Comparison of Plasma Concentrations of Levobupivacaine With and Without Epinephrine for Transversus Abdominis Plane Block

Background and Objectives: The pharmacokinetics for levobupivacaine in transversus abdominis plane (TAP) blocks has not been previously reported. We aimed to determine the extent of the block and the effect on plasma concentrations of levobupivacaine with the addition of epinephrine. Methods: We enrolled 11 healthy volunteers in this double-blind, 2-intervention, 2-period crossover study. The intervention periods were defined as a unilateral left TAP block with 20 mL of 0.25% levobupivacaine with (E) or without (no E) 5 mu g/mL epinephrine. Subjects were randomized to E, followed by no E or no E followed by E, with 2-week washout period. Sensory dermatomal anesthesia was recorded. Blood samples were obtained for the measurement of plasma levobupivacaine levels. Results: The median cranial-to-caudal spread of sensory blockade for sharp touch was T9 (interquartile range [IQR], T7-T10) to L1 (IQR, T12-L1) with epinephrine and T9 (IQR, T8-T10) to T12 (IQR, T11-L1) without epinephrine (P > 0.05). The mean maximum arterial levobupivacaine concentrations with epinephrine were 0.36 (95% bootstrap confidence interval [95% CI], 0.30-0.42) mu g/mL and 0.63 (95% CI, 0.49-0.85) mu g/mL without epinephrine (P = 0.014, difference in means of 0.27 [95% CI, 0.12-0.46]). The mean maximal venous levobupivacaine concentration was 0.32 (95% CI, 0.28-0.39) mu g/mL and 0.49 (95% CI, 0.37-0.68) mu g/mL, with and without epinephrine, respectively (P = 0.006, difference in means of 0.17 [95% CI, 0.08-0.33]). The mean duration of the blockade was 10.2 hours (95% CI, 8.5-12.5 hours) with epinephrine and 10.3 hours (95% CI, 8.7-12.4 hours) without epinephrine (P = 1.000). Conclusions: Adding epinephrine to levobupivacaine reduces its peak plasma concentration after unilateral TAP blocks, with no remarkable effects on block characteristics or duration.