Maximum Dose of Plain Epinephrine in Plastic Surgery: Room to Explore

Epinephrine mixed with local anesthetics such as lidocaine or bupivacaine is routinely used in plastic surgery to increase the maximum safe dosage of local anesthesia and reduce blood loss through vasoconstriction. The pharmacokinetics of these epinephrine-local anesthetic combinations has been well studied, leading to well-established guidelines for maximum local anesthetic doses.1 However, local anesthetics have an associated toxicity risk and prevent impulse transmission/stimulation of motor nerves, which is particularly relevant in peripheral nerve surgery. As an alternative, plain epinephrine may be used to decrease blood loss and minimize blood within the surgical site. For this reason, it is commonly used in a wide range of plastic surgery procedures, including peripheral nerve surgery, body contouring procedures, cosmetic procedures performed under local anesthesia, and pediatric craniofacial surgery. In this Viewpoint, we examine the existing literature on the maximum dose of subcutaneous plain epinephrine and advocate for further research to guide the establishment of a maximum epinephrine dose. Within the literature, there have been reports of excessive epinephrine use causing systematic changes to patients’ physiology. These include increases in heart rate, cardiac index, and decreases in both mean arterial pressure and systemic vascular resistance index,2,3 which may be significant for patients with high-risk cardiovascular conditions. For this reason, plastic surgeons may act conservatively regarding maximum epinephrine dosing despite potential benefits with increased dosing. Additionally, studies of the vasoconstrictive effect of different epinephrine concentrations are almost exclusively conducted using epinephrine combined with local anesthetics.4 Kinsella et al have also identified this gap in the literature and studied the use of local epinephrine infiltration without local anesthetic in 102 palatoplasties, concluding that doses up to 10 μg/kg every 30 minutes did not lead to any cases of unstable tachycardia or hypertension.3 Similarly, Swan et al demonstrated no significant difference in heart rate, systolic blood pressure, or diastolic blood pressure in their high volume palatoplasty center when using 8 μm/kg of epinephrine mixed with 2 mg/kg of levobupivacaine.5 A recent review of the literature demonstrated that concentrations of epinephrine between 1:50,000 and 1:400,000 provide superior vasoconstrictive effects compared with dilute epinephrine concentrations.1 Given the frequency of use and potential benefit of plain epinephrine in a variety of surgical procedures, the lack of literature in this area warrants further investigation. The first step in addressing this gap is to establish a reference range by conducting a comprehensive review of clinical series in which epinephrine was used without hemodynamic complications. Next, small and large animal models should be used to establish preliminary dosing guidelines before human trials. Although basic science and clinical trials of this caliber would be logistically challenging and have significant associated costs, the authors believe that this gap in knowledge is worth highlighting for plastic surgeons, researchers, and trainees. DISCLOSURE The authors have no financial interest to declare in relation to the content of this article.