Table 3.

Practical guide for the use of NFII to treat palmar HH prior to BoNT-ONA injection with needles

Useful tips

1. Jet anesthesia prior to BoNT-ONA injection with needle is a practical pain management technique used by the authors to treat palmar or plantar HH.

2. The volume is set between 0.07 and 0.1 mL per spurt.

3. The initial driving pressure is set to 140 psi, but it could be increased by increments of 10 psi until a wheal or a tiny blood spot appears on the skin surface indicating the site where the needle should be inserted. The average pain score reported with this technique varies from 0 to 2 on a scale of 0 to 10.

Advantages

I. Tiny amount of lidocaine is used.

II. Immediate analgesia and reduced bleeding: needle injection into the dermis, as compared to the subcutaneous tissue, meets an elevated level of resistance that is felt on the syringe plunger,65 and therefore, injection should be performed slowly to minimize pain. This resistance may cause a reflux up to 15% of the total amount of BONT-ONA injected. Some experts have even suggested the suction of the B0NT-ONA droplets on the skin surface caused by backflow and their reinjection.38 The authors did not observe any B0NT-ONA reflux when jet anesthesia was used as the pain management method.

III. On the other hand, jet injection produces a superficial wheal formed by increased tissue pressure caused by the anesthetic fluid. The increased pressure compresses blood vessels, resulting in reduced bleeding, contrary to the nerve block technique, which induces reactive hyperemia that increases the tendency to bleed and causes waste of the expensive BoNT-ONA.

IV. Broader diffusion: the injected liquid has a bulb-shaped distribution with the broadside facing the muscle fascia and the narrow side underneath the epidermis.36 Jet injection distributes lidocaine more extensively into the dermis, thereby allowing BoNT-ONA to reach a greater number of eccrine glands than it would originally do if it would be limited along the needle injection track alone.

V. Avoidance of muscle weakness of the hands by allowing injection of BoNT-ONA as superficial as possible in the dermis where most “free nerve endings” for pain sensation are located. Without anesthesia, subcutaneous injections of BoNT-ONA were found to be relatively less painful than superficial dermal injections, but these deep injections, because of their proximity to the muscles, can cause handgrip weakening.66–68

VI. Vagal symptoms occur less frequently with this technique than the nerve block technique and, when they do, they are much milder.

VII. Patients can drive back home safely after the treatment session while patients who had a nerve block at the wrist can hardly do so.

Abbreviations: BoNT-ONA, onabotulinum toxin A; HH, hyperhidrosis; NFII, needle-free intradermal injection.