Esmolol
Another group of drugs that are used in off-pump CABG, belongs to β-adrenergic antagonists (β blockers) among them, Esmolol (ESM), by reducing the extent of myocardial injury during ischemia and coronary reperfusion. It is believed that the negative inotropic and chronotropic effects of these drugs concomitantly reduce myocardial oxygen consumption (MVO2) and decrease sympathetic tone, thereby exerting a beneficial effect on the ischemic myocardium. However, most β blockers are known for prolonged negative inotropic properties, which limits their use during cardiac surgery (2 )(3 ).
Esmolol (ESM) belongs to the Β blocker drug group (ultra-short-acting β1 selective-adrenergic blocker). It presents a rapid action onset of 1-2 minutes in which it is quickly metabolized by red blood cell esterase; its elimination half-life (T ½) is 9 -10 min. The rapid onset of action of this agent and its short duration of effect is an advantage in the perioperative period. The drug can be administered either as a bolus injection or as a continuous intravenous infusion. It is commonly administered in doses of 0,5mg/Kg and its effect stops within 10-20 minutes of discontinuing the infusion (7 ).
In clinical studies (following hemodynamic resuscitation) ESM administration has shown a reductive effect of myocardial damage in the context of acute ischemia. A hemodynamic benefit has also been accepted by decreasing contractility, economizing cardiac work and decreasing cardiac energetic costs with a consequent reduction in oxygen consumption (MVO2) (8 ).At the cellular level, these drugs reduce mitochondrial respiration and phosphorylase activity, thus buffering the production of free radicals. Because hemodynamic changes are common in laryngoscopy, lidocaine is often administered intravenously 90 seconds before intubation in order to suppress laryngeal reflexes, and ESM may be used to reduce heart rate and blood pressure in response to post-laryngoscopy. ESM is an excellent option for attenuation of cardiovascular responses to airway instrumentation (9 ).