Tasa de filtración glomerular medida y estimada (Parte II). Ajuste a superficie corporal / Measured and estimated glomerular filtration rate (Part II). Adjustment to body surface area

Una pérdida de la mitad de la masa renal no necesariamente tendrá la mitad de la tasa de filtración glomerular (TFG), es decir, no hay una correlación exacta entre la reducción de masa renal y la pérdida de función renal. La (TFG) es un índice necesario para diagnóstico, seguimiento de pacientes con deterioro de la función renal, chequeos epidemiológicos, ajuste de dosis de drogas nefrotóxicas o de eliminación renal, estadificación de la enfermedad renal crónica, etc

Loss of half renal mass does not necessarily correspond to half of glomerular filtration rate (GFR), meaning that there is not an exact correlation between renal mass reduction and loss of renal function. The GFR is a necessary index for: diagnosis; follow-up of patients with renal injury; epidemiological controls; nephrotoxic drugs dose adjustment or renal elimination drugs; chronic renal disease stratification, etc

Tasa de filtración glomerular medida y estimada. Numerosos métodos de medición (Parte I) / Measured and estimated glomerular filtration rate. Numerous methods of measurements (Part I)

Una pérdida de la mitad de la masa renal no necesariamente tendrá la mitad de la TFG, es decir, no hay una correlación exacta entre la reducción de masa renal y la pérdida de función renal. La tasa de filtración glomerular (TFG) es un índice necesario para diagnóstico, seguimiento de pacientes con deterioro de la función renal, chequeos epidemiológicos, ajuste de dosis de drogas nefrotóxicas o de eliminación renal, estadificación de la enfermedad renal crónica, etc.En esta actualización se analiza brevemente los principales métodos utilizados con el fin de estimar el filtrado glomerular, algunas de sus fortalezas y debilidades. El empleo de la tasa de filtración glomerular estimada en estudios epidemiológicos ha contribuido a generar controversias de envergadura que más que resultar en un avance científico, han producido larguísimas discusiones como producto de sofismas y desvíos por estos cálculos.Debería replantearse el aplicar ecuaciones de estimación de la TFG en estudios de laboratorio en la población, dada la imperfección de las mismas y a las dificultades en la interpretación de los resultados para el médico clínico no especialista en la materia.

The loss of half the renal mass does not necessarily imply half the Glomerular Filtration Rate (GFR), meaning that there is not an exact correlation between renal mass reduction and renal function loss. GFR is a necessary index for diagnosis and to establish chronic renal disease stages, followup of renal failure patients, epidemiological studies, adjustment of nephrotoxic drugs or renal excretion drugs, among other uses.This update briefly analyzes the principal methods used in order to estimate glomerular filtration, some of its strengths and weaknesses.The use of estimated GFR in epidemiological studies has contributed to generate a wide scale of controversies that instead of contributing to scientific progress, have produced endless discussions because of misleading argumentations and deviations for these calculations.Equations applied for estimating GFR in population studies, should be reconsidered, given their imperfection and the difficulty for clinicians, who are not specialists on the subject, to interpret the results.

Initial Glomerular Filtration Rate and Survival in Hemodialysis. The role of permanent vascular access

Background: A significant increase in the number of patients starting chronic hemodialysis (HD) with an estimated glomerular filtration rate (eGFR)≥10mL/min/1.73m2 was observed in Argentina between 2004 and 2009. Methods: In order to study this topic, we calculated the mortality hazard ratios (HR) in a cohort of incident HD individuals from the Argentine Registry of Chronic Dialysis [Registro Argentino de Diálisis Crónica] (2004-2009), grouped according to the initial eGFR (0-4.9, 5-9.9, 10-14.9 and ≥15mL/min/1.73m2 ; reference group 0-4.9) estimated by CKD-EPI; in three cohorts: "total population", "healthy (<65 years, without diabetes or comorbidities) and "planned entry" (with permanent vascular access). Results: After adjusting the population (n=16,931) for age, gender, coexisting conditions, serum albumin, income, and temporary vascular access a HR of 1.19 (95%CI:1.07-1.33) was observed in the group with eGFR≥15mL/min/1.73m2. In the cohort of 3,897 "healthy" after adjusting for the same co-variates, HRs of 1.44 (95%CI: 1.08-1.65) and 1.65 (95%CI: 1.06-2.55) were obtained for the groups with baseline eGFR values of 10-14.9 and ≥15mL/min/1.73m2, respectively. In "planned entry" patients (n=6,280), after adjusting for age, gender, co-morbidities, serum albumin and income, HRs in all groups were not significantly different as compared to the control group. Conclusions: HD initiation with eGFR>10mL/min/1.73m2 shows no survival advantage. The higher mortality in the group with >eGFR starting dialysis looks like an "artifact" related to higher age, more co-morbidities, low albuminemia and the use of temporary vascular access (AU)

Antecedentes: Entre 2004 y 2009, se observó en Argentina un aumento significativo del número de pacientes que iniciaban un tratamiento crónico de hemodiálisis (HD) con una tasa de filtrado glomerular estimada (TFGe) ≥ 10 ml/min/1,73 m2. Métodos: Para su estudio, calculamos las razones de riesgo (RR) de mortalidad en una cohorte de individuos incidentes en HD del Registro Argentino de Diálisis Crónica (2004-2009), que se agrupó, en función de la TFG inicial estimada por CKD-EPI (0-4,9; 5-9,9; 10-14,9; y ≥ 15 ml/min/1,73 m2, siendo 0-4,9 el grupo de referencia), en tres cohortes: "población total", "cohorte sana" (< 65 años sin diabetes ni ningún tipo de comorbilidad) y "cohorte con entrada prevista" (con acceso vascular permanente). Resultados: Tras ajustar los datos de la población (n = 16 931) en función de la edad, el sexo, las enfermedades coexistentes, la albúmina sérica, los ingresos y la existencia de un acceso vascular temporal, se observó una RR de 1,19 (95 % IC: 1,07-1,33) en el grupo con una TFGe ≥ 15 ml/min/1,73 m2. En la cohorte formada por 3897 individuos "sanos", se obtuvieron, tras ajustar las mismas covariables, unas RR de 1,44 (95 % IC: 1,08-1,65) y 1,65 (95 % IC: 1,06-2,55) para los grupos con TFGe iniciales de 10-14,9 y ≥ 15 ml/min/1,73 m2, respectivamente. En los pacientes con "entrada prevista" (n = 6280), tras ajustar los resultados en función de la edad, el sexo, la comorbilidad, el nivel de albúmina sérica y los ingresos, las RR de todos los grupos no difirieron significativamente de las del grupo de control. Conclusiones: Iniciar el tratamiento de HD con una TFGe > 10 ml/min/1,73 m2 no revela ninguna ventaja de supervivencia. La mayor mortalidad del grupo con mayor TFGe que inicia la diálisis es un "artefacto" que está relacionado con una mayor edad, la existencia de más comorbilidades, la hipoalbuminemia y el uso de accesos vasculares temporales (AU)

Initial glomerular filtration rate and survival in hemodialysis. The role of permanent vascular access.

BACKGROUND: A significant increase in the number of patients starting chronic hemodialysis (HD) with an estimated glomerular filtration rate (eGFR)≥10 mL/min/1.73 m(2) was observed in Argentina between 2004 and 2009. METHODS: In order to study this topic, we calculated the mortality hazard ratios (HR) in a cohort of incident HD individuals from the Argentine Registry of Chronic Dialysis [Registro Argentino de Diálisis Crónica] (2004-2009), grouped according to the initial eGFR (0-4.9, 5-9.9, 10-14.9 and ≥15 mL/min/1.73 m(2) ; reference group 0-4.9) estimated by CKD-EPI; in three cohorts: "total population", "healthy" (<65 years, without diabetes or comorbidities) and "planned entry" (with permanent vascular access). RESULTS: After adjusting the population (n=16,931) for age, gender, coexisting conditions, serum albumin, income, and temporary vascular access a HR of 1.19 (95%CI:1.07-1.33) was observed in the group with eGFR≥15 mL/min/1.73 m(2). In the cohort of 3,897 "healthy" after adjusting for the same co-variates, HRs of 1.44 (95%CI: 1.08-1.65) and 1.65 (95%CI: 1.06-2.55) were obtained for the groups with baseline eGFR values of 10-14.9 and ≥15 mL/min/1.73 m(2), respectively. In "planned entry" patients (n=6,280), after adjusting for age, gender, co-morbidities, serum albumin and income, HRs in all groups were not significantly different as compared to the control group. CONCLUSIONS: HD initiation with eGFR>10 mL/min/1.73 m(2) shows no survival advantage. The higher mortality in the group with >eGFR starting dialysis looks like an "artifact" related to higher age, more co-morbidities, low albuminemia and the use of temporary vascular access.

The lack of income is associated with reduced survival in chronic haemodialysis.

INTRODUCTION: Poor socioeconomic status in the patient population is one of the causes of the lack of primary and secondary prevention of chronic kidney disease and negatively affects the survival of patients on chronic haemodialysis (HD). OBJECTIVE: To confirm whether the low or absent income of the incident population on HD is a factor of poor prognosis. METHODS: We used the incident HD population of the Argentine Registry of Chronic Dialysis. Follow-up lasted 12 months, performing an intention to treat analysis. We applied the Cox model to assess the association between income and survival of patients after adjusting for age, sex, diabetes, comorbidities, initial laboratory results, and first vascular access. RESULTS: We analysed 13466 adult patients (age at onset: 60.4 ± 15.6 years; 57.2% were male, and 39.2% diabetic) who were assigned to 2 groups: 1) "no income" group, 5661 patients (age at onset: 60.3 ± 15.4 years; 53.1% were male and 41.4% diabetic), 2) "with income" group, 7805 patients (age at onset, 60.5 ± 15-8] years; 60.1% were male and 37.5% diabetic). The "no income" group had a hazard ratio of 1.19 (95% confidence interval [CI]: 1.11-1.28) in the univariate analysis, 1.23 (95% CI: 1.14-1.32 ) considering age and gender, 1.22 (95% CI: 1.13-1.31) by adding diabetes mellitus, 1.26 (95% CI: 1.18-1.36) by adding comorbidities, 1.25 (95% CI: 1.16- 1.35) by adding the initial laboratory results, and 1.24 (95% CI: 1.15- 1.33) if temporary vascular access is included. All models resulted in a significance of P=.000. CONCLUSIONS: Low or no income of patients at the time of entry into HD is an independent risk factor for immediate lower survival.

La falta de ingresos económicos se asocia a menor supervivencia en hemodiálisis crónica / The lack of income is associated with reduced survival in chronic haemodialysis

Introducción: Las pobres condiciones socioeconómicas de la población es uno de los causales de la falta de prevención primaria y secundaria de la enfermedad renal crónica e influiría negativamente en la sobrevida de los pacientes en hemodiálisis (HD) crónica. Objetivo: Confirmar si el bajo o nulo ingreso económico de la población incidente en HD es un factor de mal pronóstico vital. Métodos: Utilizamos la población incidente en HD del Registro Argentino de Diálisis Crónica. El seguimiento fue de 12 meses, realizándose un análisis por intención de tratar. Se aplicó el Modelo de Cox para evaluar la asociación entre ingresos económicos y la sobrevida de los pacientes ajustando por edad, sexo, diabetes, comorbilidades, laboratorio inicial y primer acceso vascular. Resultados: Analizamos 13.466 pacientes adultos (edad al inicio: 60,4 [±15,6] años, 57,2% varones, 39,2% diabéticos) que fueron asignados a 2 grupos: 1) «Sin ingresos», 5.661 pacientes (edad al inicio: 60,3 [±15,4] años, 53,1% varones, 41,4% diabéticos); 2) «Con ingresos», 7.805 pacientes (edad al inicio: 60,5 [±15,8] años, 60,1% varones, 37,5% diabéticos). «Sin ingresos» mostró un hazard ratio de 1,19 (intervalo de confianza [IC] 95%: 1,11-1,28) en el univariado; de 1,23 (IC 95%: 1,14-1,32) considerando edad y género; de 1,22 (IC 95%: 1,13-1,31) agregando diabetes mellitus; de 1,26 (IC 95%: 1,18-1,36) agregando comorbilidades; de 1,25 (IC 95%: 1,16-1,35) adicionando laboratorio inicial y de 1,24 (IC 95%: 1,15-1,33) si se incluye acceso vascular transitorio. En todos los modelos la significación resultó en una p = 0,000. Conclusiones: Los bajos o nulos ingresos económicos del paciente en el momento del ingreso a HD es un factor de riesgo independiente de menor sobrevida inmediata (AU)

Introduction: Poor socioeconomic status in the patient population is one of the causes of the lack of primary and secondary prevention of chronic kidney disease and negatively affects the survival of patients on chronic haemodialysis (HD). Objective: To confirm whether the low or absent income of the incident population on HD is a factor of poor prognosis. Methods: We used the incident HD population of the Argentine Registry of Chronic Dialysis. Follow-up lasted 12 months, performing an intention to treat analysis. We applied the Cox model to assess the association between income and survival of patients after adjusting for age, sex, diabetes, comorbidities, initial laboratory results, and first vascular access. Results: We analysed 13466 adult patients (age at onset: 60.4 ±15.6 years; 57.2% were male, and 39.2% diabetic) who were assigned to 2 groups: 1) "no income" group, 5661 patients (age at onset: 60.3 ±15.4 years; 53.1% were male and 41.4% diabetic), 2) "with income" group, 7805 patients (age at onset, 60.5 ±15-8] years; 60.1% were male and 37.5% diabetic). The "no income" group had a hazard ratio of 1.19 (95% confidence interval [CI]: 1.11-1.28) in the univariate analysis, 1.23 (95% CI: 1.14-1.32 ) considering age and gender, 1.22 (95% CI: 1.13-1.31) by adding diabetes mellitus, 1.26 (95% CI: 1.18-1.36) by adding comorbidities, 1.25 (95% CI: 1.16- 1.35) by adding the initial laboratory results, and 1.24 (95% CI: 1.15- 1.33) if temporary vascular access is included. All models resulted in a significance of P=.000. Conclusions: Low or no income of patients at the time of entry into HD is an independent risk factor for immediate lower survival (AU)

Sobrevida en diálisis crónica en Argentina: período 2004-2008 / Survival in chronic dialysis in Argentina: period 2004-2008

Se presenta la sobrevida según método de Kaplan-Meier(KM) de pacientes incidentes (01/04/2004 al 31/12/2008) al Registro Argentino de Diálisis Crónica (DC). El seguimiento (N=27.224) tuvo un máximo de 2101 días o 69.07 meses, en ese período fallecieron 9747 pacientes y al 31/12/2009 estaban con vida 10319 pacientes. La mediana de sobrevida fue de 47,9 meses. Se recurrió al Modelo del riesgo proporcional de Cox multivariado para determinar riesgo relativo o Hazard Ratio (HR) entre cada variable independiente al ingreso a DC. Del total de variables tomamos 29 (siempre que no entren en conflicto entre ellas y con casos perdidos <25%). 19 variables se muestran como predictoras significativas : Edad al ingreso (4,1% de mayor riesgo de muerte por cada año), presencia de: Insuficiencia Cardíaca, Angina Persistente o Infartos de Miocardio previos, Enfermedad Cerebrovascular, Insuficiencia Vascular Periférica, Virus C de la Hepatitis+, Arritmia Cardíaca, haber recibido Transfusiones en los últimos 6 meses, Enfermedad Pulmonar Crónica, Neoplasia al ingreso y ser portador de SIDA.

Características de la población incidente en diálisis crónica en Argentina / Characteristics of the incident hemodialysis population in chronic hemodialysis in Argentina

Evaluamos las características de la población incidente en Diálisis Crónica (DC) en Argentina desde 2004 hasta 2008. La tasa de incidencia del total del país fue en 2008 de 143.1 pacientes por millón de habitantes-año (ppm), con cambios significativos entre los años 2006, 2007 y 2008. Existe una gran dispersión de tasas entre provincias de Argentina con un rango de 71-201 ppm. La edad de la población fue envejeciendo significativamente llegando en 2008 a 59.8 años de promedio y aumentando significativamente la población mayor a 64 años, especialmente en varones, cuyas tasas duplican a la de las mujeres a partir de los 70 años. La Nefropatía Diabética es la primer causa de Incidencia a DC representando el 35,5% del total en 2008, en aumento permanente desde 2004. Las comorbilidades cardiovasculares disminuyeron en el tiempo, no obstante se continúa con altos porcentajes. El 67% de los pacientes presentan Hematocrito menor al 30%. El 52% de los pacientes inician DC con Albuminemia menor a 3.5 gramos / decilitros. El 1.4-2.0% de la población ingresa con presencia del anticuerpo de la Hepatitis C. Llegan sin vacunarse contra la Hepatitis B el 61% de los pacientes, con aumento significativo en los años transcurridos. Aumentó la población que comienza Hemodiálisis Crónica (HD) con catéter transitorio, llegando a 2008 a representar el 66% del total. La población que declara no poseer ingresos económicos disminuyó al 22% en 2008. Concluimos que es de importancia fundamental el seguimiento o monitoreo anual de estas variables iniciales en pacientes incidentes en DC porque muchas de ellas demostraron estar directamente relacionadas con peor pronóstico vital.

A new prognostic index for one-year survival in incident hemodialysis patients.

PURPOSE: Although scoring comorbidities for patients beginning chronic hemodialysis has proved significant and has led researchers to develop several indexes, none of them has been extensively accepted. The aim of this study was to: 1) develop a prognostic index for patients entering renal replacement therapy; and 2) identify which one of the available scores better predicts one-year survival. METHODS: Records from 5,360 incident dialysis-requiring ESRD individuals were studied and a novel comorbidity index (NI) was developed. The agreement of this NI with the Charlson age-comorbidity, Kahn-Wright, ACPI, and Hemmelgarn indexes was assessed to identify which one better predicts one-year survival. The Cox proportional hazard regression with time-dependent covariates was used to analyze survival and the area under the receiver operating characteristic (ROC) curve was calculated to assess the ability of this score to discriminate between prognoses and to compare this NI with indexes already in use. RESULTS: 16 of the original 19 predictor variables displayed hazard ratios =1.2. Although the area under the ROC curves for all the indexes compared were significantly different from 0.5, the NI showed better performance characteristics (0.74 vs. 0.70 for Charlson's, 0.68 for ACPI, 0.67 for Khan-Wright's and 0.63 for Hemmelgarn's). Compared with the Charlson score, the z statistic was 7.78 (p<0.001). One-year survival estimate for the high-risk group was 43% with the NI and ranged from 66% to 72% when assessed through other indexes. CONCLUSIONS: We recommend the use of this NI because it better predicts the one-year survival probability of incident hemodialysis-requiring ESRD individuals.

La estimación del filtrado glomerular: [revisión] / The estimation of glomerular filtration rate: [review]

La tasa de filtración glomerular es utilizada para: detección(diagnóstico y prevalencia), evaluación (progresión de la enfermedad renal, complicaciones y riesgo cardiovascular), manejo (terapéutica, inicio de terapia substitutiva renal, medicaciones y procedimientos). Las ecuaciones de estimación del filtrado glomerular emplean algunos datos demográficos o antropométricos y ademas el dosaje de Creatinina o Cistatina en sangre. Estas sustancias deberían ser analizadas con técnicas calibradas y estandarizadas.(AU)

La estimación del filtrado glomerular: [revisión] / The estimation of glomerular filtration rate: [review]

La tasa de filtración glomerular es utilizada para: detección(diagnóstico y prevalencia), evaluación (progresión de la enfermedad renal, complicaciones y riesgo cardiovascular), manejo (terapéutica, inicio de terapia substitutiva renal, medicaciones y procedimientos). Las ecuaciones de estimación del filtrado glomerular emplean algunos datos demográficos o antropométricos y ademas el dosaje de Creatinina o Cistatina en sangre. Estas sustancias deberían ser analizadas con técnicas calibradas y estandarizadas.

End-stage renal disease and its treatment in Latin America in the twenty-first century.

The Latin American Society of Nephrology and Arterial Hypertension's Dialysis and Transplant Registry was chartered in 1991. It collects information on ESRD and its treatment in 20 countries of the region. The prevalence of patients on renal replacement therapy (RRT) increased from 129 pmp in 1992 to 447 pmp in 2004; in 2004, 56% of the patients were on hemodialysis, 23% on peritoneal dialysis, and 21% had a functioning kidney graft. The highest rates of prevalence were reported in Puerto Rico (1027 pmp), Chile (686 pmp), and Uruguay (683 pmp). Hemodialysis was widely used, except in El Salvador, Mexico, Guatemala, Nicaragua, and the Dominican Republic, where peritoneal dialysis predominated. Incidence rate increased from 27.8 pmp to 147 pmp in the same period of observation; the lowest rate was reported in Guatemala (11.4 pmp) and the highest in Puerto Rico (337.4 pmp). Diabetes mellitus was the leading cause of renal failure in incident patients; the highest rates were reported in Puerto Rico (62.2%) and Mexico (60%). Forty-four percent of the incident population were older than 65 years. Access to renal replacement therapy was universal in Argentina, Brazil, Chile, Cuba, Puerto Rico, Uruguay, and Venezuela, while was restricted in other countries. Main causes of death in dialysis were cardiovascular (44%) and infectious disease (26%). The rate of renal transplantation increased from 3.7 pmp in 1987 to 14.5 in 2004; fifty-three percent of the organs came from cadavers. Overall, donation rate was 5.9 pmp. In conclusion, the prevalence and incidence rates have increased over the years, and diabetes mellitus has emerged as the leading cause of kidney disease in the region. Although the rate of kidney transplantation has increased, the number remains insufficient to match the growing demand. The implementation of renal health programs in the region is urgently needed.

The Latin American Dialysis and Transplantation Registry (RLDT) annual report 2004.

INTRODUCTION: The Latin American Dialysis and Transplantation Registry (RLDT) includes 20 national affiliates. Data are provided annually by delegates designated by the national affiliate or by the Registry's Coordinating Committee. RESULTS: Prevalence of persons on renal replacement therapy (RRT) has increased from 192 patients per million population (pmp) in 1992 to 424 pmp in 2003, a 10% annual increment. Fifty-six percent were on hemodialysis, 23% on peritoneal dialysis, and 21% had a functioning graft. The highest prevalence was observed in Puerto Rico, and the lowest in Ecuador. Hemodialysis was the preferred treatment modality, except in El Salvador, Mexico, and Guatemala. Incidence rates varied widely; they were high in Puerto Rico (336 pmp) and Mexico (275 pmp) and low in Costa Rica (24 pmp) and Ecuador (14 pmp). Diabetes was the main reported cause of endstage renal disease (ESRD); it caused from 21% (Uruguay) to 65% (Puerto Rico) of cases. Forty percent of incident patients were > 65 years old. Access to RRT is universal in Argentina, Brazil, Cuba, Puerto Rico, Uruguay, and Venezuela but restricted in countries like Mexico and Paraguay. Main causes of death on dialysis were cardiovascular (44%) and infection (26%). Transplantation rates increased from 3.7 pmp in 1987 to 13.7 pmp in 2003, mostly from living donors (55%). The number of transplants reached 69,181 grafts. CONCLUSION: Prevalence of RRT has increased over the years; diabetes has become the main cause of ESRD, and cardiovascular disease is the leading cause of death on dialysis. Transplantation rates, although increasing, have not matched the growing population on dialysis. Programs to promote renal health in the region are urgently needed.

The Latin American Dialysis and Renal Transplantation Registry Annual Report 2002.

Latin America is a conglomerate of adjacent countries having in common a Latin extraction and language (Spanish or Portuguese) and exhibiting extreme variations in socioeconomic status. The Latin American Society of Nephrology and Hypertension Dialysis and Renal Transplantation Registry was created in 1991. Annual data are sent by local societies in 3 forms: patient, center, and country. The prevalence of renal replacement therapy (RRT) (all modalities) increased from 119 patients per million population (pmp) in 1991 to 349 pmp in 2001; the acceptance rate was 91.7 pmp in 2001. Dialysis prevalence was 277 pmp; hemodialysis was the predominant modality, except in Mexico (86% on peritoneal dialysis). The highest dialysis prevalence and acceptance rates were reported by Puerto Rico, Uruguay, and Chile. Among incident patients, diabetic nephropathy (33%) and nephroangioesclerosis (32%) were the primary causes; 38% were older than 65 years old. Renal transplants increased from 3.7 pmp in 1987 to 13.7 pmp in 2001. In 2003, 6357 transplants were performed (55% living donor); the cumulative number performed since 1987 reached 55,947. Prevalence and incidence are low because not all patients with end-stage renal disease have access to RRT because of restricted availability, difficulties in referral, and inequities in coverage. The annual increase in the number of patients on RRT (8%-10%) is higher, proportionally, than the annual growth of the Latin American population in general (1.5%). Efforts must be focused on prevention and treatment of chronic kidney disease, especially in diabetic and older patients, and in implementing better organ donation programs to improve the pool of cadaveric donors.