Impact of Intravenous, Perioperative-Administrated Lidocaine on Postoperative Serum Levels of Endogenous Opioids in Children

Background: Endogenous opioids are neuropeptides involved in pain-relieving processes. In the periphery, they are synthesised and stored in cells of the immune system. Objective: In the current study, we describe the influence of perioperative, intravenous (i.v.) lidocaine infusion in children on postoperative, serum endogenous opioid concentrations in children. Methods: Forty-four children undergoing major spinal surgery were enrolled in the cohort study. They were divided into two groups: group A (n = 21) generally anesthetised with fentanyl, propofol, rocuronium, a mixture of oxygen/air/sevoflurane and with analgetics and co-analgetics: morphine, acetaminophen, metamizole, gabapentin, dexamethason and group B (n = 23) where, in addition to the above-described general anesthesia, patients were given i.v. lidocaine as a co-analgesic. We also recruited 20 healthy age- and gender-matched children (group C). We measured endogenous opioid levels in serum using immunoenzymatic methods. We evaluated postoperative pain intensity using a numerical or visual pain scale and demand for morphine. Results: The levels of measured endogenous opioids were similar in the control and in the studied groups before surgery. We noted that group B patients had lower pain intensity when compared to group A subjects. In group B, the elevated serum concentrations of β -endorphin, enkephalin and dynorphin in the postoperative period were reported. We also observed that the levels of endogenous opioids negatively correlated with morphine requirements and positively correlated with lidocaine concentration. Conclusion: Multidrug pain management including lidocaine seems to be more efficient than models without lidocaine. The endogenous opioid system should be considered as a novel target for pain relief therapy in children.