Three separate nerves to block in the finger.
The addition of sodium bicarbonate to local anesthetics shortens the onset of action by raising tissue pH, reducing the pain of injection.4,5 Lidocaine can be buffered by adding 1 mL of sodium bicarbonate 8.4% (1 mEq/mL) to 9 mL of 1% lidocaine. Bupivacaine can be buffered by adding 1 mL of sodium bicarbonate 8.4% (1 mEq/mL) to 29 mL of bupivacaine 0.25%. However, the mixture of bicarbonate can cause precipitation of the anesthetic agent (most prominently bupivacaine) and accelerate the degradation of epinephrine in the solution, so bicarbonate should not be added to the anesthetic unless it can be used immediately. Aspiration before injection helps to avoid inadvertent deposit of local anesthetic in a vein or artery. The addition of epinephrine to the injected local anesthetic solution increases the duration of anesthesia, helps to control wound bleeding, and slows the systemic absorption.7 The use of local anesthetic with epinephrine appears to be safe for use in end-arterial fields (fingers, toes, etc.) in selected healthy patients,8-10 but probably should be avoided in suspected digital vascular injury; patients with vascular disease, such as Raynaud or Berger disease; or other conditions in which end-arterial vascular supply is problematic. In patients with true allergies to local anesthetics diphenhydramine 50 mg/mL can be used. Consider topical anesthetics whenever appropriate.