The antinociceptive effect of esmolol

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http:// creativecommons.org/licenses/by-nc/3.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. CC Esmolol is the first intravenous, short-acting, titratable β-blocker available for use in critical care and surgical settings [1]. Esmolol is thought to be a " jack of all trades " among drugs used in anesthesia because it prevents and treats cardiovascular responses due to perioperative stimuli. In addition to its effect on the sympathetic nervous system, esmolol influences core components of an anesthetic regimen, such as analgesia, hypnosis, and memory function [2-5]. In this edition of the Korean Journal of Anesthesiology, Lee and Lee [6] studied 60 patients who underwent a laparoscopic appendectomy under total intravenous anesthesia using propofol and remifentanil and compared a control group with another group that received continuously injected esmolol during anesthesia. Postoperative 30 minute visual analog scale (VAS) scores and diclofenac sodium use for postoperative pain control during the first 24 hours decreased significantly in the esmolol group. Also, Lee and Lee [6] adjusted the infusion rate of remifentanil to target the bispectral index (BIS) to 40-60, compared to the control group, and the total amount of remifentanil administered during approximately 57 minutes of anesthesia was significantly lower in the esmolol group. The authors attributed the decrease in postoperative pain with esmolol to its intrinsic analgesic effect, a decrease in hepatic metabolism of opioids by β-blockers to extend the analgesic effect, and a reduction in opioid tolerance. However, there are several points that Lee and Lee [6] must consider. First, β-blockers, which decrease hepatic opioid metabolism and lengthen the analgesic effect, are limited only to those metabolized by the liver. For example, propranolol decreases its own metabolism and that of certain other drugs by eliciting a reduction in hepatic blood flow [7]. This could affect the metabolism of drugs with a large hepatic extraction ratio, such as fentanyl, and it would seem likely that propranolol use would result in prolonging the analgesic effect of fentanyl and also elicit a reduction in postoperative opioid consumption [2]. However, although the effect of esmolol on drug metabolism has not yet been thoroughly investigated, unlike most β-blockers, which are metabolized by the liver, esmolol is metabolized by esterases located in the cytosol of red blood cells [8]. Thus, it seems unlikely that …