The importance of bicarbonate in large volume anesthetic preparations. Revisiting the tumescent formula.
BACKGROUND
The tumescent local anesthetic approach is now being used more widely in dermatologic surgery. Although the original formula contains 12.5 mEq sodium bicarbonate per 50 mL of lidocaine, traditionally buffered solutions contain 1 mEq per 10 mL.


OBJECTIVE
This study examines the effects of changing the concentrations of sodium bicarbonate in the tumescent formula.


METHODS
Various concentrations of sodium bicarbonate in tumescent anesthetic preparations were measured for pH.


RESULTS
Tumescent anesthetic preparations containing 5 mEq/L have a more physiologic pH (7.41) than the classic formula of 12.5 mEq/L (7.73). Clinical use of this reduced sodium bicarbonate solution showed no difference from the original formula.


CONCLUSIONS
Sodium bicarbonate can be used in a 1 mEq per 10 mL of lidocaine ratio similar to other buffered anesthetic solutions. This solution is physiologic in pH. However, some thought should also be given to the pKa of lidocaine, which is at pH 7.9. To achieve this even higher concentration (20 mEq/L) bicarbonate must be added to the tumescent solution. Thought must be given to these concepts when tumescent solutions are used in large volumes.
Smith
S L
SL
Department of Dermatology, Tulane University School of Medicine, New Orleans, Louisiana.
Hodge
J A
JA
Lawrence
N
N
Badame
A J
AJ
Coleman
W P
WP
D000772:Anesthesia, Local; D000777:Anesthetics; D002254:Carbonates; D062109:Dermatologic Surgical Procedures; D004339:Drug Compounding; D006863:Hydrogen-Ion Concentration; D008012:Lidocaine
D000777:Anesthetics; D002254:Carbonates; C005686:sodium carbonate; D008012:Lidocaine