The disposition of bupivacaine following a 72 h interpleural infusion in cholecystectomy patients.
The disposition of bupivacaine and degree of analgesia following a 72 h interpleural infusion was investigated in 12 adult patients undergoing elective cholecystectomy. The infusion regimen of an initial interpleural bolus dose of 20 ml of 0.5% bupivacaine HCl with adrenaline (1:200,000) followed by continuous infusion at a rate of 8 ml h-1 of 0.25% plain bupivacaine HCl was designed to achieve continuous post-operative pain relief for 72 h. In practice an additional bolus dose (identical to the first) administered 5 h after infusion commencement was required to achieve adequate pain relief on the first postoperative day. The mean measured steady-state plasma bupivacaine concentration was 2.1 mg l-1 (s.d. +/- 0.54, range 1.3-3.2 mg l-1). Disposition parameters for bupivacaine measured for the infusion were calculated by non-compartmental methods and compared with previous values obtained after single and multiple interpleural bolus dose administration. No statistically significant differences were noted and, in particular, the systemic clearance of bupivacaine (mean 10.2 l h-1 s.d +/- 3.0; range 6.3-16.0 1 h-1) remained unchanged following the long-term interpleural infusion. Analgesia was deemed satisfactory throughout the entire post-operative period.