Appendix to dialysis centre guidelines: recommendations for the relationship between outpatient haemodialysis centres and reference hospitals. Opinions from the Outpatient Dialysis Group. Grupo de Trabajo de Hemodiálisis Extrahospitalaria.

INTRODUCTION: The different clinical guidelines backed by the Spanish Society of Nephrology (SEN) attempt to homogenise the monitoring of renal patients. However, this effort to homogenise treatment has been obstructed in the case of renal replacement therapy patients on haemodialysis due to, among other reasons, the existence of several different dialysis providers, with private centres located in many cities, each with their own reference hospitals and different criteria for treatment based on the existing outsourcing services agreements with the public health service, which also differ between regions. A good relationship between a private dialysis centre and its reference hospital would lead to equal treatment for all dialysis patients, at least at that particular town. The SEN, through the efforts of the Grupo de Trabajo de Hemodiálisis Extrahospitalaria (Outpatient Haemodialysis Group), has prioritised a close relationship and good communication between reference hospitals and dialysis centres in order to guarantee proper continuity of the health care given to these patients. STRATEGIES FOR IMPROVEMENT: Conditions for referring patients from one centre to another. A patient that starts a haemodialysis programme should be referred from a reference hospital with a definitive vascular access for optimising treatment, with a full report updated within 24-48 hours before the transferral, including essential information for providing proper nephrological treatment: primary pathology, recent viral serology (including hepatitis B and C virus [HBV and HCV] and human immunodeficiency virus [HIV]), parameters for anaemia and calcium-phosphorus metabolism, and ions, date of the first session of dialysis, and the number and dates of blood transfusions received. Furthermore, patients referred from the dialysis centre to the hospital, whether for programmed visits or emergency hospitalisation, should be accompanied by an updated report indicating the primary diagnoses, recent events, viral serology and laboratory analyses, updated haemodialysis and treatment regimens used, and the reason for transferral to the hospital. A single, digital clinical history that is accessible by both institutions would facilitate this situation, although this option is not completely available to all centres and hospitals. There are also legal issues to resolve in this aspect. Continued care for dialysis patients. Good communication between dialysis centres and hospitals is fundamental for achieving a proper level of care for dialysis patients, and not only with the nephrology department. The interconsultations of dialysis patients at each private centre, as well as the requests for diagnostic tests, should be able to be requested by the centre directly. The results and reports from these interconsultations should also be sent to the centre. It would also be best if the reference hospitals and their private dialysis centres shared common treatment protocols. These protocols should include basic aspects of the treatment of renal patients (anaemia, mineral metabolism, vascular accesses including catheter infections, etc., and laboratory tests), transplant protocols, complementary tests, and other components specific to each area. Not only would this generalise and unify the approach taken with dialysis patients regardless of where they are treated, it would also facilitate access to data on all patients regarding clinical trials and research studies. Access to medication. Dialysis patients require medications that are only given in the hospital setting, which is normally provided by the reference hospital, as per the agreement between institutions. It would also be recommendable that any other medications not included in the agreement (antibiotics, urokinase, nutritional supplements, etc.) be dispensed in a similar manner. Access to kidney transplant. The management of the transplant waiting list, once a patient starts renal replacement therapy, should be controlled from the dialysis centre, as in any other procedure. As such, the nephrologists from each centre should be familiar with the existing protocols and new developments in this context, and should participate in meetings with nephrology and urology departments in each hospital. The transplant protocol at each town/region should be followed for all patients, whether dialysis is undergone in a hospital or private centre. Characteristics of the work at dialysis centres. The doctor attending patients at each dialysis centre must be a specialist in nephrology. This complicated issue must be a requirement for agreements within the regional health system in order to guarantee a proper and equitable treatment of patients that receive dialysis in private centres. Only in the case of an absence of a nephrologist should a general practitioner be used, and this doctor must have adequate training in haemodialysis. This training should also be standardised. Over 75% of nephrologists that work at these centres are alone during the workday, and 40% never see another colleague during the whole shift. The administrators of these centres should seek out protocols that provide professional contact, both with the hospital staff and nephrologists from other centres, which would facilitate an exchange of ideas. Training. The nephrologists at each centre have the right and the obligation to perform research and to continuously expand their training, so as to develop and improve health care provision. Since the majority of patients in haemodialysis programmes are treated in outpatient centres that depend on reference hospitals, we might suggest a minimal rotation of nephrology residents in private outpatient dialysis centres, once accreditation has been given for providing this training.

[Investigation into the relationship between outpatient haemodialysis centres and referring hospitals in Spain]. / Encuesta sobre la relación existente entre centros de hemodiálisis extrahospitalarios y hospitales de referencia en España.

INTRODUCTION: To guarantee continuity and equity in the clinical assistance of patients on hemodialysis in extrahospitalary centers (EC) a close relationship and a good level of communication between them and their reference hospitals (RH) is essential. The aim of this study was to assess the present situation of this relationship in our country (Spain) so as to be able to detect improvement opportunities. METHODS: Descriptive and transversal study using two self-report anonymous surveys: one for EC (81 questions) and one for RH (56 questions) sent by e-mail to all Spanish EC and RH registered in the Spanish Society of Nephrology. RESULTS: We received answers from 80 EC and 30 RH. 70% of the EC were managed by multinational companies; only 16 % EC were placed in a hospital. 64% of the EC need to employ non-nephrological medical staff. Nearly 40% of the EC nephrologists also go on duty at their RH. More than three quarters of the EC nephrologists are alone during their workday. Bidirectional telephone communication is very frequent between EC and RH. Around a third of the patients sent from RH to EC arrive without current viral serology and/or without a functioning vascular access. Most of the patients sent from EC to RH bring an up-to-date complete medical report. 41,3 % of the EC answered that they were usually consulted by their RH doctor colleagues about decisions to be taken regarding their patients. Routine blood and other medical protocol tests of CE are well defined in the formal agreement with their RH in 65 % of the cases, although they can be modified by the EC through consensus with the RH in more than 50 % of the cases. 60 % of the EC can directly consult other specialists in the RH but more than 50 % need to do so through the RH nephrologist. Parenteral medication used in the ECs is mostly supplied by their RH, but a third of ECs have some limitations with uncommon or not concert-specified parenteral drugs. RHs refer that most of the vascular accesses are done in the hospital, whereas ECs say that this is true only in half of the cases. More than a third of the fistulae of predialysis patients are done in the ECs as part of their collaboration with RHs. The majority of ECs can share the decision about patients' inclusion in renal transplant waiting list. In only a fifth of the cases is there a common database between CE and RH, and less than half share common protocols or objectives. 62,5% of CEs participate with RHs in clinical trials. More than half of the dialysis private companies provide continuous training and education to their ECs personnel, either directly through the company or facilitating assistance to courses or congresses. CONCLUSIONS: Some of the relationship aspects that appear to be clearly improvable are: CEs nephrologist solitude and their limited access to continuous training and education, an adequate referral of the patients from the RHs, CEs nephrologist's autonomy at making consultations to specialists or their limitations when asking for hospital medications. A closer relationship between CEs and RHs is of the utmost importance in guaranteeing continuity and equity in the clinical assistance of our hemodialysis patients. The creation of a debate forum would favour discussion and common resolution of such aspects.

[Spanish extrahospitalary hemodialysis centers survey]. / Encuesta sobre los centros de hemodiálisis extrahospitalaria en España.

BACKGROUND: Many guides and scientific recommendations about hemodialysis (HD) treatment have been developed. However, its impact and application is unknown. The aim of this study is to describe how Spanish Extrahospitalary Hemodialysis Centers work. METHODS: A transversal, descriptive study was conducted by means of a survey. An 83-items questionnaire tackled different aspects involving patients and HD characteristics, Dialysis Unit organization and anemia management. RESULTS: One hundred surveys were distributed and 91% were answered, corresponding to 6599 patients (M 4015/F 2584). Fifteen % were younger of 50 years and 45.2% older of 70 years. Seventy seven % had arteriovenous fistulas, 8.1% had polytetrafluoroethylene grafts and 14.8% had catheters. The mean number of patients per center was 72.3 (11-212). Seventy eight % were divided in 3 shifts, with a mean relationship of 38.9 patients/physician, 4.7 patients/nurse and 9 patients/auxiliary personnel. HD characteristics were: 60.1% of the HD sessions were longer than 4 hours, 97.2% were on a 3 days/week schedule; 95.4% used a conventional technique; 49.1% were performed with high-flux membranes, 89.6% with synthetic membranes, and 11.7% used Qb higher than 400 mL/min: On the other hand, 8.8% of the patients were HVC +, 0.68% were AgHBs +, and 0.09 were HIV +. There were HCV + patients in 79% of Dialysis Units, 50% of them with complete isolation, while patients with hepatitis B were attended in 13.8%, and VIH + in 3.4% of the Units, the latter always with complete isolation. Water treatment was done with simple osmosis in 46.6% of the cases, with water collection in 86.8% with pyrogen filter in the monitors in 48.9%. Surveillance of the controls was performed by the physician in 94.3% of the cases, and by technicians or nurses in the rest. Mean Hb was 11.9(1.4) g/dL, being higher of 11 g/dL in 80.2% of the patients. Ferritin higher than 100 microg/L was found in 92.4% and transferrin saturation higher than 20% in 81.9% of patients. The percentage treated with erithropoyetic stimulant agents was 90.6%. CONCLUSIONS: All information collected is relevant in order to know what is done and how to improve it.. It will be useful to evaluate the impact of the publication of the new Guides of HD Centers of SEN on medical practice in this area.

Encuesta sobre los centros de hemodiálisis extrahospitalaria en España / Spanish extrahospitalary hemodialysis centers survey

Introducción: Existen múltiples guías y recomendaciones científicas sobre el tratamiento de HD, pero se desconoce su grado de aplicación y repercusión. El Grupo de Trabajo de Hemodiálisis Extrahospitalaria se planteó describir una serie de puntos relevantes de la forma de trabajo de los centros extrahospitalarios. Material y métodos: Se realizó un estudio transversal y descriptivo, mediante un cuestionario de 83 preguntas en forma de encuesta, que abordaba distintos aspectos de los pacientes (pac), de características la HD (pauta, tratamiento de agua, medidas de aislamiento de virus), de la organización y el manejo de la anemia. Resultados: Se distribuyeron encuestas a 100 centros, de los que respondieron el 91%. El número total de pacientes fue 6.599 (H 4.015 vs M 2584). El 15,7% eran menores de 50 y el 45,2% mayores de 70 años. Los accesos vasculares prevalentes eran: 77% fístulas nativas, 8,1% prótesis y el 14,8% catéteres. La media de pacientes por centro fue 72,3 (rango 11-212), en el 78% divididos 3 turnos, con una media 38,9 pac/médico, 4,7 pac/enfermera y 9 pac/auxiliar. El 60,1% se dializaban más de 4 horas, con una frecuencia de 3 días/semana en el 97,2%, por una técnica convencional el 95,4%, con membranas de alta permeabilidad el 49,1% y sintéticas el 89,6%, el 11.7% utilizaban Qb superiores a 400 mL/min. El 8,8% de los pacientes eran VHC+, 0,68% virus B + y 0,09 VIH +. El 79% de los centros dializaban pacientes portadores del virus C (con aislamiento completo el 50%), mientras que los individuos virus B + se atendían en el 13,8% y los HIV + en el 3,4% de los centros, siempre con aislamiento completo. El tratamiento de agua fue ósmosis simple en el 46,6%, con almacenamiento de agua, 86,8% y filtro de pirógenos en los monitores, 48,9%. La supervisión de los controles la realizaba el médico en el 94,3% y en el resto sólo lo supervisaban el técnico o el personal de enfermería. La hemoglobina media fue 11,9 (1,4) g/L, siendo superior a 11 g/L en el 80,2% de los pacientes, con una ferritina > 100 μg/L el 92,4% y una saturación > 20% el 81,9%. El % de tratados con agentes estimuladores de la eritropoyesis era el 90,6%. Conclusiones: Toda la información obtenida es relevante para conocer qué se hace y cómo mejorarlo. Además, proporciona una herramienta para evaluar el impacto de la publicación de la Guía de Centros de HD de la SEN sobre la práctica médica en este sector

Background: Many guides and scientific recommendations about hemodialysis (HD) treatment have been developed. However, its impact and application is unknown. The aim of this study is to describe how Spanish Extrahospitalary Hemodialysis Centers work. Methods: A transversal, descriptive study was conducted by means of a survey. An 83-items questionnaire tackled different aspects involving patients and HD characteristics, Dialysis Unit organization and anemia management. Results: One hundred surveys were distributed and 91% were answered, corresponding to 6,599 patients (M 4,015/F 2,584). Fifteen % were younger of 50 years and 45.2% older of 70 years. Seventy seven % had arteriovenous fistulas, 8.1% had polytetrafluoroethylene grafts and 14.8% had catheters. The mean number of patients per center was 72.3 (11-212). Seventy eight % were divided in 3 shifts, with a mean relationship of 38.9 patients/physician, 4.7 patients/nurse and 9 patients/auxiliary personnel. HD characteristics were: 60.1% of the HD sessions were longer than 4 hours, 97.2% were on a 3 days/week schedule; 95.4% used a conventional technique; 49.1% were performed with high-flux membranes, 89.6% with synthetic membranes, and 11.7% used Qb higher than 400 mL/min: On the other hand, 8.8% of the patients were HVC +, 0.68% were AgHBs +, and 0.09 were HIV +. There were HCV + patients in 79% of Dialysis Units, 50% of them with complete isolation, while patients with hepatitis B were attended in 13.8%, and VIH + in 3.4% of the Units, the latter always with complete isolation. Water treatment was done with simple osmosis in 46.6% of the cases, with water collection in 86.8% with pyrogen filter in the monitors in 48.9%. Surveillance of the controls was performed by the physician in 94.3% of the cases, and by technicians or nurses in the rest. Mean Hb was 11.9(1.4) g/dL, being higher of 11 g/dL in 80.2% of the patients. Ferritin higher than 100 μg/L was found in 92.4% and transferrin saturation higher than 20% in 81.9% of patients. The percentage treated with erithropoyetic stimulant agents was 90.6%. Conclusions: All information collected is relevant in order to know what is done and how to improve it. It will be useful to evaluate the impact of the publication of the new Guides of HD Centers of SEN on medical practice in this area

[Functional dependency evaluation of hemodialysis patients: a multicentric study]. / Valoración del grado de dependencia funcional de los pacientes en hemodiálisis (HD): estudio multicéntrico.

BACKGROUND: There has been a change in the hemodialysis population characteristics over the last years with a progressive increase in patient,s age and associated comorbility and mortality. This older hemodialysis population are more functionally and medically dependent increasing the time taken to perform nursing work. The objective of this study was to evaluate the degree of functional dependency on hemodialysis patients and the need of care by nursing workload. METHODS: A transversal descriptive study was done during 1 month (april 2005) on 586 patients from 10 HD Units in Spain. No exclusion criteria were used. The Delta Test, who was used to evaluate the patients dependency needs, is a workload measure instrument base on three subscales: dependency, Physical Deficiency and mental deficiency. The indicators are measure on a scale of one to three with each level representing an increasing demand on nursing time. The results obtained from the Delta Test were analyzed taking into account the following variables: age, average time in dialysis, Charlson comorbidity Index, geographic location and HD unit. RESULTS: 46% of the patients show some degree of dependency, of these 12.8% were moderated and 8.1% severe; the subscale analysis showed that 19.6% and 6.7% had, respectively, a moderate to severe physical and mental health deficiency. The dependency degree varied significantly between HD Units and geographic location with a range of 0% to 59.8%. The degree of dependency were statistically associated with age and CCI. The higher CCI (r: 0,21; p < 0.001) and age (r: 0,26; p < 0.001) the higher was the Delta Test Score for dependency level. Patients times of initiation on dialysis were not associated with an increase in the degree of dependency. The aspects evaluated by the Delta Test that showed a higher score were those related to patients mobility. The patients assistance requirements during the HD session are basically related to a lack of mobility due to musculoskeletal disease and to a lesser extent to behavior alterations. CONCLUSIONS: HD units are attending patients with an important degree of dependency which impose and added workload to the healthcare personnel. In occasions, it is very difficult to attend and give proper care with the current legally established nurse to patient ratio which. This suggests the need to implement a better staffing policy. The Delta Test provides an objective, adaptable and standardized instrument for measuring degree of dependency of HD patients.

Valoración del grado de dependencia funcional de los pacientes en hemodiálisis (HD): estudio multicéntrico / Functional dependency evaluation of hemofialysis patients. A multicentric study

Introducción: Las características de los pacientes que se incluyen en hemodiálisis (HD) han cambiado en los últimos años, habiendo aumentado la edad y la comorbilidad, lo que tiene implicaciones sobre aspectos funcionales, dada la necesidad de ayuda que requieren estos pacientes. El objetivo de este estudio ha sido analizar el grado de dependencia funcional del paciente en HD. Métodos: Estudio transversal y descriptivo en 586 pacientes dializados en abril de 2005 en 10 unidades de HD ubicadas en la Comunidad Valenciana, Andalucía y Castilla-León. Para valorar el grado de dependencia se utilizó el «Test Delta», que consta de tres subescalas que miden: Dependencia: (puntuación máxima 30), Deficiencia física: (puntuación máxima 15) y Deficiencia psíquica: (puntuación máxima 15). Los ítems se puntúan de 0 a 3, de menor a mayor severidad. Se analizaron los resultados obtenidos de acuerdo con las siguientes variables: Edad, tiempo medio en hemodiálisis, Índice de Comorbilidad de Charlson (ICC), Provincias y Unidades. Resultados: El 45,6% de los pacientes presentaba algún tipo de dependencia (un 12,8% en grado moderado y un 8,1% en grado severo). El análisis por sub-escalas mostró una Deficiencia física moderada-severa en el 19,6%, y en el 6,7% una Deficiencia psíquica. Este grado de dependencia variaba significativamente de unas unidades a otras (0%- 59,8%), y según áreas geográficas. La edad y el ICC mostraron asociación estadísticamente significativa con el grado de dependencia, de modo que a mayor edad (r: 0,26; p < 0,001) y mayor puntuación en el ICC (r: 0,21; p < 0,001) mayor grado de dependencia, sin embargo el tiempo de permanencia en hemodiálisis no mostró asociación. Los aspectos evaluados en el Test Delta que mostraron mayor puntuación fueron los relacionados con la movilidad del paciente. Los requerimientos de ayuda se deben fundamentalmente a falta de autonomía en la movilidad por alteraciones del aparato locomotor y, en menor medida, a trastornos de conducta. En conclusión, los centros de hemodiálisis están atendiendo a pacientes con un importante grado de dependencia, lo que supone una mayor carga de trabajo para el personal sanitario y muy especialmente el de enfermería. En ocasiones es imposible atender a este tipo de pacientes con el ratio de personal asignado actualmente por los conciertos vigentes, y se requiere una mayor dotación de enfermería. La existencia de parámetros que de manera objetiva permitan valorar tales circunstancias, hacen aconsejable aprobar un instrumento de valoración común, que sea sencillo, universal y rápido en la valoración y que, además, pueda adaptarse a las necesidades cambiantes de la población a la que va destinado

Background: There has been a change in the hemodialysis population characteristics over the last years with a progressive increase in patient,s age and associated comorbility and mortality. This older hemodialysis population are more functionally and medically dependent increasing the time taken to perform nursing work. The objective of this study was to evaluate the degree of functional dependency on hemodialysis patients and the need of care by nursing workload. Methods: A transversal descriptive study was done during 1 month (april 2005) on 586 patients from 10 HD Units in Spain. No exclusion criteria were used. The Delta Test, who was used to evaluate the patients dependency needs, is a workload measure instrument base on three subscales: dependency, Physical Deficiency and mental deficiency. The indicators are measure on a scale of one to three with each level representing an increasing demand on nursing time. The results obtained from the Delta Test were analyzed taking into account the following variables: age, average time in dialysis, Charlson comorbidity Index, geographic location and HD unit. Results: 46% of the patients show some degree of dependency, of these 12.8% were moderated and 8.1% severe; the subscale analysis showed that 19.6% and 6.7% had, respectively, a moderate to severe physical and mental health deficiency. The dependency degree varied significantly between HD Units and geographic location with a range of 0% to 59.8%. The degree of dependency were statistically associated with age and CCI. The higher CCI (r: 0,21; p < 0.001) and age (r: 0,26; p < 0.001) the higher was the Delta Test Score for dependency level. Patients times of initiation on dialysis were not associated with an increase in the degree of dependency. The aspects evaluated by the Delta Test that showed a higher score were those related to patients mobility. The patients assistance requirements during the HD session are basically related to a lack of mobility due to musculoskeletal disease and to a lesser extent to behavior alterations. Conclusions: HD units are attending patients with an important degree of dependency which impose and added workload to the healthcare personnel. In occasions, it is very difficult to attend and give proper care with the current legally established nurse to patient ratio which. This suggests the need to implement a better staffing policy. The Delta Test provides an objective, adaptable and standardized instrument for measuring degree of dependency of HD patients

The PTH-calcium relationship during a range of infused PTH doses in the parathyroidectomized rat.

To establish the PTH dosage that maintains normal mineral homeostasis in the PTX rat, a series of doses of rat 1-34 PTH were infused via a subcutaneously implanted miniosmotic pump. The doses were 0, 0.011, 0.022, 0.044, and 0.11 microg/100 g/hour. After 48 hours, serum calcium ranged from 5.56 +/- 0.02 to 16.29 +/- 0.25 mg/dl, ANOVA P < 0.001, and serum phosphorus from 12.49 +/- 0.03 to 5.33 +/- 0.34 mg/dl, ANOVA P < 0.001. By post hoc test, the serum calcium level was different (P < 0.05) at every PTH dose; the serum phosphorus level was different (P < 0.05) at every PTH dose except between the two highest doses. The PTH dosage that produced a normal serum calcium (10.09 +/- 0.10 mg/dl) and phosphorus (6.90 +/- 0.18 mg/dl) was 0.022 microg/100 g/hour. The relationship between increasing doses of PTH and both serum calcium and phosphorus was curvilinear and the calcium-phosphorus product was remarkably constant from a serum calcium of 7-13 mg/dl. The increase in serum calcium and the decrease in serum phosphorus were more rapid at lower than at higher PTH doses so that for both, an asymptote was reached. At the highest serum calcium values, the calcium-phosphorus product increased and in individual rats, an increase in serum phosphorus was associated with a decrease in serum calcium. In summary, this study shows that (1) for rat 1-34 PTH, the normal replacement dose in the PTX rat with normal renal function on a normal diet is 0.022 microg/100 g/hour; (2) the relationship between PTH and both serum calcium and phosphorus is curvilinear, and an asymptote is reached for both; and (3) the calcium-phosphorus product is remarkably constant as the serum calcium increases from 7 to 13 mg/dl and only increased during marked hypercalcemia when serum phosphorus did not decrease further or even tended to increase.

Abnormal calcaemic response to PTH in the uraemic rat without secondary hyperparathyroidism.

BACKGROUND: Skeletal resistance to the calcaemic action of parathyroid hormone (PTH) is an important pathogenic factor in the development of secondary hyperparathyroidism. Since parathyroidectomy normalizes the calcaemic response to PTH in uraemic animals, the increase in PTH levels has been advanced as a cause of skeletal resistance to the calcaemic action of PTH. This study was designed to evaluate in uraemic rats the effect of normal PTH levels on the calcaemic response to PTH. METHODS: To maintain normal PTH levels, rats were parathyroidectomized (PTX) and rat 1-34 PTH was infused at a rate of 0.022 microg/100 g per hour via a subcutaneously implanted miniosmotic pump; this rate of infusion was considered to be the normal PTH replacement dose since it normalized serum calcium and phosphorus in PTX rats with normal renal function. Two separate studies were performed. In the first study, rats were maintained on a moderate-phosphorus (0.6%) diet and rats were divided into four groups: (I) normal; (II) uraemic; (III) PTX with normal PTH replacement; and (IV) uraemic with PTX and normal PTH replacement. In a second study, the groups were the same except that a high-phosphorus (1.2%) diet was given to increase the magnitude of hyperparathyroidism in rats with intact parathyroid glands; an additional group (V) identical to group IV except that rats received daily calcitriol was included. After 14 days, rats received a 48-h infusion of high-dose rat 1-34 PTH (0.11 microg/100 g per hour) to evaluate the calcaemic response to PTH. Results. The calcaemic response to PTH was similar in normal rats and PTX rats replacement on both a moderate and high-phosphorus diet. In uraemic rats, the calcaemic response to PTH was decreased and the maintenance of normal PTH levels by PTH replacement did not correct the decreased calcaemic response to PTH; moreover, calcitriol supplementation did not improve the calcaemic response to PTH. Finally, hypocalcaemia was observed in uraemic rats with PTH replacement and was more profound than in rats on a high-phosphorus diet. CONCLUSIONS: This study demonstrates that the maintenance of a normal PTH level in uraemic rats did not correct the impaired calcaemic response to PTH, suggesting that factors intrinsic to uraemia, independent of phosphorus, calcitriol, and PTH participate in the decreased calcaemic response to PTH in uraemia.

Relative effects of PTH and dietary phosphorus on calcitriol production in normal and azotemic rats.

In moderate renal failure, the serum calcitriol level is influenced by the stimulatory effect of high PTH and the inhibitory action of phosphorus retention. Our goal was to evaluate the relative effect that high PTH levels and increased dietary phosphorus had on calcitriol production in normal rats (N) and rats with moderate renal failure (Nx). Normal and Nx (3/4 nephrectomy) rats were divided into two groups: (1) rats with intact parathyroid glands (IPTG) and (2) parathyroidectomized rats in which PTH was replaced (PTHR) by the continuous infusion of rat 1-34 PTH, 0.022 microgram/hr/100 g body wt, using a miniosmotic Alzet pump. To test the effect of dietary phosphorus, rats received either a moderate (MPD, 0.6% P) or a high phosphorus (HPD, 1.2%) diet for 14 days. The experimental design included pair-fed N and Nx rats with either IPTG or PTHR. Serum calcitriol and PTH levels in N rats fed a MPD were 69 +/- 3 and 40 +/- 5 pg/ml, respectively. In Nx rats on a MPD, serum calcitriol levels decreased only if hyperparathyroidism was not allowed to occur (76 +/- 4 vs. 62 +/- 4 pg/ml in Nx-IPTG-MPD and Nx-PTHR-MPD groups respectively, P < 0.05). Even in N rats on a HPD, high PTH levels (67 +/- 8 pg/ml in the N-IPTG-HPD group) were required to maintain normal serum calcitriol levels (69 +/- 4 vs. 56 +/- 6 pg/ml in Nx-IPTG-HPD and Nx-PTHR-HPD groups, respectively; P < 0.05). In Nx rats on a HPD, the development of secondary hyperparathyroidism (286 +/- 19 pg/ml in the Nx-IPTG-HPD group) prevented a decrease in serum calcitriol levels (68 +/- 7 pg/ml). In contrast, serum calcitriol levels were low in the Nx-PTHR-HPD group (52 +/- 4 pg/ml, P < 0.05), which were deprived of the adaptative increase in endogenous PTH production. In conclusion, our results in rats indicate that in moderate renal failure, an elevated PTH level maintains calcitriol production and overcomes the inhibitory action of phosphorus retention.