Case report: ropivacaine neurotoxicity at clinical doses in interscalene brachial plexus block.

Purpose: To describe a case of ropivacaine toxicity following an ultrasound guided interscalene block and discuss the possible mechanisms involved.

Clinical Features: A 76-yr-old woman with multiple myeloma was scheduled for open reduction and internal fixation following a pathological fracture of her left upper humerus. She developed central nervous system toxicity with ropivacaine 15 min after a carefully placed ultrasound-guided interscalene catheter. The dose of ropivacaine was within recommended limits and there was no evidence that the catheter was intravascular. Surgery proceeded uneventfully under general anesthesia. The interscalene catheter was left in situ for postoperative evaluation and intravascular injection was ruled out with a colour Doppler study. The total ropivacaine plasma concentration was 3.68 microgxmL-(1). Neurological evaluation, contrast computerized tomography and electroencephalogram were normal. The patient was discharged home with no sequelae. Advanced age, malnutrition, epinephrine and possible elevation of alpha-(1)-acid glycoprotein levels could have altered the pharmacokinetics of plasma ropivacaine and possibly contributed to delayed neurotoxicity.

Conclusions: Local anesthetic toxicity is an uncommon but well documented complication of regional anesthesia. Careful monitoring and preparedness for managing complications during the conduct of regional anesthesia cannot be overemphasized. Experience from this case suggests that local anesthesia toxicity can happen within safe dose limits and without intravascular placement despite careful attention to needle and catheter placement, fractionated dosing and frequent aspirations.