Permanent vascular access in patients with end-stage renal disease, Brazil
Acesso vascular permanente em pacientes renais crônicos terminais no Brasil
Acceso vascular permanente en pacientes renales crónicos terminales en Brasil
Gisele Macedo da SilvaI; Isabel Cristina GomesII; Eli Iola Gurgel AndradeI; Eleonora Moreira LimaIII; Francisco de Assis AcurcioIV; Mariângela Leal CherchigliaI
IDepartamento de Medicina Preventiva e Social. Faculdade de Medicina (FM). Universidade Federal de Minas Gerais (UFMG). Belo Horizonte, MG, Brasil
IIDepartamento de Estatística. Instituto de Ciências Exatas. UFMG. Belo Horizonte, MG, Brasil
IIIDepartamento de Pediatria. FM-UFMG. Belo Horizonte, MG, Brasil
IVDepartamento de Farmácia Social. Faculdade de Farmácia. UFMG. Belo Horizonte, MG, Brasil
Correspondence | Correspondência
OBJECTIVE: To assess factors associated with the establishment of permanent vascular access for patients with end-stage renal disease.
METHODS: Cross-sectional study conducted in a nationally representative sample of Brazilian end-stage renal disease patients in dialysis and transplant centers during 2007. The sample comprised only patients who received hemodialysis as a primary therapy modality and reported the type of vascular access for their primary hemodialysis treatment (N=2,276). Data were from the TRS Project - "Economic and Epidemiologic Evaluation of Modalities of Renal Replacement Therapy in Brazil". Multiple logistic regression analysis was used to assess factors associated with the establishment of permanent vascular access in these patients.
RESULTS: About 30% of the patients studied had an arteriovenous vascular access. The following factors were associated with a lower likelihood of having an arteriovenous vascular access as a primary type of access: time of hemodialysis start since the diagnosis of chronic renal failure < 1 year; shorter dialysis therapy; having no private health insurance; living in the central-western, northeastern and southeastern regions of Brazil; and living in the northern region plus having no private health insurance. In the final model there was found a positive association between the outcome and pre-dialysis care and no were association with socioeconomic and comorbidity variables.
CONCLUSIONS: The study results showed that the focus should on pre-dialysis care to increase the establishment of an arteriovenous vascular access before starting hemodialysis in Brazil.
Descriptors: Arteriovenous Fistula. Health Services Accessibility. Renal Dialysis, instrumentation. Renal Insufficiency, Chronic. Cross-Sectional Studies.
OBJETIVO: Analisar fatores associados à provisão de acesso vascular arteriovenoso no Brasil.
MÉTODOS: Estudo transversal, nacionalmente representativo, com pacientes com doença renal crônica terminal acompanhados em serviços de diálise ou em centros transplantadores no ano de 2007. A amostra incluiu apenas pacientes que tiveram a hemodiálise como primeira modalidade de tratamento e que sabiam com que tipo de acesso vascular haviam iniciado o tratamento (N = 2.276). Os dados são oriundos do Projeto TRS - "Avaliação econômico-epidemiológica das modalidades de Terapia Renal Substitutiva no Brasil". Regressão logística múltipla foi utilizada.
RESULTADOS: Aproximadamente 30% dos pacientes tinham acesso vascular arteriovenoso. Os fatores associados à baixa probabilidade de ter acesso vascular arteriovenoso como primeiro tipo de acesso foram: tempo de diagnóstico de doença renal crônica anterior à entrada em hemodiálise < 1 ano, menor tempo de tratamento dialítico, não possuir cobertura de plano de saúde, residir na região Centro-Oeste, Nordeste e Sudeste, e residir na região Norte e ao mesmo tempo não possuir cobertura de plano de saúde. No modelo final não foi observada associação do desfecho com variáveis socioeconômicas e comorbidades, mas sim com cuidados pré-diálise.
CONCLUSÕES: Os resultados mostram que, para aumentar a provisão de acesso vascular arteriovenoso antes do início da hemodiálise no Brasil, os esforços devem ser focados no cuidado pré-diálise.
Descritores: Fístula Arteriovenosa. Acesso aos Serviços de Saúde. Diálise Renal, instrumentação. Insuficiência Renal Crônica. Estudos Transversais.
OBJETIVO: Analizar factores asociados a la provisión de acceso vascular arteriovenoso en Brasil.
MÉTODOS: Estudio transversal, nacionalmente representativo, con pacientes con enfermedad renal crónica terminal acompañados en servicios de diálisis o en centros transplantadores en el año de 2007. La muestra incluyó pacientes que tuvieron la hemodiálisis como primera modalidad de tratamiento y que sabían con que tipo de acceso vascular habían iniciado el tratamiento (N=2.276). Los datos son oriundos del Proyecto TRS - "Evaluación económica-epidemiológica de las modalidades de Terapia renal Sustitutiva en Brasil". Fue utilizada la regresión logística múltiple.
RESULTADOS: Aproximadamente 30% de los pacientes tenían acceso vascular arteriovenoso. Los factores asociados a la baja probabilidad de tener acceso vascular arteriovenoso como primer tipo de acceso fueron: tiempo de diagnóstico de enfermedad renal crónica anterior a la entrada en hemodiálisis < 1 año, menor tiempo de tratamiento dialítico, no poseer cobertura de seguro de salud, residir en la región Centro-Oeste, Noreste y Sureste, y residir en la región Norte y al mismo tiempo no poseer cobertura de seguro de salud. En el modelo final no fue observada asociación del resultado con variables socioeconómicas y co-morbilidades, pero si con cuidados pre-diálisis.
CONCLUSIONES: Los resultados muestran que para aumentar la provisión de acceso vascular arteriovenoso antes del inicio de la hemodiálisis en Brasil, los esfuerzos deben ser enfocados en el cuidado pre-diálisis.
Descriptores: Fístula Arteriovenosa. Accesibilidad a los Servicios de Salud. Diálisis Renal, instrumentación. Insuficiencia Renal Crónica. Estudios Transversales.
The establishment of an arteriovenous vascular access before hemodialysis is the ideal option to treat patients with end-stage renal disease (ESRD)5 as it is associated with better metabolic control and more favorable clinical outcomes.8 The vascular access should be created in patients within three to six months of an anticipated need for dialysisª and it has been considered an adequate pre-dialysis care measure.8,14 A permanent vascular access for hemodialysis (HD) includes an autologous arteriovenous fistula (AVF) or alternatively an arteriovenous graft when suitable veins are not available.3,ª The establishment of an access requires attempts and preparation for the surgical procedure that may take weeks or even months before the actual cannulation process.2 In emergencies, a temporary central venous catheter (CVC) allows rapid access for HD.3,a However, it has higher risk of complications such as infection and thrombosis.1,10,13 In addition, temporary CVC provides a lower blood flow rate,11 thus limiting the effectiveness of HD.ª
In Brazil dialysis centers of the Sistema Único de Saúde (SUS - National Public Health System) have a protocol of establishing an arteriovenous vascular access as early care.b However, according to data from the Brazilian Society of Nephrology in 2008, 66% of the patients who started HD using catheters had their treatment started without previous preparation by health providers. And patients later referred to a nephrologist are also likely to start dialysis using a temporary catheter.19 There has been no national study to assess factors associated with the establishment of permanent vascular access in Brazil. This study aimed to assess factors associated with this procedure in ESRD patients.
The present study is part of a large cross-sectional study, the "TRS Project - Economic and Epidemiologic Evaluation of Modalities of Renal Replacement Therapy in Brazil," conducted by the Universidade Federal de Minas Gerais Health Economics Research Group from January to May 2007.
Patients were recruited from 81 dialysis and 17 transplant centers accredited by the Brazilian Nephrology Society whose main databases were available to the public health sector. The sample was representative of the national Brazilian population. A total of 3,036 patients who had undergone renal replacement therapy were interviewed using structured questionnaires by previously trained interviewers. Information on socioeconomic and demographic characteristics as well as on quality of life was collected. The patients' satisfaction level was also assessed. All patients selected were 18 years old or more diagnosed with ESRD and were either on dialysis for at least three months or were at least six months post-kidney transplant. Patients who had multiple transplants were excluded from the study. A stratified two-stage cluster sample was applied and sampling units were: renal replacement therapy services and patients. Only patients who had HD as a primary dialysis modality were enrolled (2,276 subjects) in the present study. The statistical power of the sample was 99.9%.
Hypothesis testing to compare proportions and error probability was applied to verify the sample power before the study. The prevalence of arteriovenous fistula used in this formula was described in international studies.14
The response variable was the primary type of vascular access used for hemodialysis in each patient (arteriovenous vascular access including arteriovenous fistula and arteriovenous graft; or temporary CVC). The explanatory variables included age, gender, income, education level, skin color, city, region of residence, private health insurance coverage and clinical variables (time of HD start since the diagnosis of chronic renal failure [CRF] and presence of diabetes mellitus and hypertension before HD). All variables with "do not know" answers were considered as having "missing" information.
The descriptive analysis included measure of frequency distribution and central tendency. The association between response and explanatory variables was assessed by univariate logistic regression and those variables with p < 0.20 were included in the multiple model. The odds ratio (OR) was used to assess power analysis and its related 95% confidence interval (95% CI).
The relevance of each variable included in the multiple model was verified by the Wald test, and those variable with no significant contribution were removed. The adjustment of the final model was verified by comparing it with other similar models through the likelihood-ratio test, as well as by the Hosmer-Lemeshow goodness-of-fit test. The final model included variables with p < 0.05. The interaction between the variables in the final model was also tested. Thus, based on the algorithm, the probability of occurrence was estimated. The analyses were performed using the software R version 2.7.2.
The study was approved by the Research Ethics Committee of the Universidade Federal de Minas Gerais in 2004 (ETIC 0397/04). All subjects and renal replacement therapy centers were asked to sign a consent form prior to their participation in the study.
Among the 2,276 patients studied, 1,466 were on HD therapy at the time of the interview, 351 were on peritoneal dialysis and 459 had kidney transplantation. Their mean age was 49 years (SD = 14.4). The average monthly income, reported by 2,205 patients, was US$ 400.5 (SD = US$ 680.9), approximately 2.4 times the monthly minimum wage in Brazil at the time. The mean duration of dialysis therapy reported by 2,173 patients was 4.88 years (SD = 4.47) (Table 1).
Of the patients studied, 31% had arteriovenous vascular access for HD as a primary access, while 69% had temporary CVC. The univariate analysis showed lower rates of permanent vascular access associated with younger age; education level < 11 years; low income; dark skin color; living in capital cities; and living in any region other than southern Brazil. Having no private health insurance, absence of diabetes or hypertension before diagnosis, time of HD start since the diagnosis of CRF < 1 year and shorter dialysis therapy were also associated factors (Table 2).
Four factors were associated with low establishment of permanent vascular access in the multiple logistic regression: time of HD start since the diagnosis of CRF < 1 year; shorter dialysis therapy; having no private health insurance; and living in the northeastern, central-western or southeastern regions.
A multiplicative interaction between having no private health insurance and the region of residence was identified. Thus, the final model included the following variables: time of HD start since the diagnosis of CRF < 1 year; shorter dialysis therapy; having no private health insurance; living in the northeastern, central-western or southeastern regions and living in the northern region combined with having no private health insurance (Table 3). The Hosmer-Lemeshow test result was 0.347.
Those patients diagnosed with CRF one year before starting HD were 3.4 times more likely to start therapy with a temporary CVC. The increment of one year of treatment increased the likelihood of having an arteriovenous vascular access. Having no private health insurance increased that likelihood of starting therapy with a temporary vascular access to almost 1.56. Patients living in the southeastern, central-western and northeastern regions were 1.6, 2.6 and 2.9 more likely to use a temporary CVC as a primary access for HD, respectively. Those patients living in the northern region who did not have private health insurance were 4.3 times more likely to start treatment with a temporary vascular access.
There were identified five socioeconomic and clinical factors associated with lower likelihood of arteriovenous vascular access as primary type of access for HD in Brazil: time of HD start since the diagnosis of CRF < 1 year; shorter dialysis therapy; having no private health insurance; living in the northeastern, central-western or southeastern regions; and living in the northern region and having no private health insurance. Stehman-Breen et al21 (2000) reported that 35% of the patients selected from dialysis centers in the US had permanent access at the beginning of therapy, and those who had been informed about their illness earlier were more likely to have permanent access at the beginning of HD therapy. This reflects proper pre-dialysis care.4 An early diagnosis of chronic renal disease allows enough time to the patient to accept a vascular access and to prepare it, as well as to detect and correct any inadequacy in the maturation process. Pre-dialysis care includes not only care provided by a nephrologist, but also patient education by other health providers.
Although the effect of early care provided by nephrologists was not investigated in our study, Stehman-Breen et al21 study also showed that more visits to the nephrologist before starting HD increased the likelihood of establishing a permanent access prior to therapy. In United States, Arora et al4 (1999) and Astor et al5 (2001) concluded that a delayed referral of patients to a nephrologist negatively affected the establishment of permanent vascular access in primary HD. This finding points out the importance of nephrologist care.
Arora et al4 (1999) also found that a substantial number of patients seen earlier by nephrologists still had catheters at the beginning of treatment. It suggests that adequate preparation of patients with ESRD requires referral to a nephrologist at an even earlier time point in the course of chronic renal disease, and requires a multidisciplinary team for pre-dialysis care (generalists, nurses and providers), not only nephrologists.
Patients with health insurance coverage were more likely to have an arteriovenous vascular access before primary HD. This finding may be explained by the fact that private health service include outpatient access7 and regular medical visits.12 According to Mendoza-Sassi & Béria,12 (2003) Brazilian patients with private insurance coverage were 80% more likely to have regular medical attention.
Ribeiro et al17 (2006) found that SUS users seek more medical care in emergency services and suggested that these units are the first to provide care to these patients. For patients with ESRD, it is not ideal. Ongoing care is necessary and should promote early referral of patients to establish a permanent vascular access before hemodialysis.
The duration of dialysis therapy was associated with the establishment of an arteriovenous vascular access in the present study. It is possible that patients starting treatment at different time points are subject to different care practices or have access to different services. Also, changes in the epidemiological profile of patients such as aging, higher rates of diabetes and cardiovascular diseases, can occur over time and offset the improvements in patient care.9
The region of residence also influenced the likelihood of establishing permanent vascular access for HD. One possible explanation for regional differences is greater concentration of medical doctors, particularly specialists, in certain regions. For example, 80% of nephrologists have their practices in the southeastern and southern regions.11 This discrepancy in the distribution of medical doctors may be attributed to different economic development of Brazilian regions and more availability of medical residence and better working and employment conditions in these regions.15
However, in the present investigation, it is not clear why patients from the southeastern region had less permanent access as compared to those in the southern region. Ribeiro et al17 (2006) found that patients from the southern region are more likely to use SUS services than those from southeastern Brazil.
Differences in the provision of dialysis and preparation of vascular access were reported throughout the UK,6 but they could not be entirely explained based on age and/or ethnic groups, thereby suggesting the influence of other factors such as service capacity and/or practice standard.6 Although almost half of HD services in Brazil are located in the southeastern region,20 it seems that they are not sufficiently effective. Travassos et al22 (2006) found a lower utilization of public health services in the northern, northeastern and central-western than in the southeastern region.
Regional differences in the establishment of vascular access associated with not having private health insurance can be explained by differences in the proportion of patients who have private health insurance within each region. The multiplicative interaction of the variables having no private health insurance and region of residence showed a better fitting model. Patients living in the northern region who did not have private insurance were significantly less likely to start HD with permanent vascular access. Ribeiro et al17 (2006) have previously reported this gap in the proportion of SUS users with and without private health insurance in each region: 21:1 and 15:1 in the northeastern and northern regions, respectively.
The present study has some limitations. First, its cross-sectional design does not allow any causal inference. The findings should be interpreted as associations since exposure and outcome occurred simultaneously. A prevalence bias may have occurred due to selection into or out of the study population: patients who were not successful in getting primary permanent vascular access or died before HD start were less likely to participate in the study. In addition, the variables were self-reported and thus subject to recall bias. However, the dichotomization of the variables skin color and time of HD start since the diagnosis and the inclusion of duration of dialysis therapy may have reduced the chance of error. Other important variables such as time of referral to a nephrologist and potential problems while establishing an arteriovenous vascular access were not investigated.
Variables usually associated with permanent vascular access,1,16 such as dark skin color, age, income, education level and presence of comorbidities including diabetes mellitus and hypertension, were not statistically significant in the multiple analysis. In the final model, the factors associated with failure to establish an arteriovenous vascular access for all ESRD patients were mainly related to pre-dialysis care. Therefore, given the increasing number of patients on HD in Brazil,20 it is important to implement a care program to ESRD patients that includes establishing an adequate arteriovenous access prior to HD, which in turn may be cost-effective and ultimately improve these patients' quality of life.18,23 Further investigations are needed to explore the characteristics of dialysis services that may influence establishing a permanent vascular access for HD.
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Correspondence | Correspondência:
Gisele Macedo da Silva
Avenida Alfredo Balena, 190
30130-100 Belo Horizonte, MG, Brasil
Research supported by Fundo Nacional de Saúde/Ministério da Saúde (Process Nº 4864/2005) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq - Process Nº 409729/2006-0).
Article based on the Master's dissertation by Silva GM presented at Universidade Federal de Minas Gerais in 2009.
The authors state that there are no conflicts of interest.
a National Kidney Foundation. 2006 Updates clinical practice guidelines and recommendations. New York;2006 [citado 2009 ago]. Disponível em: http://www.kidney.org/professionals/kdoqi/pdf/12-50-0210_JAG_DCP_Guidelines-VA_Oct06_SectionC_ofC.pdf
b Ministério da Saúde. Portaria nº 432 de 6 de junho de 2006. [citado 2009 out]. Diario Oficial Uniao. 7 jun 2006; Seção 1.