Liquid Nitrogen Spray Cooling for Reducing Injection Pain: A Pilot Study

Intralesional injection (ILI) represents one of the most common treatment modalities in dermatology due to its ability to deliver drugs directly into skin lesions with minimal sys-temic effects. Common indications for ILI include keloid, nail dystrophies, prurigo nodularis, alopecia areata and vitiligo 1 . Triamcinolone is the most frequently injected drug, with bleomycin and 5-fluorouracil also administered for different purposes. However, a major inconvenience is the acute pain caused by injection. Liquid nitrogen (LN2) spray is also frequently used in dermatologic clinics. Thus, we conducted a preliminary study to determine the degree to which LN2 spray cooling reduced the injection pain associated with ILI. A prospective, open trial was done with patients who vis-ited our clinic between July and August, 2018. Patients who had two or more lesions requiring ILI of 0.4 mg/cc triamcinolone acetate mixed with lidocaine on their hands or feet were recruited. Two lesions positioned similarly on the left and right were selected and randomized to ILI with or without the LN2 spray cooling. For the LN2 spray cooling, LN2 was sprayed shortly before injection at a distance of 20 cm for 3~4 seconds until the skin surface turned a transient white color and appeared frost-like (Fig. 1). We received the patient’s consent form about publishing all photographic materials. Then, a questionnaire was given to each patient to identify their acute pain level using a numeric rating scale (NRS, 0 to 10). All participants provided written informed consent and this study was approved by our institutional review board (VC-18ZESI0117). A total of 21 patients were in this study The