Pharmacokinetics of levobupivacaine following infant spinal anesthesia

Summary Background Infant spinal anesthesia with levobupivacaine has been promoted as a technique to reduce both the risk of postoperative apnea and exposure to volatile anesthesia. There is, however, no pharmacokinetic data to support the currently recommended doses. Aims Our aim was to determine whether infant levobupivacaine spinal anesthesia is associated with plasma concentrations consistent with a low risk of local anesthetic systemic toxicity. Methods This was an open‐label pharmacokinetic safety and tolerability study of levobupivacaine spinal anesthesia in infants <55 weeks Post Menstrual Age undergoing lower abdominal surgery. Infants received a spinal anesthetic with levobupivacaine 1 mg·kg −1 in the left lateral position. Results Spinal anesthesia was successful in 25 (86.2%) of 29 infants (postmenstrual age 36–52 weeks; weight 2.2–4.7 kg). The median ( IQR ) total venous levobupivacaine plasma concentrations was 0.33 (0.25–0.42) μg·ml −1 and unbound venous levobupivacaine was 19.5 (14.5–38) ng·ml −1 . Median protein binding was 93.5 (91.4–96%). Alpha‐1 acid glycoprotein concentrations were 0.25 (0.17–0.37) g·l −1 and albumin concentrations were 29 (24–32) g·l −1 . Conclusion Total plasma concentrations and unbound (free) concentration of levobupivacaine were consistently lower than concentrations reported in cases of pediatric local anesthetic toxicity. In a small number of infants requiring a repeat spinal of 1 mg·kg −1 was also associated with acceptable total and free concentrations. We conclude that levobupivacaine at 1 mg·kg −1 is associated with no systemic side effects in infants receiving awake spinal anesthesia.