Bupivacaine toxicity secondary to continuous cervical epidural infusion. Case report.

BACKGROUND AND OBJECTIVES A case is described of bupivacaine toxicity after continuous cervical epidural infusion in a patient with intractable cancer pain. The patient had several periods of generalized tonic clonic seizures. Serial venous blood samples were taken after the first signs of toxicity. The highest total plasma bupivacaine level was 20.3 micrograms/mL. The corresponding free bupivacaine concentration was not determined. The highest measured free bupivacaine concentration was 1.21 micrograms/mL, corresponding with a total plasma bupivacaine level of 6.7 micrograms/mL. There were no signs of cardiovascular toxicity. The patient recovered after treatment without adverse sequelae. METHODS A plasma concentration-time curve was constructed. There was a rise in the plasma concentration of bupivacaine after the continuous infusion was stopped. RESULTS Total body clearance of bupivacaine was 20 mL/min and elimination half-life was 27 hours. CONCLUSIONS The case emphasizes the importance of serial plasma concentrations of bupivacaine after continuous epidural infusion and the value of free bupivacaine concentration versus total bupivacaine concentration.