Loss via peritoneal fluid as a factor for low 25(OH)D3 level in peritoneal dialysis patients

A feasibility study of avoiding positive calcium balance and parathyroid hormone increase in patients on peritoneal dialysis

Background

The effect of the dialysate calcium concentration (D[Ca]) on mineral and bone metabolism in patients on peritoneal dialysis (PD) is overlooked. D[Ca] of 1.75 mmol/L is still prescribed to many patients on PD around the world. Previous studies on the effects of reducing D[Ca] have been carried out before the incorporation of calcimimetics in clinical practice. We hypothesized that a reduction in D[Ca] is safe and without the risk of a rise in serum parathyroid hormone (PTH).

Methods

In this non-randomized clinical trial, the D[Ca] was reduced from 1.75 mmol/L to 1.25 mmol/L for one year in prevalent patients on PD. Demographic, clinical, and CKD-MBD-related biomarkers were evaluated at baseline, 3, 6, and 12 months of follow-up.

Results

20 patients completed 1-year follow-up (56 ± 16 years, 50 % male, 25 % diabetic, 55 % with baseline parathyroid hormone – PTH >300 pg/mL). Over time, there was no significant change in calcium, phosphate, total alkaline phosphatase, 25(OH)-vitamin D or PTH, although adjustments in calcitriol and sevelamer prescription were required. After 1 year, absolute and percentual change in PTH levels were 36 (−58, 139) pg/mL, and 20 % (−28, 45) respectively. The proportion of patients with PTH > 300 pg/mL did not change during the follow-up (p = 0.173).

Conclusion

Knowing the risk of a positive calcium balance in patients on PD, reducing the D[Ca] concentration is a safe and valuable option, although medication adjustments are needed to detain PTH rising.

Vitamin D status and mortality risk among patients on dialysis: a systematic review and meta-analysis of observational studies

Background

Vitamin D deficiency is highly prevalent in patients on dialysis. Although vitamin D deficiency is closely associated with cardiovascular disease (CVD) and high mortality in the general population, the relationship between serum 25-hydroxyvitamin D [25(OH)D] and all-cause and cardiovascular mortality in dialysis patients is uncertain. We aim to explore the relationship between serum 25(OH)D levels and all-cause and cardiovascular mortality in dialysis patients.

Methods

This is a systematic review and meta-analysis of clinical studies among patients receiving maintenance dialysis. We did a systematic literature search in PubMed and Embase to identify studies reporting the relationship between serum 25(OH)D levels and all-cause and cardiovascular mortality in patients on dialysis. The search was last updated on 10 February 2017.

Results

The study included 18 moderate to high-quality cohort studies with an overall sample of 14 154 patients on dialysis. The relative risk of all-cause mortality per 10 ng/mL increase in serum 25(OH)D level was 0.78 [95% confidence interval (CI) 0.71-0.86], although there was marked heterogeneity (I2=96%, P < 0.01) that was partly explained by differences in CVD prevalence, baseline parathyroid hormone level and dialysis duration among included studies. The relative risk of cardiovascular mortality per 10 ng/mL increase in serum 25(OH)D level was 0.71 (95% CI 0.63-0.79), with substantial heterogeneity (I2=74%, P=0.004) that was largely explained by differences in study type and serum 25(OH)D measurement method.

Conclusions

In the present study, increased serum 25(OH)D level was significantly associated with lower all-cause mortality and lower cardiovascular mortality in dialysis patients.

Clinical management of patients on peritoneal dialysis in Italy: results from the ATENA study

BACKGROUND

In Italy, few studies have examined the clinical management of peritoneal dialysis (PD) patients, resulting in a lack of information and awareness.

METHODS

A total of 378 PD patients (64.7 ± 14.3 years, 58.9% males) were enrolled across 15 centres in a 12-month retrospective and 6-month prospective study. The primary objective was to evaluate the achievement of Kidney Disease Outcomes Quality Initiative and Kidney Disease Improving Global Outcomes guidelines on recommended target values for anaemia, high blood pressure and mineral metabolism. Comorbidities, hospitalizations, treatment and quality of life were also assessed.

RESULTS

Frequent comorbidities included hypertension (87.8%) and cardiovascular disease (39.7%). Peritonitis was the leading cause of hospitalization [12 admissions per 100 person-years (95% confidence interval 9.3-15.2)]. At 6 months, anaemia corrected by erythropoiesis-stimulating agents was observed in 30% of patients and 73% received erythropoiesis-stimulating agents. Systolic and diastolic blood pressures were recorded in 50% and 20% of patients, respectively. Sixty-four percent of echocardiograms revealed left ventricular hypertrophy and 30% of patients had vitamin D <10 ng/mL. Medication to treat intact parathyroid hormone (PTH) included calcitriol (36.3%), paricalcitol (29.2%), cholecalciferol (23.6%) and cinacalcet (21.5%). In a subgroup of patients matched for baseline PTH treated for 1 year, a significant reduction in PTH with paricalcitol (-41%; P < 0.001) but not cinacalcet (+2%; P = 0.63) was observed. Comparison of quality of life domains revealed significant differences for symptoms (P = 0.049), cognitive function (P = 0.019) and social support (P = 0.04) (baseline versus 6 months).

CONCLUSIONS

Hypertension and cardiovascular diseases were frequent comorbidities and peritonitis was the leading cause of hospitalization. Secondary hyperparathyroidism and anaemia were common, thus necessitating frequent monitoring of PTH, calcium, phosphorus and haemoglobin.

[Vitamin D deficiency and morbimortality in critically ill paediatric patients]

OBJECTIVES

To determine the prevalence and risks factors of vitamin D deficiency, as well as its relationship with morbidity and mortality in a PICU.

MATERIAL AND METHODS

An observational prospective study in a tertiary children's University Hospital PICU conducted in two phases: i: cohorts study, and ii: prevalence study. The study included 340 critically ill children with ages comprising 6 months to 16 years old.

EXCLUSION CRITERIA

Chronic kidney disease, known parathyroid disorders, and vitamin D supplementation. Total 25-hydroxyvitamin D [25(OH)D] was measured in the first 48hours of admission to a PICU. Parathormone, calcium, phosphate, blood gases, blood count, C-reactive protein, and procalcitonin were also analysed. A record was also made of demographic features, characteristics of the episode, and complications during the PICU stay.

RESULTS

The overall prevalence rate of vitamin D deficiency was 43.8%, with a mean of 22.28 (95% CI 21.15-23.41) ng/ml. Patients with vitamin D deficiency were older (61 vs 47 months, P=.039), had parents with a higher level of academic studies (36.5% vs 20%, P=.016), were admitted more often in winter and spring, had a higher PRISM-III (6.8 vs 5.1, P=.037), a longer PICU stay (3 vs 2 days, P=.001), and higher morbidity (61.1% vs 30.4%, P<001) than the patients with sufficient levels of 25(OH)D. Patients who died had lower levels of 25(OH)D (14±8.81ng/ml versus 22.53±10.53ng/ml, P=.012). Adjusted OR for morbidity was 5.44 (95%CI; 2.5-11.6).

CONCLUSIONS

Vitamin D deficiency is frequent in critically ill children, and it is related to both morbidity and mortality, although it remains unclear whether it is a causal relationship or it is simply a marker of severity in different clinical situations.

Relative importance of the determinants of serum levels of 25-hydroxy vitamin D in patients with chronic kidney disease

INTRODUCTION

The cause of vitamin D deficiency in chronic kidney disease (CKD) is probably multi-factorial; however, the relative importance of each potential determinant is uncertain.

AIMS

To determine factors associated with serum levels of 25-hydroxy vitamin D (25OHD) and their relative importance in a cohort of pre-dialysis CKD patients.

MATERIAL AND METHODS

Incident patients admitted to a CKD outpatient clinic were included. Those who were receiving vitamin D supplements or anticonvulsants were excluded. In addition to demographic and clinical data, information about outdoor physical activity, season of blood collection, prescription of statins, anti-angiotensin drugs and xanthine-oxidase inhibitors were included as potential determinants. Johnson's relative weights analysis was used to estimate the relative importance of each potential determinant and the results were expressed as percentage contribution to multiple R.

RESULTS

The study group consisted of 397 patients, 30 of whom were excluded. The mean serum level of 25OHD was 13.7±7.4ng/ml, and 81% of patients had serum levels lower than 20ng/ml. By multiple linear regression and relative weights analyses, the best determinants of low serum 25OHD levels and their relative importance were: higher proteinuria (28.5%), old age (21.4%), low physical activity (19.4%), female gender (19.3%) and low serum bicarbonate levels (11.4%).

CONCLUSIONS

Proteinuria and age are the determinants with the highest relative importance for predicting 25OHD levels in CKD patients.

Vitamin D deficiency in critically ill children with sepsis

BACKGROUND

Data on the prevalence of vitamin D deficiency (VDD) in critically ill children with sepsis and its association with illness severity and outcome are limited.

AIM

To investigate the prevalence of VDD in critically ill children with sepsis.

METHODS

One hundred and twenty-four critically ill children with sepsis aged 1-12 years were prospectively enrolled in a paediatric intensive care unit (PICU) in North India over a 1-year period. Demographic data, clinical signs and risk factors for VDD, Paediatric Index of Mortality III (PRISM III) score, and sequential organ failure assessment (SOFA) score were recorded. Plasma 25-hydroxy vitamin D [25(OH)D] levels were measured by ELISA within 24 hours of admission. The occurrence of septic shock, multiple organ dysfunction syndrome (MODS) and healthcare-associated infection (HCAI), need for mechanical ventilation and catecholamines, length of PICU stay and mortality were also recorded. Cases were compared with 338 apparently healthy children for baseline variables and vitamin D status.

RESULTS

Prevalence of VDD [25(OH)D level < 50 nmol/L] was higher among critically ill children with sepsis compared to healthy controls (50.8% vs 40.2%, P = 0.04). VDD was not associated with any significant difference in baseline demographic variables or risk factors for VDD. Although there was a trend toward increased PRISM III score, septic shock, MODS, HCAI, need for mechanical ventilation and catecholamines, length of PICU stay, and mortality, the difference was not statistically significant.

CONCLUSION

A high prevalence of VDD in critically ill children with sepsis was found but it was not associated with greater severity of illness or other clinical outcomes.

Peritoneal dialysis per se is a risk factor for sclerostin-associated adynamic bone disease

Chronic kidney disease--mineral bone disorder (CKD-MBD) is a complex syndrome influenced by various factors, such as age, CKD etiology, uremic toxins, and dialysis modality. Although extensively studied in hemodialysis (HD) patients, only a few studies exist for peritoneal dialysis (PD) patients. Since most of these older studies contain no bone biopsy data, we studied the pattern of renal osteodystrophy in 41 prevalent PD patients. The most common presentation was adynamic bone disease (49%). There was a significant inverse association between serum sclerostin (a Wnt/β-catenin pathway inhibitor that decreases osteoblast action and bone formation) and the bone formation rate. Bone alkaline phosphatase had the best sensitivity and specificity to detect both high- and low-turnover diseases. The comparison between nondiabetic PD and HD patients, matched by age, gender, parathyroid hormone level, and length of dialysis, revealed low 25-hydroxyvitamin D levels, worse bone mineralization, and low bone turnover in the nondiabetic PD group. Thus, adynamic bone disease was the most frequent type of renal osteodystrophy in PD patients. Sclerostin seems to participate in the pathophysiology of adynamic bone disease and bone alkaline phosphatase was the best serum marker of bone turnover in these patients.

Effects of vitamin D on parathyroid hormone and clinical outcomes in peritoneal dialysis: a narrative review

Vitamin D deficiency is very prevalent in dialysis and peritoneal dialysis (PD) patients show lower levels of cholecalciferol (25(OH)D3) than hemodialysis patients. We conducted a systematic narrative review to assess the effects of vitamin D therapy on control of secondary hyperparathyroidism and clinical outcomes induced by vitamin D pleiotropic effects. Medline database was searched for cohort and intervention studies reporting data on vitamin D (all sterols including synthetic analogs) and peritoneal dialysis without language restriction. Two authors independently extracted data. Twenty-nine observational and eleven interventional studies were identified for inclusion (1,036 subjects). PTH levels decreased in twenty-nine studies, increased in one study and remained stable in ten studies. Thirty-three studies analyzed the oral route for vitamin D administration, ten the intraperitoneal, one the subcutaneous and one the intravenous. A significant decrease of peritonitis risk was observed in two studies. Proteinuria decreased in four studies and remained stable in one study. Peritoneal protein loss decreased in one study and was stable in two studies. Studies on the therapeutic effects of vitamin D in PD are limited and describe small population samples. Moreover, vitamin D compounds do not consistently reduce PTH levels. The administration of active vitamin D in PD may have interesting pleiotropic effects such as decreasing proteinuria and peritoneal protein loss. According to these effects, vitamin D could help to preserve residual renal function and ensure efficient peritoneal membrane dialysance.

Serum 25-hydroxy vitamin D concentrations are more deficient/insufficient in peritoneal dialysis than haemodialysis patients in a sunny climate

BACKGROUND

Research has identified associations between serum 25(OH)D and a range of clinical outcomes in chronic kidney disease and wider populations. The present study aimed to investigate vitamin D deficiency/insufficiency in dialysis patients and the relationship with vitamin D intake and sun exposure.

METHODS

A cross-sectional study was used. Participants included 30 peritoneal dialysis (PD) (43.3% male; 56.87 ± 16.16 years) and 26 haemodialysis (HD) (80.8% male; 63.58 ± 15.09 years) patients attending a department of renal medicine. Explanatory variables were usual vitamin D intake from diet/supplements (IU day(-1) ) and sun exposure (min day(-1) ). Vitamin D intake, sun exposure and ethnic background were assessed by questionnaire. Weight, malnutrition status and routine biochemistry were also assessed. Data were collected during usual department visits. The main outcome measure was serum 25(OH)D (nm).

RESULTS

Prevalence of inadequate/insufficient vitamin D intake differed between dialysis modality, with 31% and 43% found to be insufficient (<50 nm) and 4% and 33% found to be deficient (<25 nm) in HD and PD patients, respectively (P < 0.001). In HD patients, there was a correlation between diet and supplemental vitamin D intake and 25(OH)D (ρ = 0.84, P < 0.001) and average sun exposure and 25(OH)D (ρ = 0.50, P < 0.02). There were no associations in PD patients. The results remained significant for vitamin D intake after multiple regression, adjusting for age, gender and sun exposure.

CONCLUSIONS

The results highlight a strong association between vitamin D intake and 25(OH)D in HD but not PD patients, with implications for replacement recommendations. The findings indicate that, even in a sunny climate, many dialysis patients are vitamin D deficient, highlighting the need for exploration of determinants and consequences.

Renal anaemia and EPO hyporesponsiveness associated with vitamin D deficiency: the potential role of inflammation

Resistance to erythropoiesis-stimulating agents (ESAs) has been observed in a considerable proportion of patients with chronic kidney disease (CKD) and it is reportedly associated with adverse outcomes, such as increased cardiovascular morbidity, faster progression to end-stage renal disease (ESRD) and all-cause mortality. The major causes of ESA resistance include chronic inflammation producing suppressive cytokines of early erythroid progenitor proliferation. In addition, pro-inflammatory cytokines stimulate hepcidin synthesis thus reducing iron availability for late erythropoiesis. Recent studies showing an association in deficiencies of the vitamin D axis with low haemoglobin (Hb) levels and ESA resistance suggest a new pathophysiological co-factor of renal anaemia. The administration of either native or active vitamin D has been associated with an improvement of anaemia and reduction in ESA requirements. Notably, these effects are not related to parathyroid hormone (PTH) values and seem to be independent on PTH suppression. Another possible explanation may be that calcitriol directly stimulates erythroid progenitors; however, this proliferative effect by extra-renal activation of 1α-hydroxylase enzyme is only a hypothesis. The majority of studies concerning vitamin D deficiency or supplementation, and degree of renal anaemia, point out the prevalent role of inflammation in the mechanism underlying these associations. Immune cells express the vitamin D receptor (VDR) which in turn is involved in the modulation of innate and adaptive immunity. VDR activation inhibits the expression of inflammatory cytokines in stromal and accessory cells and up-regulates the lymphocytic release of interleukin-10 (IL-10) exerting both anti-inflammatory activity and proliferative effects on erythroid progenitors. In CKD patients, vitamin D deficiency may stimulate immune cells within the bone marrow micro-environment to produce cytokines, inducing impaired erythropoiesis. Immune activation involves the reticuloendothelial system, increasing hepcidin synthesis and functional iron deficiency. Consequences of this inflammatory cascade are erythropoietin (EPO) resistance and anaemia. Given the key role of inflammation in the response to EPO, the therapeutic use of agents with anti-cytokines properties, such as vitamin D and paricalcitol, may provide benefit in the prevention/treatment of ESA hyporesponsiveness.

The association of vitamin D status with pediatric critical illness

OBJECTIVES

Vitamin D is a pleiotropic hormone important for the proper functioning of multiple organ systems. It has been hypothesized that vitamin D deficiency could contribute to or worsen outcomes in critical illness. The study objective was to determine the prevalence of vitamin D deficiency, risk factors for its presence, and potential association with clinically relevant outcomes in critically ill children.

METHODS

A prospective cohort study, conducted from 2005 to 2008 in 6 tertiary-care PICUs in Canada. Data and biological samples from 326 critically ill children up to 17 years of age were available for analysis. Total serum 25 hydroxyvitamin D or 25(OH)D was measured by using liquid chromatography-mass spectrometry.

RESULTS

The prevalence of 25(OH)D <50 nmol/L was 69% (95% confidence interval, 64-74), and 23% (95% confidence interval, 19-28) for 25(OH)D between 50 to 75 nmol/L. Lower levels were associated with hypocalcemia, catecholamine utilization, and significant fluid bolus administration. Vitamin D deficiency was independently associated with a longer PICU length of stay (+1.92 days, P = .03) and increasing severity of illness as determined by the Pediatric Risk of Mortality score with every additional point increasing the likelihood of being vitamin D deficient by 8% (P = .005).

CONCLUSIONS

This study provides evidence that vitamin D deficiency is both common among critically ill children and associated with greater severity of critical illness. Further research will determine whether targeted vitamin D supplementation or rapid restoration will improve outcome.

The impact of pretransplant 25-hydroxy vitamin D deficiency on subsequent graft function: an observational study

Background

In addition to its canonical role in musculoskeletal health, several reports have demonstrated that serum vitamin D level may influence kidney function. However, the effect of pretransplant serum vitamin D level on subsequent graft function has not been explored. Therefore, this study was undertaken to examine the effect of serum vitamin D level at the time of kidney transplantation (KT) on subsequent graft function.

Methods

We analyzed 106 patients who underwent KT and for whom 25-hydroxy vitamin D (25-OHD) levels were measured during hospitalization prior to transplantation. We measured estimated glomerular filtration rates (eGFR) using the Modification of Diet in Renal Disease (MDRD) formula at baseline and at six-month intervals up to 36 months after KT.

Results

38.7% of the patients were diagnosed with 25-OHD deficiency defined as less than 10 ng/mL. Recipient gender (female vs. male, odds ratio [OR] 3.30, 95% CI 1.33-8.21, P = 0.010), serum albumin level (per 1 mg/dl increase, OR 0.35, 95% CI 0.13-0.98, P = 0.047), and predominant renal replacement therapy modality before KT (P < 0.001) were found to be independent pretransplant risk factors for 25-OHD deficiency by multivariate logistic regression analysis. Subsequent repeated measures analysis of covariance revealed that 25-OHD level had the only significant main effect on eGFR during the 36-month follow-up period [F (1, 88) = 12.07, P = 0.001].

Conclusions

Pretransplant 25-OHD deficiency was significantly associated with a lower post-transplant eGFR, suggesting that 25-OHD may play an important role in maintaining graft function after KT.