A Prospective, Randomized Controlled, Single-Blinded Study to Assess the Effect of a 33-Gauge Needle Versus a 34-Gauge Needle on Pain Experienced During Injection of Local Anesthetic on the Face.

Background: Most pain experienced by patients during Mohs micrographic surgery is associated with the initial injection. Previous studies have shown that a smaller gauge needle (33-gauge vs 30-gauge) is associated with less patient-reported pain.

Objectives: To evaluate patient-reported pain levels following injection with a 33-gauge versus a 34-gauge needle.  Methods: During this prospective, randomized, controlled, single-blinded study, 480 patients were randomized into a 33-gauge versus a 34-gauge needle group. Pain levels following needle insertion were recorded using the validated numerical rating scale (VNRS)-11 scale.  Results: Injection of local anesthetic with a 34-gauge needle is associated with significantly less pain compared to a 33-gauge needle across all subgroups (P=0.007, average pain level 0.49 [34-gauge group] vs 0.79 [33-gauge group] rated on a 0-10 pain scale). Females, first-time Mohs patients, patients under age 65, patients with basal cell carcinoma, and those with tumor locations on the nose experienced the most pain reduction with the use of a 34-gauge needle.  Limitations: This was a single-blinded study; thus, the injector was able to see which needle was being used. This knowledge could have subconsciously affected the angle, speed, or force used to insert the needle.

Conclusions: Injections with a 33-gauge and a 34-gauge needle are both tolerated well and associated with minimal pain. While the pain reduction associated with using a 34-gauge needle is statistically significant, the use of a 34-gauge needle may be most clinically relevant for certain patient subgroups. J Drugs Dermatol. 2023;22(11): doi:10.36849/JDD.7689.