Purpose: To present a case requiring regional anesthesia for both lower limbs, and to highlight the considerations to avoid potential local anesthetic toxicity, as a result of high cumulative doses of local anesthetic in this setting.
Clinical features: A 32-yr-old, obese (body mass index = 30.4 kg.m(-2)) woman required urgent, open reduction of bilateral ankle fractures. She also had facial, odontoid and pelvic fractures, and, in view of full stomach considerations, the anesthetic plan was to use regional anesthesia. Bilateral femoral and sciatic nerve blocks were performed, using a combination of ropivacaine and mepivacaine, with a 210-min interval between limbs. Blood samples were drawn 80 and 45 min after the first and second blocks, respectively, to measure plasma concentrations of the local anesthetics. Ropivacaine and mepivacaine concentrations were below reported toxic levels, and the patient underwent surgery successfully, without any symptoms suggestive of local anesthetic toxicity.
Conclusions: Regional anesthetic techniques for the lower limb may require local anesthetic doses approaching toxic levels, especially when bilateral blocks are required. This case indicates that by considering the pharmacokinetic and pharmacodynamic characteristics of each agent, and by timing the blocks properly to minimize peak plasma concentrations, the potential for local anesthetic toxicity can be reduced.