Local Anesthesia and Electronic Injector

At room temperature, 1% lidocaine combined with 1:100,000 epinephrine was used as a local anesthesia. The electronic constant-speed injector, i-JECT® (MediHub Inc., Gyeonggi-do, Korea) (Figure 1) was used, and the injection speed of the injector was set at level 1 (0.25 mL/s) or level 2 (0.4 mL/s). The injection site in a patient was divided into two sides (left and right). The method of local infiltration (manual or using the electronic injector) was randomly assigned to each side of the surgical field, and 2.5 cc (0.5 cc at five separate areas) of local anesthetic was injected individually using a 5 cc syringe with a 31-gauge needle. All injections were administered by a single surgeon (Sung Joo Tommy Hwang) to reduce inter-operator variation.