PHARMACOKINETIC PROFILE OF EPIDURALLY INJECTED BUPIVACAINE IN AWAKE PATIENTS

In order to investigate the influence of general anaesthesia on the ph armacokinetics of bupivacaine 0.5% after a single, epidurally injected dose of 20ml (= 100mg), 5 patients, scheduled for surgical procedures appropriate for epidural anaesthesia without the need for combination with general anaesthesia, were studied. In all patients an arterial, central venous and intrathecal catheter were inserted for sampling of, respectively, arterial and central venous blood and cerebrospinal flu id (CSF), at regular intervals up to 12 hours after administration. Bu pivacaine was analysed by gas chromatography. The drug appeared after 2 minutes in the plasma and CSF samples, and was still detectable afte r 12 hours. There were no significant differences between the bupivaca ine concentrations in the arterial and central venous plasma samples a t all times. The same applied for the calculated plasma pharmacokineti c parameters at all intervals. The bupivacaine concentrations in the C SF were many dozen times higher than in the plasma samples at all time s. There was no clear evidence of a pulmonary retention of bupivacaine in this study. From a pharmacokinetic point of view the epidural anae sthesia was largely spinal anaesthesia.