Plasma bupivacaine concentrations during postoperative continuous epidural analgesia.

Postoperative analgesia and plasma concentrations of bupivacaine were evaluated in six patients receiving intermittent epidural bupivacaine for a period of 72 hours following large bowel surgery. Repeated doses were administered every hour by a new automatic, specially designed pump. Venous plasma bupivacaine concentrations showed accumulation for up to 48-60 hours during administration and were mostly less than 2 micrograms/ml except in an elderly, frail patient in whom a peak of 3.9 micrograms/ml was observed. This convenient, low-dose, pulsed technique provided excellent analgesia although special care may be necessary in the elderly and frail patient if potentially toxic levels are to be avoided.