Epinephrine Vasoconstriction Effect Time in the Scalp Differs According to Injection Site and Concentration.

[BACKGROUND] There have been few studies of the action of epinephrine injected into scalp tissue, or whether the action of epinephrine differs according to vascular anatomy within the same surgical field. Effective perioperative control of bleeding is critical during hair transplantation due to its time-consuming nature.

[OBJECTIVE] To identify the vasoconstriction time of epinephrine by concentration and injection site in the scalp tissue.

[METHODS] Twenty-five volunteers were injected with epinephrine at concentrations of 1:400,000, 1:200,000, 1:100,000, and 1:50,000 in the path of the supraorbital artery on the anterior hairline in the midfrontal area (Point A) and at the frontotemporal junction of the frontal hairline (Point B). Laser Doppler was used to measure scalp blood flow, and vasoconstriction time at Points A and B with each concentration of epinephrine was recorded.

[RESULTS] The duration of action of epinephrine increased in direct proportion with the concentration of epinephrine. The duration of vasoconstriction was shorter at Point A than at Point B, but this difference was only statistically significant at an epinephrine concentration of 1:50,000.

[CONCLUSION] The vasoconstriction time of epinephrine in the scalp correlated positively with concentration, and the duration of vasoconstriction was longer at Point B than at Point A.