Analgesic Effect of Intraoperative Esmolol in Mastectomies: Single Center, Prospective, Double-blind, Randomized and Placebo Controlled Study

Controlled hypotension is an anesthetic-surgical approach that matches the reversible and deliberate reduction in blood pressure during surgery period which aims to achieve values below 50% of normal values or mean arterial pressure (MAP) from 50 to 65 mmHg.

This technique is especially beneficial in patients undergoing procedures requiring control of bleeding for proper surgical field. The method provides a better view of anatomical structures, reduced surgical time and a significant decrease in the need for blood transfusions, with the added benefit of preventing possible complications from it.

Several drugs have been used in this scenario, as halogenated, opioids, alpha-2-agonists and beta-blockers, among which the esmolol emerges as effective and promising drug.

Esmolol is a selective beta-blocker whose action inhibits preferably the beta type 1 receptors with decreased heart rate (HR) and cardiac inotropic and consequent decrease in consumption of myocardial oxygen. Its half-life of distribution is approximately 2 minutes, the elimination half-life of 9 minutes with 55% protein bound. The duration is short due to rapid metabolism by hydrolysis by esterases in plasma and results in an inactive metabolite with negligible amounts of methanol. It has low solubility, which limits their passage through the blood-brain and placental barrier. Thanks to these features, the esmolol constitutes the most appropriate beta-blocker for intravenous use under continuous infusion.

The use of a selective beta-blocking agent continuously infused intraoperative period as well as promoting adequate blood pressure control in the controlled hypotension, it has additional advantages over other anesthetic agents, such as cardioprotection obtained by suppressing the cardiovascular response to catecholamines released during stress surgical and sympathetic stimulation resulting from laryngoscopy and tracheal intubation. The suppression of cardiovascular adrenergic response allows better coronary perfusion with proven benefits in reducing the incidence of perioperative myocardial ischemia and influence on mortality and morbidity of patients, especially coronary and high risk for ischemic phenomena. There are also several studies that demonstrate the importance of esmolol in the control and prevention of sympathetic response during extubation, better hemodynamics during induction, maintenance and emergence from anesthesia, fewer complications, lower incidence of perioperative nausea, time decreased from room to stay anesthetic recovery and, due to reduced cardiac work, action prolongation of neuromuscular blockers and opioids, saving their use. There are still ongoing studies with important indications that there is potentiation of analgesia and the hypnotic component of anesthesia with the use of esmolol.