title: Optimal concentration of epinephrine for vasoconstriction in ear surgery.
abstract: OBJECTIVE
  To determine the optimal concentration of epinephrine required for vasoconstriction in ear surgery by evaluating changes in laser doppler blood flow.
  
  
  METHODS
  Prospective, randomized, double-blinded.
  
  
  METHODS
  Forty subjects undergoing surgical procedures under general anesthesia were injected in a standard posterior external auditory canal block with 1 mL of 1% lidocaine containing varying concentrations of epinephrine (nil, 1:50,000, 1:100,000, or 1:200,000) determined by randomization. Ear canal blood flow measurements were then made at 1-minute intervals for a 10-minute period using a laser doppler flow meter and compared with baseline blood flow.
  
  
  RESULTS
  The control solution of 1% lidocaine had a significantly higher blood flow than the epinephrine-containing solutions with an actual 200% increase in blood flow for the first 5 minutes before returning to baseline. All epinephrine-containing solutions had an approximately 50% decrease in blood flow from baseline over the 10-minute period as compared with the control which was statistically significant (P < .0001). There was no significant difference between the blood flow reduction of 1:50,000, 1:100,000, and 1:200,000 epinephrine-containing solutions (P = .8875).
  
  
  CONCLUSIONS
  One percent lidocaine control exhibited the expected initial vasodilatory effect for approximately 5 minutes. In this experimental model, using a lower concentration of 1:200,000 epinephrine would supply equivalent vasoconstriction in the ear compared with higher concentrations, thus reducing the possible systemic toxicity and related morbidity.
authors.affiliation: Department of Otolaryngology, Naval Medical Center, Portsmouth, Virginia 23708, USA.
authors.forename: E M
authors.initials: EM
authors.lastname: Gessler
authors.forename: A K
authors.initials: AK
authors.lastname: Hart
authors.forename: T M
authors.initials: TM
authors.lastname: Dunlevy
authors.forename: J H
authors.initials: JH
authors.lastname: Greinwald
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000768:Anesthesia, General; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004427:Ear Diseases / Q000601:surgery*; D004837:Epinephrine / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008012:Lidocaine; D008297:Male; D008875:Middle Aged; D009407:Nerve Block; D011446:Prospective Studies; D014661:Vasoconstriction / Q000187:drug effects*
chemical_list: D008012:Lidocaine; D004837:Epinephrine