Translated from: Atención Primaria F. Caballero Martínez et al. Dermatological cryosurgery in primary care with Vol. 18 No. 5 (211, 216), September 30, 1996 dimethyl ether propane spray in comparison with liquid nitrogen DERMATOLOGICAL CRYOSURGERY IN PRIMARY CARE WITH DIMETHYL ETHER PROPANE SPRAY IN COMPARISON WITH LIQUID NITROGEN F. Caballero Martínez*, C. Plaza Nohales**, C. Pérez Canal**, M.J. Lucena Martín***, M. Holgado Catalán****, and G. Olivera Cañadas**** Unidad Docente de Medicina Familiar y Comunitaria. Unidad de Investigacion de Atención Primaria. Insalud Área 6 de Madrid, España. product transported in this way, it is CUTANEOUS CRYOSURGERY IN FAMILY MEDICINE: essential to use it within a few hours of DIMETHYL ETHER PROPANE SPRAY VERSUS LIQUID NITROGEN receipt of the same. In order to make Objective. To compare the efficacy, tolerance and safety of two types of cryotherapy, the method cost-effective, therefore, it performed by family physicians, for benign cutaneous lesions: low freezing (-57°C) with is necessary to gather together patients dimethyl ether propane cryogenic spray (DMEP) and intense freezing (-196°C) with to be treated on the days on which one conventional liquid nitrogen (LN). will be receiving the product. Design. A randomized, multi-centered, controlled clinical trial, with single-blind assessment. Setting. Three primary care teaching teams in the Community of Madrid. Patients and other participants. Ten MIR from family & community medicine intervened. Since the treatment is excessively There were 124 patients, who had 174 benign cutaneous lesions, suitable for cryotherapy. dependent on the willingness of There were 3 voluntary withdrawals, none because of an adverse reaction. participants, this experience is still an Interventions. In each case there was local application for a standard time of the exceptional situation in Primary Care randomized agent. Control-group intervention, 81 cases: swab soaked in LN. Study-group in this field of medicine. In fact, in intervention, 93 cases: swab saturated with DMEP spray. Maximum of three freezings per June 1994, only 0.8% of tutors and case, at weekly intervals. third year resident general practitioners Measurements and main results. A doctor made a blind assessment of the results of the 26 Primary Care Teams of the (elimination, adverse reaction, aesthetic result) 15 days after treatment. Conclusions. No clinically relevant differences between the efficacy, tolerance and safety of Community of Madrid were regularly the two cryogenic agents used in primary care were found. The low freezing of DMEP was practicing cryosurgery, the usual sufficient for the cryotherapy of benign lesions. practice being to use less decisive alternatives (keratolytics) or, 1. INTRODUCTION molluscum contagiosum, seborrheic unnecessarily, to refer patients to busy and actinic keratoses...). Unfortunately, departments specializing in minor Dermatological cryosurgery enables because of its extremely low boiling pathology. destruction of a wide variety of point, the substance has to be stored in superficial skin lesions by controlled special containers which are not A coolant mixture of dimethyl ether freezing. Because of its safety and high available in the Health Centers in our and propane (DMEP) has recently level of effectiveness (1-4) and because environment. An infrastructural been marketed in aerosol form, which it is easy to learn to use the method, it deficiency is therefore the main is easy to administer and also to store; is widely used in Anglo-Saxon limiting factor for cryosurgery in its small container makes it easy to countries by doctors who are not general medical practice in Spain. transport and keeps it stable for three dermatological specialists (5-7). years with no special precautions. In our Teaching Unit, a regular supply Through evaporation this product The simplest method of freezing is of small quantities of the cryogenic reaches -57°C in its applicator swab. topical application on lesions which agent in portable, domestic type Our theory was that if this temperature, one wishes to destroy of a cottonwool thermos flasks from the reference which is markedly higher than that swab saturated by immersion in liquid Dermatological Department (Puerta de obtained with liquid nitrogen, was nitrogen (LN). This cryogenic agent, Hierro Hospital) has enabled us to found to be adequate for destruction of having a temperature of -196°C, is very carry out cryosurgery with liquid skin lesions, this kit would represent effective in elimination of a large nitrogen for the past few years, as a an answer to logistic problems standing variety of very common benign and routine method and with good results. in the way of practicing cryosurgery in premalignant skin lesions (verrucas, Because of the rapid evaporation of the the consulting rooms of general practitioners. The bibliography available to date on * General Practitioner, Coördinator of the Family and Community Medicine Teaching Unit of Madrid Area 6, Research leader INSALUD Research Center Area 6 Madrid, Spain. DMEP spray (11) describes some small ** Resident General Practitioner, Family and Community Medicine Teaching Unit, EAP Majadahonda, Madrid. *** Resident General Practitioner, Family and Community Medicine Teaching Unit, EAP Argüelles, Madrid. trials using the product without **** Resident General Practitioner, Family and Community Medicine Teaching Unit, EAP Pozuelo I, Madrid. control groups; the real effectiveness of Correspondence: F. Caballero Martínez. this low freezing cryosurgery is C/Urbano, 56 1 C therefore as yet unknown. In this 28010 Madrid, Spain study, we present the results of the The article is accepted for publication on May 29, 1996. Translated from: Atención Primaria F. Caballero Martínez et al. Dermatological cryosurgery in primary care with Vol. 18 No. 5 (211, 216), September 30, 1996 dimethyl ether propane spray in comparison with liquid nitrogen first clinical trial of the product in contrast having a level of significance correlative to the cases as included in comparison with standard cryotherapy of 0.05 and a study power of 0.80). the trial. It was permitted for one and with liquid nitrogen in elimination of Absence of the exclusion criteria stated the same patient to contribute up to a benign skin lesions, for the purpose of in Table 1 was confirmed in each case, maximum of three different lesions to providing the doctor with scientific and each patient’s specific consent was the trial, treated simultaneously or one criteria on the basis of which to assess requested after they had received oral after the other. In this situation each the advantage of the new therapeutic and written information. lesion was considered as one case, alternative in his daily practice. receiving its randomized treatment Procedures Compared. Freezing was according to a correlative cranio- 2. MATERIAL AND METHOD carried out by contacting the skin caudal order of anatomical location. lesions with identical cottonwool swabs (the swabs supplied in the Trial Variables and Assessment Criteria. Design of the Study. A controlled, DMEP kit) saturated in the cryogenic Clinical assessment of the patient was randomized, parallel experimental products by immersion for a minimum carried out at the time of inclusion in trial, with blind assessment of the of 10 seconds in LN (reference the trial, with recording of the main result, to compare the procedures) or by spraying with the characteristics of the skin lesion effectiveness of DMEP in elimination DMEP spray in accordance with the (diagnosis, size, location, number) and of benign skin lesions with standard manufacturer’s specifications (index the characteristics of the carrier patient cryotherapy (LN). Tolerance and safety procedures). Freezing times (swab-skin (sex, age, concurrent cutaneous of both systems are analyzed secondarily. contact) were standardized in pathology, previous treatments) which The trial was designed and monitored accordance with standard might influence the treatment result. in the Family and Community recommendations in the bibliography Follow-up of the cases was carried out, Medicine Teaching Unit of Madrid for each type of lesion: 20 seconds for as a minimum, one week after each Area 6, with the mandatory approval verruca plana and molluscum freezing and during an extra end-of-trial of the Clinical Research Ethics contagiosum, 40 seconds for verruca appointment 15 days after the last Committee of Puerta de Hierro vulgaris, verruca filiformis and application. Hospital. seborrheic keratoses, ensuring in each case that a perilesional halo of healthy A cure was considered obtained if a Scope and Period of the Trial. The field skin measuring from 1 to 3 mm was lesion was eliminated after freezing, work was carried out in the clinics of covered. In the event of incomplete i.e., if no vital skin findings compatible three Primary Care Teams of the elimination of the lesion, repetition with the original skin lesion were Teaching Unit (Majadahonda PCT was permitted up to a maximum of detected, even though after-effects of [=Primary Care Team], Arguelles PCT three freezings (or until such time as the therapy applied still persisted and Pozuelo de Alarcón PCT) by 10 the cure enabled assessment of the (necrotic residues of ampullae, epidermal third year house physicians assigned need for retreatment). denudation, depigmentation or other to the said centers during 1995, changes of coloration, cicatricial tissue). supervised by their respective tutors,