Sir: Plastic surgeons commonly administer subcutaneous epinephrine to reduce operative blood loss. In the pediatric population, delivering enough epinephrine-containing local anesthetic to adequately cause vasoconstriction around large vascular lesions can be difficult. The younger the child, the less volume of local anesthetic that can be used based on the patient's weight. We present an evidence-based evaluation of the maximum amount and optimal concentration of subcutaneously delivered epinephrine. Although epinephrine has the potential to cause tachycardia, hypertension, and arrhythmia, its subcutaneous administration in healthy patients is very safe. As much as 10 mg of epinephrine 1:1,000,000 may be given to an adult as part of tumescent solution (0.12 mg/kg). Serum epinephrine levels may be elevated four times normal but are equivalent to those associated with exercise and are well below toxic concentrations.1,2 Hemodynamic parameters are normal, and signs of catecholamine overdose have not been noted.1,2 Although systemic effects of more concentrated solutions of epinephrine are unknown, 200 ml of 1:200,000 epinephrine every 10 minutes in an adult (3 ml/kg every 10 minutes) was the recommended limit in the past for patients receiving halothane anesthesia, which lowered the arrhythmogenic threshold to epinephrine.3 To minimize the amount of epinephrine that is absorbed, the lowest dose required to achieve vasoconstriction should be used. Concentrations between 1:100,000 and 1:400,000 are equally effective and give superior vasoconstriction compared with more dilute solutions, although epinephrine 1:800,000 and 1:1,000,000 also cause vasoconstriction.4,5 As epinephrine becomes increasingly diluted, its onset and time to peak serum concentration are prolonged, and its duration of action is shortened. For example, epinephrine 1:1,000,000 has an onset of 15 minutes and a peak serum concentration of 3 hours, compared with 7 minutes and 30 minutes, respectively, with epinephrine 1:200,000.3,6 Although the vasoconstrictive effect of epinephrine 1:200,000 lasts for 60 to 90 minutes, its duration of action is shortened if diluted to 1:400,000 or greater.6 Although a maximum dose of subcutaneous epinephrine has not been defined, if tachycardia and hypertension develop, they may be managed by the anesthesiologist, if necessary. In patients with potential contraindications to epinephrine, the risk of its subcutaneous administration must be weighed against the benefits of adequate vasoconstriction: reduced blood loss, shorter operative time, prevention of iatrogenic injury, and less risk of hypotension and blood transfusion. For a pediatric patient who requires resection of a large vascular lesion, we favor diluting a lidocaine solution containing epinephrine (1:200,000) with an equal amount of saline to double the volume available for injection. The resulting epinephrine concentration (1:400,000) is as effective as the original concentration, although its duration of action may be shorter. The local anesthetic reduces pain and thus endogenous catecholamine production, which might potentiate a systemic response to the injected epinephrine. Lidocaine also may protect the myocardium because of its antiarrhythmic activity. Allen S. Liu, M.D. Department of Plastic and Oral Surgery Charles D. Nargozian, M.D. Department of Anesthesia Arin K. Greene, M.D. Department of Plastic and Oral Surgery Children's Hospital Boston Harvard Medical School Boston, Mass.