We assessed possible pharmacokinetic modifications due to different epidural injection techniques using either a needle or a catheter. Adult patients (n=23) undergoing lower abdominal or lower extremity surgery were randomly assigned a single bupivacaine epidural injection anesthesia (0.5%, 15 mL, 0.3 mL/s) through needle or catheter device. Plasma bupivacaine concentration was quantified using a validated HPLC method and non-compartmental pharmacokinetic parameters estimated. CMAX and TMAX were similar in both groups: 952 ± 346 ng/mL, 0.65 ± 0.5 1h in the needle group; 810 ± 307 ng/mL, 0.43 ± 0.29 h in the catheter group respectively. Plasma AUC₀→∞ was also similar in both groups: 3868 ± 1687 ngh/mL for needle versus 4096 ± 1748 ngh/mL using catheter. The catheter group showed slower disposition than the needle group: t₁/₂=3.9 ± 2.3 h, MRT=6.0 ± 3.1 h versus 2.7 ± 1.03 h and 4.5 ± 1.2 h with needle administration respectively though it did not reach statistical significance, Cl/F and V/F were also similar. Lastly, female patients showed significant longer t1/2 after administration through catheter (5.7 ± 2.0 h) than needle (2.7 ± 0.6 h) group (P=0.0279). The device type does not affect the pharmacokinetics which is similar in both groups although sex-based differences might exist.
Keywords: Bupivacaine; Epidural anesthesia; Pharmacokinetics; Sex-based differences.
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