How long does it take phentolamine to reverse adrenaline-induced vasoconstriction in the finger and hand? A prospective, randomized, blinded study: The Dalhousie project experimental phase.

At the Dalhousie Plastic Surgery Alumni Reunion at the Atlantic Plastic Surgery meeting in Halifax, Nova Scotia, in September 2001, 22 subjects, including 18 certified hand surgeons, were injected with 1.8 mL of 2% lidocaine with 1:100,000 adrenaline in three places in one finger of each hand. One hour later, the same sites of one hand were injected with phentolamine (1 mg in 1 mL), and the other hand was injected with saline. Subjects were blinded as to which hand received the phentolamine. It took an average of 85 min for the adrenaline-injected fingers to return to normal colour after phentolamine injection. It took an average of 320 min for the adrenaline-injected fingers to return to normal colour after saline injection (no phentolamine). We also observed that lidocaine with adrenaline provided an average of 549 min of anesthesia in nonphentolamine-injected fingers. Phentolamine consistently and reliably reversed adrenaline-induced vasoconstriction in the finger.