Effect of adrenaline on venous plasma concentrations of bupivacaine after interpleural administration.

Bupivacaine 2.5 mg kg-1 (0.5 ml kg-1 of 0.5% solution), with or without adrenaline 5 micrograms ml-1, was administered by interpleural injection to 12 patients after elective cholecystectomy. Noncompartmental analysis indicated that the addition of adrenaline had no effect on total body clearance, apparent volume of distribution at steady state or elimination half-life of bupivacaine. However, peak plasma concentrations were lower in the adrenaline group (mean (SD) [range]: 2.57 (0.61) [1.52-3.11] vs 3.22 (0.27) [2.84-3.53] micrograms ml-1, P less than 0.05) and the time to maximum concentration was delayed (median [range]: 25 [15-30] vs 15 [10-20] min, P less than 0.05). Analgesia was variable and no differences were detected between the two groups. The addition of adrenaline appears prudent to minimize possible bupivacaine toxicity.