A Practical Guide to Local Anesthetic Options for Wide-awake Hand Surgery (WALANT): A Laboratory-based Experimental Study.

Ongoing supply chain issues are impacting local anesthetic availability, limiting choices for hand surgery under local anesthesia (wide-awake local anesthesia no tourniquet [WALANT] hand surgery). WALANT can be safely performed using multiple local anesthesia preparations; however, epinephrine (for hemostasis) and sodium bicarbonate (NaHCO) (to reduce injection pain) are often added to create the desired preparation. Here, we tested how much NaHCO to add to various local anesthetic to approximate body pH. Five samples of each commercially available local anesthetics were tested for pH including 1% lidocaine, 2% lidocaine, 1% lidocaine with 1/200,000 epinephrine, 0.25% bupivacaine, 0.5% bupivacaine, 0.5% bupivacaine with 1/100,000 epinephrine, 1% mepivacaine, 2% mepivacaine, and ropivacaine, with or without premixed or exogenous epinephrine. Each sample was buffered with NaHCO, with volumes increasing by 0.1 mL until target pH was measured or visible precipitate occurred; 1.0 mL of 8.4% bicarbonate can be added to 10 mL of 1% lidocaine with 1/100,000 exogenous epinephrine to yield pH 7.3. Similarly, with 10 mL 1% lidocaine with premixed 1/200,000 epinephrine, the ideal volume of buffer remains 1.0 mL. Buffering bupivacaine created a solid precipitate in all samples when more than 0.2 mL of NaHCO per 10 mL of sample was added. Ropivacaine precipitated with all volumes of buffer. Mepivacaine can be buffered using 0.3 mL NaHCO per 10 mL to achieve physiological pH, without precipitate. In conclusion, we present guidance for surgeons to mix local anesthetic, epinephrine, and NaHCO to optimize pH for comfortable injection of local anesthesia in WALANT procedures.