PLASMA-CONCENTRATIONS OF BUPIVACAINE AND ITS ENANTIOMERS DURING CONTINUOUS EXTRAPLEURAL INTERCOSTAL NERVE BLOCK

Plasma concentrations of bupivacaine have been measured in 12 patients given bupivacaine through a paravertebral catheter placed under direct vision at thoracotomy. After an initial bolus of 0.5% bupivacaine 20 ml, mean (SEM) C(P)max was 1.45 (0.32) mug ml-1 and median (range) tC(P)max was 25 (10-60) min. A concentration of 4.43 mug ml-1 measured in one patient was not associated with toxic signs. During continuous infusion of bupivacaine for 120 h, C(P)max was 4.9 (0.7) mug ml-1 and tC(P)max 48 (5-96) h. No symptoms or signs of toxicity occurred. Separate measurement of R- and S-bupivacaine concentrations demonstrated significantly different concentration-time profiles.