Plasma Concentrations of Lidocaine Associated with Axillary Brachial Plexus Block

Park, Hye Suk; Baek, Woon Yi; Hong, Jung Gil; Park, Jin Woong; Kim, Byung Kwon

Abstract

Brachial plexus block, axillary approach appears to be a safe and reliable technique for upper extremity surgery from shoulder to hand. However, the maximum dose of lidocaine that is recommended by the manufactured is 4 mg per kg (approximately 300 mg) regardless of the injection site. The maximum recommended dose for lidocaine with epinephrine is 7 mg per kg (approximately 500 mg). These maximum recommended amounts are insufficient for brachial plexus block. We question the logic behind these recommended dosages and may exceed them. The aim of this study was to determine whether commonly acceptable dosages used in brachial plexus block within a safe range. The time courses of the plasma concentration were observed in 20 healthy patients to whom were axillary injected with 1.5% lidocaine mixed 1: 200,000 epinephrine. The plasma concentrations were measured by immunofluororesence assay at the intervals of 5, 10, 20, 30 and 60 minutes. The values of plasma concentration were 2.65+/-75, 4.29+/-2.75, 5.95 +/-2.02, 4.76+/-1.91 and 4.48+/-1.90 pg/ml in group 1, and 3.71+/-1.68, 4.76+/-1.91, 6.68+/-3.43, 5.57+/-3.08 and 5.56+/-2.86 ug/ml in group 2, and 2.86+/-1.82, 5.08+/-3.74, 5.92+/-3.84, 6.82+/-3.84 and 5.49+/-3.29 ug/ml in group 3 (Mean+SD). The peak plasma concentration was 5.95+/-2.02 and 6.68+/-3.43 ug/ml at 20 minutes in group 1 and 2 respectively and 6.82+/-3.84 ug/ml at 30 minutes in group 3. These results indicated that the lidocaine 750 mg with epinephrine (5 ug/ml) in brachial plexus block is considered to be safe because plasma concentration dose not exceed the toxic level.