Another Injection-free method to effect analgesia when injecting botulinum toxin for palmar hyperhidrosis: cryoanalgesia
- Author(s): Lim, Erle CH;
- Seet, Raymond CS
- et al.
Published Web Locationhttps://doi.org/10.5070/D38r54b2tm
Another Injection-free method to effect analgesia when injecting botulinum toxin for palmar hyperhidrosis: cryoanalgesiaYong Loo Lin School of Medicine, National University of Singapore. email@example.com
Erle CH Lim, Raymond CS Seet
Dermatology Online Journal 13 (2): 25
We refer to the letter by Benohanian, in which the author highlights the potential problems associated with using Bier's block to effect analgesia prior to botulinum toxin (BTX) injections for palmar hyperhidrosis , and advocates the use of an injection-free technique to administer lidocaine. In this technique, a low-pressure device is used to administer lidocaine intradermally without a needle, after which BTX is injected intradermally. Although the authors state that reconstitution of lidocaine with BTX does not affect the potency of the toxin , most manufacturers advise injectors against so doing.
Palmar hyperhidrosis, a socially embarrassing condition, can be ameliorated by intradermal injections of Botulinum toxin (BTX). These injections are often painful. Treating physicians have attempted to reduce the pain associated with such injections by administering them under regional anaesthesia  or peripheral nerve blockade . Unfortunately, local anaesthetics can cause neurotoxicity by activating the p38 mitogen-activated protein kinase (MAPK) system, which is involved in apoptotic cell death . Although relatively safe in vivo, most patients undergo regional or local anaesthesia on an ad hoc basis. Patients with palmar, axillary or plantar hyperhidrosis, however, receive BTX injections as often as every 3 months (though usually less often). The long-term effects of prolonged and repeated injections of local anaesthetic agents have not been assessed in patients, and it is possible that permanent neurotoxicity may result. These concerns have likewise been echoed by Benohanian .
Some injectors have reported efficacy with topical anaesthetic agents such as EMLA cream, but these often take between 30 to 45 minutes to work. Lately, several authors have reported the efficacy of iontophoretic administration of BTX [6, 7], though quantitative comparisons between iontophoretic administration and injections have yet to be performed.
We would like to highlight other techniques for achieving analgesia without the use of needles. The use of low temperatures to effect analgesia, ie., cryoanalgesia, allows injectors to inject BTX for palmar hyperhidrosis without use of local anesthetics. Kontochristopoulos et al.  compared two techniques of cryoanalgesia, using dichlorotetrafluoroethane spray and ice packs, and concluded that ice packs were less effective than dichlorotetrafluoroethane spray. Ice packs and iced water may, we feel, be equally effective in reducing the pain of the injections.
In our practice, we have eschewed regional anaesthesia and peripheral nerve blocks in view of the potential neurotoxocity of injected anaesthetic agents, and have instead applied EMLA cream, iced packs, ethyl chloride spray and lately, iced water. In this last method, the patient soaks his/her hand in a container of iced water for a few minutes prior to the procedure, repeating the procedure as necessary. Our patients have been equally happy with all techniques of cryoanalgesia. Indeed, one of us receives intradermal BTX for palmar hyperhidrosis , and has found the cryoanalgesia from iced water to be more effective than either ethyl chloride spray or ice packs. The energy consumed when ice melts (latent heat of melting) causes the surrounding air, water or solid surface (palm) in contact with it to cool. The efficacy of iced water over ice packs may be explained by 1) the increased surface area of the palm in contact with the iced water and 2) the fact that water is a better conductor of heat than air, which intervenes between solid ice and the hand when ice packs are used.
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