and use of bupivacaine. Injury mechanisms involved early and late aberrations to cytoplasmic calcium (Ca) homeostasis by the sarcoplasmic reticulum Ca ATPase. Incidence in ophthalmic studies was 0.77% (392 of 50 618). Inflammatory changes within a few days after exposure marked the onset of myotoxicity, and myo-degeneration followed within the first week post-exposure. Time to recovery in human muscles ranged between 4 days to 1 yr. None/partial and complete recovery were observed in 61% and 38% of patients, respectively. Across all experimental models, skeletal muscles exposed to LA consistently display myotoxic effects. Evidence is robust in animal and ophthalmic studies, and displays a concerning signal with continuous adductor canal block use in human case reports. Exploring the clinical prevalence, severity, and risk-reducing strategies of myotoxicity should be prioritised.

Randomized controlled trial of a simplified adductor canal block performed for analgesia following total knee arthroplasty

“…Myotoxicity is known to occur after local anesthetic injection, and in vitro data suggest this effect is concentration-dependent 16. Most adverse clinical effects have occurred after retrobulbar block, although rare cases of myotoxicity are reported after interscalene and trigger point injections 16.…”

“…Most adverse clinical effects have occurred after retrobulbar block, although rare cases of myotoxicity are reported after interscalene and trigger point injections 16. Increased toxicity associated with bupivacaine has been suggested as a motivation for using ropivacaine when performing ACB.…”

Local Anesthetics

“…Recovery time in human muscles ranged from 4 days to 1 year. None partial and complete recovery was observed in 61% and 38% of patients, respectively [61]. All LAs that have been studied have a similar myotoxic potential in terms of the tissue alterations produced, but they differ in the intensity of these lesions.…”

Ultrasound-guided upper and lower extremity nerve blocks in children

“…Recent findings in adults showed an increased risk for myotoxicity for continuous adductor canal block; hence, the risks and benefits for perineural catheter in this space should be equally and carefully balanced in children. 16 Whilst evidence is still lacking in children, studies in adults have confirmed that the SN block at the level of the adductor canal offers a similar analgesic profile to the FN block for knee surgery while preserving quadriceps strength. 17,18 Obturator nerve block…”