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) Cpmax was 1.45 (0.32) micrograms ml-1 and median (range) tCpmax was 25 (10-60) min. A concentration of 4.43 micrograms ml-1 measured in one patient was not associated with toxic signs. During continuous infusion of bupivacaine for 120 h, Cpmax was 4.9 (0.7) micrograms ml-1 and tCpmax 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.