Analytical solution of phosphate kinetics for hemodialysis.

Chronic kidney diseases imply an ongoing need to remove toxins, with hemodialysis as the preferred treatment modality. We derive analytical expressions for phosphate clearance during dialysis, the single pass (SP) model corresponding to a standard clinical hemodialysis and the multi pass (MP) model, where dialysate is recycled and therefore makes a smaller clinical setting possible such as a transportable dialysis suitcase. For both cases we show that the convective contribution to the dialysate is negligible for the phosphate kinetics and derive simpler expressions. The SP and MP models are calibrated to clinical data of ten patients showing consistency between the models and provide estimates of the kinetic parameters. Immediately after dialysis a rebound effect is observed. We derive a simple formula describing this effect which is valid both posterior to SP or MP dialysis. The analytical formulas provide explanations to observations of previous clinical studies.

Effect of far infrared therapy on arteriovenous fistula maturation, survival and stenosis in hemodialysis patients, a randomized, controlled clinical trial: the FAITH on fistula trial.

BACKGROUND: An arteriovenous fistula (AVF) is the preferred vascular access for hemodialysis treatment. After creation many of the AVFs will never mature or if functioning will need an intervention within 1 year due to an AVF stenosis. Studies investigating possible therapies that improves the AVF maturation and survival are scarce. Far infrared therapy (FIR) has shown promising results. In minor single centre and industry supported trials FIR has shown improved AVF maturation and survival. There is a need of a randomized multicentre controlled trial to examine the effect of FIR on the AVF maturation and survival and to explore the possible AVF protective mechanism induced by the FIR treatment. METHODS: This investigator initiated, randomized, controlled, open-labeled, multicenter clinical trial will examine the effect of FIR on AVF maturation in patients with a newly created AVF (incident) and AVF patency rate after 1 year of treatment in patients with an existing AVF (prevalent) compared to a control group. The intervention group will receive FIR to the skin above their AVF three times a week for 1 year. The control group will be observed without any treatment. The primary outcome for incident AVFs is the time from surgically creation of the AVF to successful cannulation. The primary outcome for the prevalent AVFs is the difference in number of AVFs without intervention and still functioning in the treatment and control group after 12 months. Furthermore, the acute changes in inflammatory and vasodilating factors during FIR will be explored. Arterial stiffness as a marker of long term AVF patency will also be examined. DISCUSSION: FIR is a promising new treatment modality that may potentially lead to improved AVF maturation and survival. This randomized controlled open-labelled trial will investigate the effect of FIR and its possible mechanisms. TRIAL REGISTRATION: Clinicaltrialsgov NCT04011072 (7th of July 2019).

Mortality due to bleeding, myocardial infarction and stroke in dialysis patients.

Essentials Mortality due to bleeding vs. arterial thrombosis in dialysis patients is unknown. We compared death causes of 201 918 dialysis patients with the general population. Dialysis was associated with increased mortality risks of bleeding and arterial thrombosis. Clinicians should be aware of the increased bleeding and thrombosis risks. SUMMARY: Background Dialysis has been associated with both bleeding and thrombotic events. However, there is limited information on bleeding as a cause of death versus arterial thrombosis as a cause of death. Objectives To investigate the occurrence of bleeding, myocardial infarction and stroke as causes of death in the dialysis population as compared with the general population. Methods We included 201 918 patients from 11 countries providing data to the ERA-EDTA Registry who started dialysis treatment between 1994 and 2011, and followed them for 3 years. Age-standardized and sex-standardized mortality rate ratios for bleeding, myocardial infarction and stroke as causes of death were calculated in dialysis patients as compared with the European general population. Associations between potential risk factors and these causes of death in dialysis patients were investigated by calculating hazard ratios (HRs) with 95% confidence intervals (CIs) by the use of Cox proportional-hazards regression. Results As compared with the general population, the age-standardized and sex-standardized mortality rate ratios in dialysis patients were 12.8 (95% CI 11.9-13.7) for bleeding as a cause of death (6.2 per 1000 person-years among dialysis patients versus 0.3 per 1000 person-years in the general population), 13.4 (95% CI 13.0-13.9) for myocardial infarction (22.5 versus 0.9 per 1000 person-years), and 12.4 (95% CI 11.9-12.9) for stroke (14.3 versus 0.7 per 1000 person-years). Conclusion Dialysis patients have highly increased risks of death caused by bleeding and arterial thrombosis as compared with the general population. Clinicians should be aware of the increased mortality risks caused by these conditions.

Senescence rates in patients with end-stage renal disease: a critical appraisal of the Gompertz model.

The most frequently used model to describe the exponential increase in mortality rate over age is the Gompertz equation. Logarithmically transformed, the equation conforms to a straight line, of which the slope has been interpreted as the rate of senescence. Earlier, we proposed the derivative function of the Gompertz equation as a superior descriptor of senescence rate. Here, we tested both measures of the rate of senescence in a population of patients with end-stage renal disease. It is clinical dogma that patients on dialysis experience accelerated senescence, whereas those with a functional kidney transplant have mortality rates comparable to the general population. Therefore, we calculated the age-specific mortality rates for European patients on dialysis (n=274 221; follow-up=594 767 person-years), for European patients with a functioning kidney transplant (n=61 286; follow-up=345 024 person-years), and for the general European population. We found higher mortality rates, but a smaller slope of logarithmic mortality curve for patients on dialysis compared with both patients with a functioning kidney transplant and the general population (P<0.001). A classical interpretation of the Gompertz model would imply that the rate of senescence in patients on dialysis is lower than in patients with a functioning transplant and lower than in the general population. In contrast, the derivative function of the Gompertz equation yielded the highest senescence rates for patients on dialysis, whereas the rate was similar in patients with a functioning transplant and the general population. We conclude that the rate of senescence is better described by the derivative function of the Gompertz equation.

Vitamin D, surface electromyography and physical function in uraemic patients.

BACKGROUND: Muscle function is impaired in uraemic patients and several causes have been proposed. Deficiency of 25-hydroxyvitamin D (25-OHD), which affects muscle function in non-uraemic patients, may very well also be associated with the myopathy found in these patients. The aim of this study was to investigate the association between 25-OHD and muscle function as well as physical function in chronic kidney disease (CKD) and peritoneal dialysis (PD) patients. METHODS: In this cross-sectional study, 21 adult patients with CKD stage 3-5 and 21 patients treated with PD were included. Standard biochemistry parameters were measured including 25-OHD, 1,25-dihydroxycholecalciferol (1,25-OHD) and parathyroid hormone analysis. Muscle function was determined by 30-second surface electromyography (sEMG) recordings of a right thigh muscle (vastus lateralis) and a second left finger muscle (second dorsal interosseous) under voluntary contractions. Physical function was determined using a 30-second Chair Stand Test and the Short Form 36 quality of life questionnaire. Clinical characteristics were collected from the patient records. RESULTS: Moderate vitamin 25-OHD deficiency (<40 nmol/l) was measured in 52% of patients with CKD and in 71% of the patients on PD. Severe deficiency (<15 nmol/l) was measured in 14% of patients on PD. There were no significant differences between the CKD and PD patients in terms of sEMG results. 25-OHD was not correlated to any results from the tests of sEMG or physical function. However, a higher sEMG frequency and signal root mean square (RMS) were positively associated with a higher Chair Stand Test score. Time to maximum sEMG frequency was negatively correlated to the Chair Stand Test score (p < 0.05), and positively correlated to the level of comorbidity (p < 0.05). sEMG signal peak-peak amplitude, frequency and RMS were positively correlated to the quality of life scales Physical Function, Role Physical, General Health, Vitality, Social Function, Mental Health, and Physical Component Scale (p < 0.001). CONCLUSIONS: 25-OHD deficiency was prevalent in uraemic patients in the present study. Muscle function as determined using sEMG and the Chair Stand Test was not associated with 25-OHD. The results may be biased by the limited variation in 25-OHD and masked by effects of several other variables in this very sick population.

Improved survival rate in patients with diabetes and end-stage renal disease in Denmark.

AIMS/HYPOTHESIS: We investigated the survival rate of Danish diabetic patients with end-stage renal disease (ESRD) between 1990 and 2005 and evaluated possible predictors of survival rate. MATERIALS AND METHODS: Data were obtained from the Danish National Register on Dialysis and Transplantation and from the Scandiatransplant database. Survival rates in different patient groups and association with age, sex, calendar time, waiting-list status and renal transplantation were evaluated using a multivariate Cox regression model. RESULTS: During the study period 8,421 patients (13% type 1 diabetic, 9% type 2 diabetic and 78% non-diabetic) started renal replacement therapy. The overall survival rate improved by 15% per five calendar years (hazard ratio [HR]=0.85, 95% CI: 0.81-0.88). The percentage of patients within each group who received renal transplantation was: type 1 diabetic: 26%, type 2 diabetic: 5%, non-diabetic: 24%. The survival rate of transplanted patients with diabetes mellitus (types 1 and 2) compared with non-diabetic patients at 1 year was: 95 vs 93%, at 5 years: 80 vs 85% and at 10 years: 52 vs 71%. Among diabetic patients survival rate was better in transplanted than in waiting-list patients (HR = 0.21, 95% CI 0.13-0.34), whereas the survival rate in waiting-list patients seemed to be superior to the survival rate among non-transplantation candidates (HR = 0.75, 95% CI 0.53-0.1.02, p = 0.07). CONCLUSIONS/INTERPRETATION: The survival rate of diabetic patients with ESRD has improved during the last 15 years. Although some selection bias may exist, significantly improved survival rate was observed among transplanted patients compared with dialysis patients on the waiting-list for transplantation. Renal transplantation should therefore be offered to diabetic patients with ESRD whenever possible.

Algorithm for optimal dialysis access timing.

BACKGROUND: Acute initiation of dialysis is associated with increased morbidity due to access and uremia complications. It is frequent despite early referral and regular out-patient control. We studied factors associated with end-stage renal disease (ESRD) progression in order to optimize the timing of dialysis access (DA). METHODS: In a retrospective longitudinal study (Study 1), the biochemical and clinical course of 255 dialysis and 64 predialysis patients was registered to determine factors associated with dialysis-free survival (DFS). On the basis of these results an algorithm was developed to predict timely DA, defined as >6 weeks and <26 weeks before dialysis initiation, with too late placement weighted twice as harmful as too early. The algorithm was validated in a prospective study (Study 2) of 150 dialysis and 28 predialysis patients. RESULTS: Acute dialysis was associated with increased 90-day hospitalization (17.9 vs. 9.0 days) and mortality (14% vs. 6%). P-creatinine and p-urea were poor indicators of DFS. At any level of p-creatinine, DFS was shorter with lower creatinine clearance and vice versa. Patients with systemic renal disease had a significantly shorter DFS than primary renal disease, due to faster GFR loss and earlier dialysis initiation. Short DFS was seen with hypoalbuminemia and cachexia; these patients were recommended early DA. The following algorithm was used to time DA (units: 1iM and ml/min/1.73 m2): P-Creatinine - 50 x GFR + (100 if Systemic Renal Disease) >200. Use of the algorithm was associated with earlier dialysis placement and a fall in acute dialysis requirements from 50% to 23%. The incidence of too early DA was unchanged (7% vs. 9%), and was due to algorithm non-application. The algorithm failed to predict imminent dialysis in 10% of cases, primarily due to acute exacerbation of stable uremia. Dialysis initiation was advanced by approximately one month. CONCLUSIONS: A predialysis program based on early dialysis planning and GFR-based DA timing may reduce the requirement for acute dialysis initiation and patient morbidity and mortality, at the cost of slightly earlier dialysis initiation.

Stabilized incidence of diabetic patients referred for renal replacement therapy in Denmark.

Despite an improvement in diabetes care during the last 20 years, the number of diabetic patients starting renal replacement therapy (RRT) has continued to increase in the Western world. The aim was to study the incidence of patients starting RRT in Denmark from 1990 to 2004. Data were obtained from The Danish National Registry; Report on Dialysis and Transplantation, where all patients actively treated for end-stage renal disease have been registered since 1990. The incidence of end-stage renal disease increased until 2001. Thereafter the incidence stabilized on 130 per million people (pmp). The number of diabetic patients starting RRT increased steadily from: 52 (number of patients) in 1990, 113 in 1995, 150 in 2000, 168 in 2001, and 183 in 2002. However, during the years 2003 and 2004 this number was significantly reduced by 15% to 156 and 155, respectively. This was mainly due to a 22% reduction in the number of non-insulin- treated (type II) diabetic patients (number of patients): 98, 82, and 76 in 2002, 2003, and 2004, respectively. The mean age in the background population, the mean age in diabetic patients starting RRT and the incidence of type I and type II diabetes increased during the study period. The encouraging stabilization in the incidence of diabetic patients referred for RRT observed in Denmark could be the result of implementation of a multifactorial and more intensive renoprotective intervention in patients with diabetes and chronic progressive renal disease.

A high peritoneal large pore fluid flux causes hypoalbuminaemia and is a risk factor for death in peritoneal dialysis patients.

BACKGROUND: Hypoalbuminaemia is common in peritoneal dialysis (PD) patients and has an associated high mortality. An excess morbidity and mortality has previously been found in patients with high peritoneal transport. A high peritoneal large pore fluid flux (Jv(L)) results in increased peritoneal loss of protein that possibly contributes to patient morbidity. Alternatively, hypoalbuminaemia and high transport status could be just a marker of capillary pathology associated with atherosclerotic comorbidity. METHODS: Peritoneal dialysis capacity computer modelling of peritoneal transport, based on Rippe's three-pore model, was performed to measure Jv(L) in 155 incident PD patients 2-4 weeks after PD initiation. Patient clinical and biochemical status was determined -6, -3, -1, 1 and 6 months after PD initiation, and every 6 months thereafter. Jv(L) was redetermined in prevalent patients 2 and 4 years after PD initiation. RESULTS: Jv(L) was 0.106+/-0.056 ml/min/1.73 m(2) (median 0.094, interquartile range 0.068-0.128). It was correlated to age*** (*P<0.05; **P<0.01; ***P<0.001) (20-30 years 0.079+/-0.04; 70 years 0.121+/-0.071), but not to gender. No correlation to diabetic or preexisting renal replacement therapy was seen, but patients with atherosclerosis had higher Jv(L) (0.123+/-0.06 vs 0.100+/-0.056*) as had patients with other systemic disease (0.121+/-0.68 vs 0.100+/-0.051*). Jv(L) was positively correlated to area parameter (r = 0.41***), and negatively correlated to plasma albumin (-0.36***). Patients were divided into three equal groups: group 1, Jv(L) <0.075 ml/min/1.73 m(2); group 2, 0.075-0.11; group 3: >0.11. There was no difference between the groups in p-albumin prior to PD. Immediately after PD start, differences between the three groups appeared (1 month p-albumin: (micromol/l) group 1, 548+/-83; group 2, 533+/-86; group 3, 497+/-78**), and persisted for up to 6 years. No significant change in Jv(L) was seen at 2 and 4 years. Patients with significant albuminuria also had hypoalbuminaemia (<1 g/day: 546+/-81 mumol/l; >2 g/day: 503+/-54 micromol/l). Intermittent PD ameliorated the effect of Jv(L) on albumin losses and clearance. Mortality was increased significantly with raised Jv(L), independently of age (2 year mortality: group 1, 10%, group 3, 32%*). There was no overall effect on technique survival, but hypoalbuminaemic group 3 patients had a higher failure rate. CONCLUSION: Jv(L) is related to hypoalbuminaemia and mortality after PD initiation. A high Jv(L) seems to be a marker of preexisting vascular pathology, and to cause hypoalbuminaemia after PD initiation. It is suggested that peritoneal albumin loss can have an identical pathogenic effect as urinary albumin loss, by causing an iatrogenic "nephrotic" syndrome.

The relative prognosis of nodular and diffuse diabetic nephropathy.

MATERIAL AND METHODS: One hundred and forty-four diabetic patients with biopsy-proven diffuse diabetic glomerulosclerosis (DIF), 134 patients with nodular diabetic nephropathy (NOD) and 152 diabetic patients with nondiabetic-related morphology (104 chronic nephropathy, 48 primary GN) were followed for up to 12 years to determine the clinical prognosis. RESULTS: Comparing the NOD patients with the DIF patients, there were more females (41% vs 26%, p < 0.05) and they were more often uremic at biopsy (24% vs 12%, p < 0.01), but the age was similar (53.3 years vs 50.1 years, NS). There was no difference in diabetes type I and II incidence. Compared with the general population, the odds ratio (OR) for death was 7.2 (confidence interval 5.5-9.5) for DIF and 10.8 (8.5-13.7) for NOD. The OR for combined renal or patient death was: DIF 15.2 (11.7-19.7); NOD 24.6 (19.4-31.0). After correction for age, sex, and pre-existing uremia, NOD had a 1.70 (p < 0.01) times increased risk of death compared with DIF, and a 2.42 (p < 0.01) times increased risk of renal failure. The life expectancy for NOD was 4.0 years, and average time to dialysis was 2.1 years. NOD prognosis was similar to other chronic nephropathy. The incidence of all atherosclerotic complications except AMI was twice as high in NOD than DIF. Diabetes type had no influence on prognosis. The estimated incidence of diabetic nephropathy was 56/mio/year. CONCLUSION: Nodular diabetic nephropathy has a poorer prognosis than diffuse due to a higher rate of atherosclerotic and uremic complications.

Bone loss after renal transplantation: role of hyperparathyroidism, acidosis, cyclosporine and systemic disease.

UNLABELLED: In order to determine risk factors for bone loss after renal transplantation, dual energy X-ray absorptiometry was performed in 125 renal transplant patients. The bone mineral density (BMD) was expressed as a percentage of the normal population (BMD%) and Z-score (SD from normal). The whole body, lumbar spine and femoral neck BMD% (Z-score) values were 93.9 +/- 8.9 (-0.90 SD), 91.6 +/- 14.9 (-0.98 SD) and 87 +/- 15.3 (-1.0 SD)%, respectively. Low BMD% was associated with low creatinine clearance ( < 40 mL/min: 91.6 +/- 7.9, > 40 mL/min: 95.6 +/- 8.0, p < 0.01), repeated graft loss (0: 94.4 +/- 9.1, > 1: 87.4 +/- 9.3, p < 0.05), long dialysis duration ( < 1 yr: 95.2 +/- 7.9, > 5: 90.1 +/- 10.6, p < 0.05), acidosis (bicarbonate < 21 mmol/L: 89.6 +/- 8.0, > 27: 96.7 +/- 7.2, p < 0.01), secondary and tertiary hyperparathyroidism ( < 50 ng/L: 95.9 +/- 7.1, > 200: 87.7 +/- 5.0, p < 0.01), raised alkaline phosphatase ( < 200 units/L: 95.7 +/- 7.2, > 300: 85.6 +/- 13.2, p < 0.001), osteocalcin ( < 50 microg/L: 95.2 +/- 6.7, > 100: 89.3 +/- 7.6, p < 0.01) and urinary deoxypyridinoline (< 5 nM/mM creatinine: femoral neck 89.6 +/- 10.7, > 10: 82.1 +/- 20.1, p < 0.05), low 25-OH-vitamin D ( < 10 microg/L: 91.3 +/- 9.8, > 20: 96.9 +/- 7.4, p < 0.001) and high cyclosporine concentration (0 ng/L: 98.3 +/- 7.0, > 150: 92.1 +/- 9.3, p < 0.05). Patients with clinical atherosclerosis (91.7 +/- 8.6 vs. 95.4 +/- 8.8, p < 0.01), hypoalbuminemia ( < 550 micromol/L: 87.6 +/- 13.2, > 550: 94.2 +/- 7.8, p < 0.01), renovascular disease (89.7 +/- 5.7 vs. 95.0 +/- 5.7, p < 0.05) and diabetic nephropathy (femoral neck 76.6 +/- 8.8 vs. 89.3 +/- 15.1, p < 0.01) had lower bone masses. High bone mass was associated with previous dialysis alphacalcidol therapy (0: 92.2 +/- 7.5, > 3 microg/wk: 97.3 +/- 6.9, p < 0.05). No relationships with transplantation duration, 1,25-OH-vitamin D, aluminium, calcium or steroid dose were found. No involutional changes in tertiary hyperparathyroidism could be discerned. CONCLUSION: The major threats to bone mass after renal transplantation appear to be ongoing hyperparathyroid bone disease, low renal function, acidosis, systemic disease and hypo-vitaminosis D.

Uses and limitations of renal scintigraphy in renal transplantation monitoring.

The value of thrice weekly technetium-99m mercaptoacetyltriglycine renography after renal transplantation was investigated in 213 consecutive transplants. A grading system was used: 0 = normal renogram; 1 = normal uptake, reduced excretion; 2 = normal uptake, flat excretion curve; 3 = rising curve; 4 = reduced rate of uptake, rising curve and reduced absolute uptake; 5 = minimal uptake. The initial renogram grade (RG) was primarily a marker of ischaemic damage, being poorer with cadaver donation, long cold ischaemia (>24 h), and high donor and recipient age. High primary RG predicted primary graft non-function, long time to graft function, low discharge Cr EDTA clearance and low 1- and 5-year graft survival. Discharge RG predicted late (>6 months) graft loss. RG was highly correlated (P<0.001) with creatinine and creatinine clearance, and changes in RG were correlated with changes in renal function. A change in RG of 0.5 was non-specific, while a change of 1 or more predicted clinical complications in 95% of cases. The negative predictive value was low (58%). RG change antedated clinical diagnosis in only 38% of cases, and in only 14% of acute rejections did an RG change of 1 or more antedate a rising creatinine. RG did not contribute to the differential diagnosis between acute rejection, acute tubulointerstitial nephropathy and cyclosporine toxicity. In conclusion, an initial renography after transplantation is valuable as it measures ischaemic damage and predicts duration of graft non-function and both short and long-term graft survival. A review of the literature suggests that the indication for serial scintigraphic monitoring for functioning grafts is less certain: the diagnostic specificity is insufficient for it to be the definitive investigation for common diagnostic problems and it does not give sufficient advance warning of impending problems.

Pathogenic effects of a high peritoneal transport rate.

Recent studies have shown that patients with high peritoneal transport characteristics have substantially increased morbidity and mortality. This finding is counter-intuitive, since HTs will a priori achieve higher clearances. There are many possible causes: increased protein losses with consequent hypoalbuminemia; poor ultrafiltration capacity causing fluid retention, ventricular hypertrophy and hypertension; increased glucose absorption leading to anorexia, hyperinsulinism, and local AGE formation; and the development of an atherogenic lipid profile. While common pathogenic causes of high peritoneal transport and atherosclerosis have been hypothesized, it is more likely that CAPD as currently practiced is unsuitable for HTs, who should be switched to HD or NIPD. Renal and peritoneal clearances have different clinical effects and should be assessed separately. Current measures of dialysis adequacy, such as total Kt/V, do not therefore describe the patient's clinical situation accurately and are insufficient.

The epidemiology and prognosis of glomerulonephritis in Denmark 1985-1997.

BACKGROUND: The existence of a national renal biopsy register and a national terminal uraemia status register in Denmark provides an opportunity to study the prognosis of glomerulonephritis (GN), and factors influencing prognosis. METHODS: Multivariate analysis of 2380 renal biopsies with GN performed between 1985 and 1997 was done to determine the influence of clinical and histological factors on prognosis. RESULTS: The incidence of GN (39/mo/year) and individual diagnoses did not change during the period. After 10 years, 32%, were dead, 13% terminally uraemic, 5%, uraemic and 50% well. Older age increased mortality, but not the incidence of renal failure after the first year. Male sex increased both mortality and incidence of renal failure (34 vs 24% at 10 years, P < 0.001). The diagnoses could be divided into three prognostic groups compared with the general population: a good prognostic group (minimal change GN and membranous GN ), with a relative mortality of three and a combined renal and patient mortality of four; a poor prognostic group [crescentic GN, HUS/TTP, chronic GN] with relative mortalities of 8-19 and 13-33, respectively; and the remainder with mortalities of 4-7 and 6-12. The presence of multiple glomerular pathology, chronic GN, nephrosclerosis and chronic interstitial nephropathy worsened the prognosis, while the presence of immune deposits only worsened the prognosis of focal segmental glomerulopathy. Mortality was related to uraemia and co-morbidity at biopsy, and to the incidence of renal failure. Renal failure was correlated to uraemia and hypertension at biopsy but not to nephrotic syndrome or atherosclerosis. All vascular complications were increased and were positively related to hypertension and negatively correlated to the incidence of uraemia. Crescentric glomerulonephritis combined with anti-GBM disease had a worse prognosis than Wegener's granulomatosis, with microscopic polyangiitis and pauci-immune disease occupying an intermediate position. The prognosis of mesangioproliferative GN was unaffected by the presence of IgA nephropathy and systemic lupus erythematosus.

The cellular clearance theory does not explain the post-dialytic small molecule rebound.

AIM: (a) To determine the normalized cellular clearance (Kcn) of urea, creatinine and phosphate in patients undergoing maintenance hemodialysis; (b) To identify the factors, particularly circulatory, which determine Kcn; (c) To evaluate whether intra-dialytic blood sampling can predict the size of the post-dialytic solute concentration rebound. METHODS: Kinetic modelling of urea, creatinine and phosphate, using a two-pool variable volume computer simulation, was performed on two occasions on 34 patients undergoing maintenance dialysis. The cellular clearance was determined (a) from the size of the rebound 50 min after the end of dialysis; (b) from a mid-dialytic blood sample. Conventional two-dimensional M-mode echocardiography and Doppler peripheral blood pressure measurement were performed. RESULTS: The model produced accurate measurements of rebound Kc for urea in 93% of measurements, creatinine in 49% and phosphate in 13%. The corresponding figures for mid-dialysis Kcn were 76%, 39% and 0%. The rebound Kcn was, for urea, 8.31 +/- 4.31 ml/kg/min, and for creatinine 4.07 +/- 2.98. The mid-dialysis Kcn was, for urea, 8.57 +/- 4.25 ml/kg/min, and for creatinine 5.06 +/- 3.36. High post-dialytic rebounds (and low Kcn values) were associated with erythropoietin use (p < 0.05) and occurrence of end-dialytic hypotension (p < 0.02). Patients treated with calcium antagonists had a significantly (p < 0.001) higher Kcn. There was no correlation between mid-dialysis and rebound Kcn. Circulatory indices had no influence on Kcn. CONCLUSIONS: The two-pool cellular clearance model is compatible with urea kinetics, but not creatinine or phosphate. It is therefore unlikely that it is the correct model for small molecule kinetics. The post-dialytic solute rebound may be partly an iatrogenic phenomenon and can be reduced by preventing post-dialytic hypotension and by calcium antagonist treatment, both of which improve regional blood flow. The size of the rebound cannot be predicted by intra-dialytic blood sampling.

Parathyroid hormone during maintenance dialysis: influence of low calcium dialysate, plasma albumin and age.

UNLABELLED: Intact PTH measurements between 1989-96 in a 116-patient (63 HD, 53 PD) dialysis unit were reviewed to evaluate the determinants of PTH. Prophylactic treatment included calcium carbonate and maximal alphacalcidol therapy. A forward stepwise multiple regression analysis showed that duration of dialysis, phosphate, albumin and chronic glomerulonephritis were independently positively correlated with PTH, and that ionized calcium, parathyroidectomy, age, diabetic nephropathy and systemic disease were independently negatively correlated. During the first five years of dialysis PTH rose from 124 ng/L (SD range 33-462) to 160 (63-402)* in HD patients but fell from 119 ng/L (33-423) to 88 (31-251)** in PD patients despite the less intensive treatment. PTH fell with increasing age (40-50 years 173 ng/L (52-575); > 60 years 100 (31-316)**) and hypoalbuminemia (< 400 micromol/L 68 ng/L (22-209); > 550 pmol/1138 (41-457)**). PD patients were generally older and increasingly malnourished; after correcting for these factors, no influence of dialysis modality on PTH could be seen. Low-calcium dialysate (1.25 mmol/L) was introduced for both dialysis groups in 1994. Consequent to this, aluminium consumption was virtually eliminated and consumption of alphacalcidol increased. PTH fell from 161 to 128 ng/L in HD patients but rose from 119 to 135 ng/L in PD patients. The incidence of parathyroidectomy fell from 4.3%/year to 1.5%/year*. CONCLUSION: Malnourishment and increasing age reduce PTH secretion and are important determinants of hyperparathyroidism during maintenance dialysis. Adynamic bone disease is common in PD patients and associated with low PTH levels, and may be a consequence of malnourishment and involutional changes. The introduction of low-calcium dialysate reduced the incidence of parathyroidectomy. Control of hyperparathyroidism improved in HD but not PD patients.

The effect of acute rejection on long-term renal graft survival is mainly related to initial renal damage.

It has been suggested that poor long-term prognosis of acute rejection is due to hyperfiltration-mediated injury secondary to the initial renal damage, rather than to ongoing immunological mechanisms. A total of 953 renal transplant recipients was reviewed to examine the effect of acute rejection episodes on graft function and survival; 40% had no rejections, 45% one, 12% two and 3% three. Rejection episodes adversely affected short- and long-term prognosis (5-year survival for no rejections, 62%; one, 34%; two, 26%; three, 19%, P < 0.001) and creatinine clearance at one year (cl 1) (none, 56.7 ml/ min; one, 51.1; two, 52.9; three, 35.2, P < 0.01). This was mainly due to increased graft loss, but patient survival was also reduced (5-year survival for no rejections, 77%; one, 76%; two, 63%; three, 53%, P < 0.05). There was no overall effect of rejection number, independently of cl 1. However, subgroup analysis showed a detrimental effect of rejection number on grafts with high residual function, i.e. cl 1 > 60 ml/min (5-year graft survival none and one, 87%; two and three, 71%, P < 0.01). Late initial rejection episodes adversely affected prognosis (5-year survival 1-7 days, 34%; 8-60, 31%; 60-300, 21%, P < 0.05) and residual graft function (cl 1 1-7 days, 56.2 ml/min; 8-60, 48.7; 60-300, 44.6, P < 0.01). In conclusion, the poor long-term prognostic effect of rejection episodes is mainly, but not entirely, related to initial graft destruction. Late (> 2 months after transplantation) initial rejection is an important independent risk factor for graft loss.