Non-Opioid Anesthesia with Esmolol Avoids Opioid-Induced Hyperalgesia and Reduces Fentanyl Requirement After Laparoscopy

Abstract

To the Editor: Collard et al.1 demonstrated that substituting an esmolol infusion for intraoperative fentanyl or remifentanil reduced postoperative fentanyl demand, diminished nausea, and accelerated discharge after laparoscopic cholecystectomy. The study design with two interventions in the same group (eliminating opioids and adding esmolol infusion) does not establish the definite cause-effect relationship. Opioids provide an initial analgesic effect, but then reduce the pain threshold to less than baseline (opioid-induced hyperalgesia [OIH]) and increase the amount of drug required to achieve the same analgesia (tolerance).2,3 Remifentanil has been shown to increase pain and induce mechanical hyperalgesia after 30 min infusion at the dose 0.05–0.1 μg · kg−1· min−1 in volunteers.4–6 An alternative explanation for the decreased postoperative fentanyl requirement originally attributed to esmolol infusion1 is that non-opioid anesthetic technique does not cause OIH and tolerance. Both β-blockers and opioids blunt the sympathetic response to nociception during the surgery, whereas a subanesthetic dose of inhalational anesthetics exacerbates this response.7 However, deepening inhaled anesthesia can achieve similar hemodynamic stability in most patients with additional benefit of anesthetic-induced preconditioning.8 OIH is modulated by anesthesia technique (e.g., use of N-methyl- d-aspartate antagonists), and some clinical studies have failed to demonstrate increased pain scores after remifentanil infusion.9 Whether postoperative opioid sparing is caused by the intraoperative opioid avoidance or an intrinsic β-blocker opioid sparing effect remains to be answered in additional studies. Study groups should be matched for intraoperative opioid usage (receive either none or the same dose). Collard’s group finding that esmolol in the absence of opioids decreases the postoperative fentanyl requirement is clinically significant and relevant for ambulatory surgery. The question as to whether the diminished postoperative analgesic requirement after minimally invasive surgery is a result of presence of esmolol, absence of opioids or combination of these interventions remains to be answered. Mindaugas Pranevicius, MD Department of Anesthesiology Albert Einstein College of Medicine Jacobi Medical Center Bronx, New York [email protected] Osvaldas Pranevicius, MD, PhD Department of Anesthesiology New York Hospital Queens Flushing, New York Dr. Carli does not wish to respond.