Onset and Duration of Anesthesia of Varying Lidocaine and Epinephrine Concentrations Used in WALANT

Background. Wide awake local anesthesia no tourniquet (WALANT) is an increasingly popular anesthetic technique used in hand surgery which uses local anesthetic and epinephrine, achieves adequate anesthesia, and eliminates the need for a tourniquet. Objective. This study compares the onset and duration of the three most commonly used concentrations of lidocaine and epinephrine for WALANT. Methodology. This was a randomized double-blind comparative study of 78 middle fingers subjected to either 1% lidocaine with 1:100,000 epinephrine, 0.5% lidocaine with 1:200,000 epinephrine or 0.25% lidocaine with 1:400,000 epinephrine. The pinprick test was used to measure onset time and anesthetic duration for the local effect and as a digital nerve block. Results. The contents of each treatment arm were as follows: Arm A: 0.25% lidocaine with 1:400,000 epinephrine, Arm B: 1% lidocaine with 1:100,000 epinephrine, and Arm C: 0.5% lidocaine with 1:200,000 epinephrine. Arm B had the shortest onset time (30.77 ± 10.39 seconds for local, 2.78 ± 0.69 minutes for digital block) followed by Arm C (38 ± 17.17 seconds for local, 4.30 ± 1.62 minutes for digital block) and Arm A (55.38 ± 18.48 seconds for local, 5.18 ± 1.46 minutes for digital block, p <0.001). A longer duration of anesthesia was achieved in both local and digital blocks for Arm B (5.07 ± 0.34 hours for local, 4.26 ± 0.33 hours for digital block) followed by Arm C (4.44 ± 0.31 hours for local, 3.36 ± 0.24 hours for digital block) then Arm A (3.01 ± 0.33 hours for local, 2.29 ± 0.29 hours for digital block, p <0.001). Conclusion. Higher concentrations of lidocaine and epinephrine provided faster onset and longer duration of anesthesia for both local block and digital nerve block. Lower concentrations in higher volumes may be sufficient for short procedures (less than three hours).