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Vasoconstriction time of epinephrine in scalp correlates to concentration

Vasoconstriction time of epinephrine correlated with concentration and location of injection on the scalp, according to recently published study results.

“Effective perioperative control of bleeding is critical during hair transplantation due to its time-consuming nature,” Young-Cheon Na, MD, PhD, of the department of plastic and reconstructive surgery, Wonkwang University Hospital, Iksan, South Korea, and colleagues wrote.

The researchers enrolled 25 volunteers (12 males; mean age, 28 years) with no history of forehead augmentation or hair transplantation, who were injected with epinephrine at two sites: On the path of the supraorbital artery on the anterior hairline in the midfrontal area (point A), and the frontotemporal junction of the frontal hairline (point B). Concentrations of injected epinephrine were 1:400,000, 1:200,000, 1:100,000 and 1:50,000, with only one injection performed per day to prevent interference between injections, for a total of eight clinic visits.

Scalp blood flow and vasoconstriction time at points A and B with each concentration of epinephrine was recorded using laser Doppler.

There were no adverse events reported.

Mean vasoconstriction times at point A were 13.6 minutes for 1:400,000 epinephrine; 15.9 minutes for 1:200,000, 34 minutes for 1:100,000 and 40.3 minutes for 1:50,000 concentrations, while at point B, the times were 15.7 minutes, 20.8 minutes, 39.8 minutes and 52.7 minutes, respectively.

There was no difference in the time points, except for when 1:50,000 epinephrine was used (P < .05).

“Epinephrine is used with local anesthetics in almost all surgical procedures where infiltration anesthesia is required; mixtures with 1:100,000 and 1:200,000 epinephrine are used most commonly,” the researchers wrote. “Our findings suggest that surgeons should consider the differences in epinephrine’s action in different regions or areas of vessel distribution before clinical application.”

 “The vasoconstriction time of epinephrine in the scalp was correlated to concentration and was greatest at the concentration of 1:50,000,” the researchers concluded. “The duration of action was longer at the frontotemporal recess of the frontal hairline compared with the area of the supraorbital artery at the hairline. This suggests that vasoconstriction time differs according to the site of the injection in the scalp. Our findings will be of interest to surgeons operating on the scalp and help guide their choice of epinephrine concentration and site of injection.” – by Bruce Thiel

Disclosure: The researchers report no relevant financial disclosures.