Adrenaline and Anesthesia - Clinical Review

Abstract Adrenaline or epinephrine is one of the primarily important catecholamines in the general stress response and is manufactured in the adrenal medulla. In stress, it is secreted into the blood circulation and evokes many bodily transformations which prepare the body for the fight or flight response, some of which include tachycardia and hypertension, dilation of the air passages, and mobilization of energy reserves. This catecholamine surge can, however, cause myocardial stress, as evidenced during acute ischemia, hence an implication of increased risk of myocardial injury. In terms of functioning at the molecular level, adrenaline interacts with adrenergic receptors, which trigger intracellular processes associated with the readiness of a body to act fast as well as affecting more general forms of cardiac activity. Adrenaline stimulates beta-adrenergic receptors, enhancing heart rate and contractility, vital under stress but harmful with constant exposure. It is metabolized in the liver and may also cause dysrhythmias when used together with some inhaled anesthesia such as halothane. In anesthesia, adrenaline gets used to increase the local anesthetic action of the drug by constricting blood vessels and thereby increasing the duration and extent of analgesia besides reducing the uptake of the anesthetic into the systemic circulation. The common dose schedule is 1 in 2 lakh of adrenaline which means 5 μ/mL. The usual dose should not increase to 3 μ/kg. Preferably, the dose can be supplemented after 10–15 min. The use of adrenaline also creates a plane to dissect. The duration of action of local anesthetic drug is prolonged following the addition of adrenaline. Epidural test doses detect accidental intravascular catheterization. There is evidence that adrenaline belongs to anesthetic protocols, enabling deeper anesthesia, which, in turn, contributes to more effective outcomes of the surgery and easier recovery. Adrenaline by way of its alpha 2 agonism is likely to increase the effects of local anesthetic drugs and inhalational agents. Still, practitioners must address those benefits against possible side effects since minor, albeit significant, changes in the electrocardiographic characteristics have been recorded with lignocaine–adrenaline mixtures. Adrenaline nebulization is used for acute respiratory conditions like croup postextubation. The dose is 0.5 mg/kg, max 5 mg, diluted in 2–3 mL saline, repeated every 30 min if needed, with monitoring for tachycardia and hypertension. For perioperative anaphylaxis, administer 0.5 mg intramuscular for adults, adjusted by age for children. Hence, adrenaline is extremely useful in local anesthesia because of its vasoconstrictive effects, which must, however, be monitored continuously for patient and operational safety.