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Print version ISSN 0034-7094
On-line version ISSN 1806-907X
Rev. Bras. Anestesiol. vol.56 no.2 Campinas Mar/Apr. 2006
Prevalence of signs/symptoms suggestive of latex sensitization in health care workers*
Prevalencia de señales/síntomas sugestivos de sensibilidad al l átex en profesionales de la salud
Lígia Andrade da Silva Telles Mathias, TSA, M.D.I; Marcos P F Botelho, M.D. II; Laudinely M de Oliveira, M.D.III; Silvio J B Yamamura, M.D.III; Renato L G Bonfá, M.D.IV; Solange MarsuraV
do Serviço e Disciplina de Anestesiologia, ISCMSP e Faculdade de Ciências
Médicas da ISCMSP de São Paulo; Responsável pelo CET/SBA
IIMédico Residente de Radiologia da ISCMSP
IIIME do CET/SBA da ISCMSP
IVMédico Residente de Cirurgia da ISCMSP
VEnfermeira Gestora do Centro Cirúrgico da ISCMSP
AND OBJECTIVES: In the literature, the references on adverse reactions to
latex products have been significantly increasing for the last few years. However,
it lacks Brazilian data regarding the preva-lence of latex-related sensitization
in health care workers. The objective of this study was to evaluate the prevalence
of signs and symptoms suggestive of latex-related sensitization in health care
METHODS: Upon approval by the Ethics Committee it were selected a population of subjects from the Institution's departmental workforce: the Surgical Center Cleaning, Accounting and Nursing personnel and the physicians working at the Surgery, Gynecology, Obstetrics, Anesthesiology, Intensive Care Unit and Medical Clinics. After the informed consent has been obtained, the subjects were submitted to a questionnaire on: age, gender, professional category; type and length of time in contact with latex products; type of gloves; signs/symptoms suggestive of latex-related sensitization (LS) in and out of the hospital environment; signs/symptoms suggestive of atopy and food allergy.
RESULTS: A total of 326 questionnaires were evaluated (193 women and 133 men, aged between 30 and 73 years old). Out of this total, 75% of interviewees had up to 10-year length of service in their professions. The prevalence of signs/symptoms suggestive of sensitization to latex in the hospital environment, between the group of employees working in the Accounting Sector (therefore not exposed to latex in the workplace) and the remaining employees (exposed to latex products in their working environment) was significantly different (p<0.001). Also, the percentage of signs/symptoms suggestive of LS in the hospital environment was higher in subjects showing higher average time of use of gloves per day.
CONCLUSIONS: The present study demonstrated higher prevalence of signs/symptoms suggestive of LS among those workers exposed to latex products in the hospital environment and with higher contact time with any type of gloves. Therefore, it is clear the need to proceed with this research, for laboratorial confirmation of the latex-related sensitization, as well as that a proposal be submitted to the Institution towards the adoption of preventive measures regarding latex-related sensitization issue. Also, a consensus must exist to the fact that the health care workers comprise a population in risk for allergy to latex products.
Key words: ALERGY: latex; DISEASES: occupational; HYPER-SENSIBILITY: latex.
Y OBJETIVOS: Las referencias en la literatura sobre reacciones a los derivados
del látex han aumentado significativamente en los últimos años.
Sin embargo faltan datos de nuestro país relativos a la prevalencia de
sensibilidad al látex en los profesionales del área de la salud.
El objetivo de este estudio fue el de evaluar la prevalencia de señales/síntomas
sugestivos de sensibilidad al látex en profesionales del área de
MÉTODO: Después de aprobado por el Comité de Ética, se seleccionaron individuos pertenecientes a la plantilla de la institución: funcionarios del Sector de Limpieza, Contabilidad y División de Enfermería del Centro Quirúrgico; Médicos de Cirugía, Ginecología, Obstetricia, Anestesiología, Unidad de Terapia Intensiva y Clínica Médica. Después de recibir la información y consentir con la pesquisa, los individuos fueron sometidos a un cuestionario sobre: edad, sexo, categoría profesional; tipo y tiempo de contacto profesional con los derivados del látex; tipo de guante utilizado; señales/síntomas sugestivos de sensibilidad al látex dentro y fuera del ambiente hospitalario; señales/síntomas sugestivos de atopia y de alergia a alimentos.
RESULTADOS: Fueron evaluados 326 cuestionarios (193 mujeres y 133 hombres, con edad entre 30 y 73 años). Un 75% de los encuestados tenían 10 años de profesión. La prevalencia de los señales/síntomas sugestivos de sensibilidad al látex dentro del ambiente hospitalario con relación a los grupos compuestos por los funcionarios del Sector de Contabilidad (no expuestos a derivados del látex en el ambiente de trabajo), y el resto de los individuos (expuestos a derivados del látex en el ambiente de trabajo), evidenció una diferencia significativa (p < 0,001). El porcentaje de señales/síntomas sugestivos de sensibilidad al látex en el ambiente hospitalario fue más alto en los individuos con mayor tiempo promedio de uso de guantes por día.
CONCLUSIONES: Ese estudio mostró una mayor prevalencia de señales/síntomas sugestivos de sensibilidad al látex entre los profesionales expuestos a los derivados del látex en ambiente hospitalario y con un mayor tiempo de contacto con guantes de cualquier tipo. De esa forma, queda muy clara la necesidad de proseguir con esa investigación para la confirmación en laboratorio de la sensibilidad al látex, como también proponer a la Institución la adopción de medidas de prevención para la sensibilidad al látex. Debe haber una concientización de que profesionales del área de la salud constituyen una población de riesgo para alergia a los derivados del látex.
The latex is a fluid extracted mainly from the rubber tree Hevea brasiliensis, originated in the Amazon Region and constituted of polyisoprene, lipids, phospholipids and proteins 1.
The first reference to an allergic-type reaction to latex products is dated of 1933 2, and described a localized skin reaction. And the first reports on generalized urticaria, asthma and anaphylaxis were disclosed only in 1980 3,4 Since then, these reports are becoming increasingly common all around the world, showing a variable 2.9% to 73% incidence of reactions to latex products, depending on the population studied 5,6.
The proteins of both the natural and the processed latex constitute the allergens causing most of the reactions to latex product 7,8. Latex gloves are regarded as the main latex product causing increase of sensitization and no standard exists for its chemical constitution. The powder-containing latex gloves usually present with larger amounts of proteins and higher allergenic levels 7.
The main risk factors for these latex-related reactions are: atopia 4,7,9, some food-related allergies 6,10,11 and a history of multiple exposures to latex products 2,5,12-14.
These multiple exposures to latex products usually occur with workers using products in their field of activity (hairdressers, workers for food industry) or who handle latex and their pro-ducts 2, children experiencing neural tube disorders, specially meningomyelocele 5,13,14, patients undergone multiple surgical procedures and vesical catheters 2 and professionals and workers in the health care field 12,15,18.
Many hospital stuff and some products used specifically during anesthesia and surgery are latex-derived, therefore increasing the possibility of latex-related sensitization (LS) among health care professionals 12. In this group we include physicians, dentists, the nursing, nutrition and cleaning workers. Several researches have focused on checking the prevalence of latex-related allergic reactions among health professionals have used questionnaires about signs and suggestive symptoms of latex-related reactions or sensitization inside and outside the workplace, as well as of food-related allergies 16-20. In most of these researches, after questionnaires evaluation, the suspected latex-related or sensitization cases were referred to laboratorial tests, for diagnostic confirmation purposes. The results depicted a 0.5% to 24% variable LS prevalence 16,20. Among the anesthesiologists, the LS prevalence ranged from 12.5% to 15.8%, out of which 10.1% were asymptomatic and 24% presented contact or irritating dermatitis to latex products 2,15.
In Brazil, up to 1996, there were only a few reports on latex-related reactions 21,22. Since then, these figures are progressively increasing. Similar to what happened in other countries, it seems that we are at the beginning phase of the latex-related sensitization increase 7,23-35.
However, the Brazilian epidemiologic data on the prevalence of sensitization to latex products in health care workers are still scarce. This is the reason for the present research, with the objective of evaluating the prevalence of the latex-related suggestive history among health care workers.
Upon approval by the Ethics Committee on Research of the Hospital Central of Santa Casa de Misericordia de São Paulo, the research work started initially, selecting health care professionals from several areas of the Institution: accounting, cleaning, nursing division of the surgical center, physicians of the medical clinics, surgery, gynecology and obstetrics, anesthesiology service and intensive care unit (ICU).
After have being contacted the heads from each of the involved areas, the researchers met with different groups to explain the research to all professionals and to invite all those willing to participate, in a total of approximately 500 subjects.
Once a detailed explanation of the study it has being presented and an informed consent has being obtained from interested participants, the subjects were submitted to a standard questionnaire with questions about:
1. Age, gender, professional category;
2. Type and length of professional contact with latex products;
3. Type of glove used: for cleaning, for non sterile procedure, surgical, powder-containing or non-containing;
4. Signs and symptoms suggestive of sensitization to latex products within the hospital environment (clinical conditions, frequency, how long the reaction has started);
5. Signs and symptoms suggestive of atopia, food allergy and allergic reactions to the use of latex products extra-hospital (clinical conditions and frequency);
6. Signs or symptoms of allergic reactions while on medication; former jobs;
7. Number of former surgeries; intercurrences during former anesthetic-surgical act.
Excluded from the study were those professionals under anti-histaminic and/or chronic corticosteroid therapies and those who, for several reasons, did not perform their usual functions in the workplaces.
The selected population was assigned to two groups:
The Accounting Department employees, not exposed to latex products within the hospital environment and regarded as Control Group: CG;
The remaining participants regarded as exposed to latex products in the hospital environment and regarded as the Exposed Group: EG;
The statistical tests, namely: the Fisher Exact test (gender, signs/symptoms suggestive of LS out of the hospital, atopy, food allergy and use of cleaning gloves), the Chi-square test (use of surgical and procedure gloves), the Kruskal-Wallis test (age, length of service and time of use of gloves) and the median was applied in the descriptive analysis, once variables did not show a normal distribution.
In the analysis of the results regarding previous occurrences suggestive of atopia, possibility of LS at the workplace, food allergy and allergy to latex products used out of the hospital, it was considered:
Negative answer: absence of any sign/symptom or presence of only one sign/symptom reported only a few times 36.
Positive answer: presence of two or more signs/symptoms 36.
A statistically significant difference was defined for p < 0.05.
A total of 326 questionnaires were evaluated, involving 193 women and 133 men. Values related to age, length of time in the activity, time of use of gloves/day and number of surgical procedures performed were considered in median values, as they did not present a normal distribution (Table I).
As regards length of service variable, a substantial gap was noted between minimum and maximum values, but most of the interviewees (75%) were ranged between zero and 10 years length of service.
The former jobs, allergy signs/symptoms upon medication and inter-occurrences during the former anesthetic-surgical act variables were disregarded in the analysis of the results, as most of the interviewees from all sectors and professional categories involved (> 95%) did not answer to these questions.
Table II shows the distribution of the participants as regards professional category and the respective percentage to total amount.
A comparative analysis of the prevalence of signs/symptoms suggestive of LS within the hospital environment was carried out between the control group (CG) and the remaining of subjects regarded as exposed to latex products (EG) (Table III). A difference was found between groups (p < 0.001) with higher number of subjects experiencing signs/symptoms suggestive of LS within the hospital environment having occurred in the EG population.
Table IV shows the prevalence of subjects with and without signs/symptoms suggestive of LS within the hospital environment in relation to the several variables studied and the p value of the respective statistical analyses. All the interviewees reporting the use of procedure and surgical gloves mentioned the use of powder-containing latex gloves.
Figure 1 Percentage of Subjects with Signs/Symptoms Suggestive of LS in the Workplace According to their Professional Category.
In the analysis of the percentage of signs/symptoms suggestive of LS in the hospital environment and time of use of gloves per day (h) in relation to the professional category (Figure 2), it was noted that the groups presenting higher percentage of signs/symptoms suggestive of LS were those also presenting the larger average time of use of gloves.
Several studies estimate the costs involved in the latex-related allergy reaction as a work disease involving both the health care professionals who are restricted to perform their functions and the institutions 2,12,19,36,37. Said costs comprehend laboratory investigations, replacement of type of gloves used (powder-containing for non-containing gloves or for other material different from latex), change of equipment, installation of air conditioning special filters, transfer of involved employees to other workplaces and all resulting troubles thereto.
This issue has been underdisclosed in Brazil. Most of the studies do not regard latex-related allergy as a work disease, however there are reports or studies involving patients who experienced latex-related anaphylactic reactions 21-35.
There are two causes leading to latex-related reactions: allergic or immune (types I and IV hypersensitivity reactions) and non-allergic (irritating reactions). The type I hypersensitivity reaction is due to the sensitization to the latex proteins with clinical conditions varying from a localized edema to the anaphylactic shock and death 1,12. In the type IV reaction, the outcome is the contact dermatitis. The initial lesions are erythematous, papular and vesiculous, followed by epidermis desquamation and lichenification, with possible worsening of the skin condition. In atopic subjects, contact dermatitis leads to localized or anaphylactic reactions. This dermatitis may be latex-related, or caused by primary irritant agents used in the latex products fabrication or else by the powder present in the gloves 1,12. In the non-immune latex-related reaction the clinical picture is a skin reaction determined by the long standing and continuous contact with latex products. Once this exposure is eliminated, the symptomatology also disappears, but may arise again with a new exposure 1,12.
It is important to highlight that, even in the type IV and irritant reaction cases, if the condition is worsening, there may occur a skin disruption due to the acute or chronic dermatitis lesions, thus increasing the possibility of sensitization to the latex proteins and a posterior type I reaction.
In this study, although there were no lab tests to confirm latex-related sensitization, the results demonstrated a higher prevalence of signs/symptoms suggestive of this reaction among those professionals more exposed to latex products within the hospital environment (p < 0.001). These results are similar to those mentioned in the international literature and suggest the possible occurrence of LS dependent on the exposure level to latex products, mainly gloves, in the population studied 15,17,36,38,39.
In the present study, the use of gloves, either for procedures, surgery or cleaning, has always been related to the higher prevalence of professionals experiencing signs/symptoms suggestive of LS (p < 0.001). As regards the use of powder-containing and non containing gloves, all physicians and nurses used powder-containing gloves, which turned invalid the comparison carried out in several studies that concluded for the higher incidence of latex-related sensitization among users of powder-containing gloves 2,8,40,41. However, this fact (100% use of powder-containing gloves) demonstrates that the involved population is at higher risk for LS.
In addition, the group with higher prevalence of signs/symptoms suggestive of LS in the hospital environment has also shown difference as regards signs/symptoms suggestive of food allergy (p < 0.001), which is referred by different authors as latex-food cross sensitization 6,7,10,11,42.
The relationship between the group of health care professionals with possible LS and experiencing signs/symptoms suggestive of atopia has shown a significant difference, thus complying with the literature that mentions atopia as a risk factor for latex-related sensitization 4,7,17.
Up to the last decade, reusable gloves were used in Brazil, whereas in the USA and European countries the disposable gloves were used for much longer. It is known that the reusable gloves progressively lose the antigenic proteins due to the successive and repetitive cleaning and sterilization process 2. Therefore, in the present study involving an adult population, it is possible that the relationship between the number of former surgeries and the signs/symptoms of LS did not become evident, as many, or at least a few of these procedures may have occurred at the time when the reusable gloves were used, with lower LS incidence episodes. This finding is different from that found by authors dedicated to LS in children, particularly those pediatric patients experiencing neural tube malformation. These researchers concluded that the number of former surgical interventions was an important risk factor for LS, and highlighted the fact that in their studies the personnel involved used disposable gloves 5,13,14.
The health care professionals group possibly experiencing latex-related sensitization manifested higher prevalence of signs/symptoms suggestive of LS in the extra-hospital environment (p < 0.001), thus reinforcing the recommendation to make these professionals aware and refer them to a specialist.
The results reached at show the need to proceed with this study by adding laboratory tests for latex-related sensitization diagnosis confirmation purposes 9,43,44.
The present study did not aim at checking the prevalence of health care workers experiencing LS, because our Institution, as most of the Brazilian hospitals, did not have available the proper latex skin tests and radioimmunoassays. However, in spite of this limitation, the evaluation of the prevalence of signs/symptoms suggestive of latex-related sensitization, instead of the sensitization itself, serves as an alert to a problem not properly regarded in Brazil. Similarly to what is being done in other countries, the introduction and implementation of preventive measures as regards LS and the disclosure of the latex-related allergy as a work disease should be highly fostered 19,40-42,45.
01. Forte WCN, Neto FA, Mathias LAST - Reações anafiláticas ao látex. Diagnóstico e Tratamento, 2003;8:127-131. [ Links ]
03. Hirshman CA - Latex anaphylaxis. Anesthesiology, 1992;77:223-225. [ Links ]
04. Weiss ME, Hirshman CA - Latex allergy. Can J Anaesth, 1992;39:528-532. [ Links ]
05. Cremer R, Hoppe A, Kleine-Diepenbruck U et al - Natural rubber latex allergy: prevalence and risk factors in patients with spina bifida compared with atopic children and controls. Eur J Pediatr, 1998;157:13-16. [ Links ]
06. Blanco C, Carrillo T, Castillo R et al - Latex allergy: clinical features and cross-reactivity with fruits. Ann Allergy, 1994;73:309-314. [ Links ]
07. McFadden ER - Natural rubber latex sensitivity seminar: conference summary. J Allergy Clin Immunol, 2002;110:(Suppl2):S137-S140. [ Links ]
08. Yunginger JW, Jones RT, Fransway AF et al - Extractable latex allergens and proteins in disposable gloves and other rubber products. J Allergy Clin Immunol,1994;93:836-842. [ Links ]
09. Mathias LAST, Piccinini Filho L, Batti MAS - Reações Anafiláticas e Anafilactóides em Anestesia, em: Manica JT - Anestesiologia - Princípios e Técnicas. 3ª Ed, Porto Alegre, 2004, 1191. [ Links ]
10. Kim K, Hussain H, Beall G - Latex allergy and IgE antibodies to foods. J Allergy Clin Immunol, 1998;101:S208. [ Links ]
11. Levy DA, Mounedji N, Noirot C et al - Allergic sensitization and clinical reactions to latex, food and pollen in adult patients. Clin Exp Allergy, 2000;30:270-275. [ Links ]
12. Hamid RK - Latex allergy: diagnosis, management, and safe equipment. ASA Refresher Courses Anesthesiol, 1996;24:86-96. [ Links ]
13. Holzman RS - Clinical management of latex-allergic children. Anesth Analg, 1997;85:529-533. [ Links ]
14. Nieto A, Estornell F, Mazon A et al - Allergy to latex in spina bifida: a multivariate study of associated factors in 100 consecutive patients. J Allergy Clin Immunol, 1996;98:501-507. [ Links ]
15. Konrad C, Fieber T, Gerber H et al - The prevalence of latex sensitivity among anesthesiology staff. Anesth Analg, 1997;84:629-633. [ Links ]
16. Nettis E, Assennato G, Ferrannini A et al - Type I allergy to natural rubber latex and type IV allergy rubber chemicals in health workers with glove-related skin symptoms. Clin Exp Allergy, 2002;32:441-447. [ Links ]
17. Poole CJ, Nagendran V - Low prevalence of clinical latex allergy in UK health care workers: a cross-sectional study. Occup Med, 2001;51:510-512. [ Links ]
18. Sussman GL, Liss GM, Deal K et al - Incidence of latex sensitization among latex glove users. J Allergy Clin Immunol, 1998;101:171-178. [ Links ]
19. Potter PC, Crombie I, Marian A et al - Latex allergy at Groote Schuur Hospital prevalence, clinical features and outcome. S Afr Med J, 2001;91:760-765. [ Links ]
20. Swanson M, Zakharov S, Luss L et al - Latex aeroallergen quantification in hospitals of Moscow, Russia. Ann Allergy Asthma Immunol, 2001;87:307-310. [ Links ]
21. Goudouris E, Machado M, Prado E - Hipersensibilidade ao látex. Rev Soc Bras Alerg Imonol, I 1993;16:32-34. [ Links ]
22. Mathias LAST, López S, Domenico MSD et al - Reação anafilática ao látex. Rev Bras Anestesiol, 1995;45:(Supp):275. [ Links ]
23. D'Ottaviano CR, Marques EL, Umezu LRC - Reação anafilática ao látex em paciente pediátrico portador de bexiga neurogênica. Relato de caso. Rev Bras Anestesiol, 1999;49:(Supp):CBA122. [ Links ]
24. Mathias LAST, Piccinini Filho L, Acquati GF et al - Sensibilidade ao látex. Relato de caso. Rev Bras Anestesiol, 1999;49:(Supp):CBA119. [ Links ]
25. Miyoshi E, Soares SI, Sucheck JSC et al - Alergia ao látex: complicação anestésica cada vez mais freqüente. Relato de casos. Rev Bras Anestesiol, 1999;49:(Supp):CBA108. [ Links ]
26. Spindola MAS, Gomes HP, Mazzuco RM et al - Reação anafilática ao látex no transoperatório. Relato de caso e conduta diagnóstica. Rev Bras Anestesiol, 2000;50:(Supp):98B. [ Links ]
27. Linde H, Fernandes AC, Allarcon JB et al - Distúrbios na formação do tubo neural e alergia ao látex. Rev Bras Anestesiol, 2001;51:(Supp):177B. [ Links ]
28. Moreira MD - Sobre um caso de anafilaxia em profissional de saúde. JBM, 2002;82:44-5. [ Links ]
29. Cerqueira BGP, Kraychete DC, Filho JAL et al - Alergia ao látex. Relato de caso. Rev Bras Anestesiol, 2003;53:(Supp):155B. [ Links ]
30. Freitas WLS, Carraretto AR, Montebeller F et al - Reação ao látex durante anestesia em paciente paraplégico. Relato de caso. Rev Bras Anestesiol, 2003;53:(Supp):157A. [ Links ]
31. Oliveira GS, Gomes DBG, Pimentel LG - Alergia ao látex. Relato de caso. Rev Bras Anestesiol, 2003;53:(Supp):156A. [ Links ]
32. Soares ISC, Suchek JSC, Simões CM - Manifestações intra-operatórias da sensibilização ao látex. Relato de caso. Rev Bras Anestesiol, 2003;53:(Supp):156B. [ Links ]
33. Higushi ST, Slikta Filho J, Imperatriz PC et al - Anestesia para paciente com alergia ao látex. Relato de caso. Rev Bras Anestesiol, 2004;54:(Supp):209B. [ Links ]
34. Spindola MA, Almeida C, Mazzucco RM et al - Choque anafilático causado pelo látex no intra-operatório. Relato de caso. Rev Bras Anestesiol, 2004;54:179B. [ Links ]
35. Spindola MA, Pinheiro JT, Mazzucco RM et al - Identificação do agente causal, após reação alérgica intra-operatória. Relato de caso. Rev Bras Anestesiol, 2004;54: (Suppl): 180B. [ Links ]
36. Liss GM, Sussman GL, Brown S et al - Latex allergy: epidemiological study of 1351 hospital workers. Occup Environ Med, 1997;54:335-342. [ Links ]
37. Vandenplas O, Jamart J, Delwiche JP et al - Occupational asthma caused by natural rubber latex: outcome according to cessation or reduction of exposure. J Allergy Clin Immunol, 2002;109:125-30. [ Links ]
38. Brown R, Schauble J, Hamilton R - Prevalence of latex allergy among anesthesiologists: identification of sensitized but asymptomatic individuals. Anesthesiology, 1998;89:292-299. [ Links ]
39. Steiner DJ , Schwager RG - Epidemiology, diagnosis, precautions, and policies of intraoperative anaphylaxis to latex. J Am Coll Surg, 1995;180:754-761. [ Links ]
40. Edelstam G, Arvanius L, Karlsson G - Glove powder in the hospital environment consequences for healthcare workers. Int Arch Occup Environ Health, 2002;75:267-271. [ Links ]
41. Tarlo SM, Easty A, Eubanks K et al - Outcomes of a natural rubber latex control program in an Ontario teaching hospital. J Allergy Clin Immunol, 2001;108:628-633. [ Links ]
42. Mitakakis TZ, Tovey ER, Yates DH et al - Particulate masks and non-powdered gloves reduce latex allergen inhaled by healthcare workers. Clin Exp Allergy 2002;32:1166-1169. [ Links ]
43. Hamilton RG, Adkinson NF - Diagnosis of natural rubber latex allergy: multicenter latex skin testing efficacy study. Multicenter Latex Skin Testing Study Task Force. J Allergy Clin Immunol, 1998;102:482-490. [ Links ]
44. Anonymous. Task Force on Allergic Reactions to Latex. American Academy of Allergy and Immunology. Committee report. J Allergy Clin Immunol 1993;92:16-18. [ Links ]
Dra. Lígia Andrade da Silva Telles Mathias
Alameda Campinas, 139/41
01404-000 São Paulo, SP
for publication 10 de junho de 2005
Accepted for publication 09 de Janeiro de 2006
* Received from CET/SBA, Serviço de Anestesiologia da Irmandade Santa Casa de Misericórdia de São Paulo (ISCMSP), São Paulo, SP.