HAND/PERIPHERAL NERVE Optimal Time Delay between Epinephrine Injection and Incision to Minimize Bleeding Daniel E. McKee, M.D. Donald H. Lalonde, M.D. Achilleas Thoma, M.D., M.Sc. Diana L. Glennie, M.Sc. Joseph E. Hayward, Ph.D. Hamilton, Ontario, and Saint John, New Brunswick, Canada Background: The time until maximal cutaneous vasoconstriction after injection of lidocaine with epinephrine is often given in textbooks and multiple choice examinations as 7 to 10 minutes. However, in our experience, there is signifi- cantly less cutaneous bleeding if one waits considerably longer than 7 to 10 minutes after injection of local anesthesia with epinephrine for most procedures on human skin. Methods: This was a prospective, randomized, triple-blind study where 12 vol- unteers were injected simultaneously in each arm with either 1% lidocaine with epinephrine (study group) or 1% plain lidocaine (control group), after which the relative hemoglobin concentration of the underlying skin and soft tissues was measured over time using spectroscopy. Results: In the epinephrine group, the mean time at which the lowest cutaneous hemoglobin level was obtained was 25.9 minutes (95 percent CI, 25.9  5.1 minutes). This was significantly longer than the historical literature values of 7 to 10 minutes for maximum vasoconstriction after injection. Mean hemoglobin index values at every time measurement after postinjection minute 1 were significantly different between the study group and the control group, with use of a two-tailed paired t test (p  0.01). Conclusions: If optimal visualization is desired, the ideal time for the surgeon to begin the incision should be 25 minutes after injection of local anesthetic with epinephrine. It takes considerably longer than 7 to 10 minutes for a new local equilibrium to be obtained in relation to hemoglobin quantity. (Plast. Reconstr. Surg. 131: 811, 2013.) CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, I. E pinephrine is routinely used with local an- esthetic in surgical procedures to provide hemostasis, where visualization of under- lying intricate anatomy is important. The time until maximal cutaneous vasoconstriction after injection of lidocaine with epinephrine is often listed in textbooks 1,2 and multiple-choice examinations as 7 to 10 minutes. This value originated from a 1987 study using a laser Doppler flowmeter on pig skin after injection of 1% lidocaine with epinephrine at several concentrations, including 1:100,000. 3 In our clinical experience, there is significantly less cu- taneous bleeding if one waits considerably longer than 7 to 10 minutes after injection of local an- esthesia with epinephrine for most procedures on human skin. The purpose of this study was to see how long it really takes to obtain the lowest cutaneous hemoglobin concentration after lidocaine with epinephrine injection in the human arm. In this prospective, randomized, triple-blind study, vol- unteers were injected simultaneously in each arm with either 1% lidocaine (plain) or 1% lidocaine with epinephrine. The underlying skin and soft- tissue perfusion changes were monitored with dif- fuse reflectance spectroscopy to estimate relative hemoglobin concentration changes over time. The time until the lowest concentration of hemo- globin was obtained for each volunteer injected with lidocaine with epinephrine. From the Division of Plastic and Reconstructive Surgery, Department of Surgery, and the Department of Medical Phys- ics and Applied Radiation Sciences, McMaster University, and Saint John Regional Hospital, Dalhousie University. Received for publication August 4, 2012; accepted October 1, 2012. Copyright ©2013 by the American Society of Plastic Surgeons DOI: 10.1097/PRS.0b013e3182818ced Disclosure: The authors have no financial interest to declare in relation to the content of this article. No external funding was received. www.PRSJournal.com 811