Calf Circumference Predicts Falls in Older Adults on Hemodialysis.

OBJECTIVE: Older patients with chronic kidney disease (CKD) undergoing maintenance hemodialysis are at a higher risk of falling. However, there is no standard method to screen patients at higher risk. We have evaluated whether calf circumference (CC) measurement would be able to predict falls in this population. METHODS: This is a prospective study that enrolled patients aged ≥65 years on conventional hemodialysis, followed for 6 months. The presence of falls was associated with demographical, clinical, and biochemical data. Reduced CC was set at <34 cm for men and <33 cm for women. We evaluated physical status using Duke activity status index (DASI) and hand grip strength (HGS). RESULTS: Ninety-one patients were included (age 73.7 ± 5.4 years, 69.2% men, 56% with diabetes). Mean CC was 32.6 ± 3.7 cm, with a high prevalence of reduced CC (61.5%). During the follow-up, 13 falls were identified (1 had a fracture and died). These patients were older and heavier (P = .017 and P = .025, respectively). Most falls occurred in patients with sarcopenic obesity (BMI >27 kg/m2 plus reduced HGS or reduced CC). In a logistic regression model, reduced CC (hazard ratio (HR) 7.81, confidence interval (CI): 1.13-53.86, P = .037), higher age (HR 1.19, CI: 1.04-1.36, P = .011), and higher body weight (relative risk (RR) 1.13, CI: 1.04-1.22, P = .003) were independently associated with falls in a fully adjusted model. CONCLUSION: CC measurement, an easy and nonexpensive tool, was able to predict falls in older patients on HD. Further studies should test the inclusion of CC in a fall risk assessment in older patients on hemodialysis.

Phosphate balance during dialysis and after kidney transplantation in patients with chronic kidney disease.

PURPOSE OF REVIEW: In patients with chronic kidney disease (CKD), hyperphosphatemia is associated with several adverse outcomes, including bone fragility and progression of kidney and cardiovascular disease. However, there is a knowledge gap regarding phosphate balance in CKD. This review explores its current state, depending on the stage of CKD, dialysis modalities, and the influence of kidney transplantation. RECENT FINDINGS: Adequate phosphate control is one of the goals of treatment for CKD-mineral and bone disorder. However, ongoing studies are challenging the benefits of phosphate-lowering treatment. Nevertheless, the current therapy is based on dietary restriction, phosphate binders, and optimal removal by dialysis. In the face of limited adherence, due to the high pill burden, adjuvant options are under investigation. The recent discovery that intestinal absorption of phosphate is mostly paracellular when the intraluminal concentration is adequate might help explain why phosphate is still well absorbed in CKD, despite the lower levels of calcitriol. SUMMARY: Future studies could confirm the benefits of phosphate control. Greater understanding of the complex distribution of phosphate among the body compartments will help us define a better therapeutic strategy in patients with CKD.

Corneal and Conjunctival Calcification in a Dialysis Patient Reversed by Parathyroidectomy.

Mineral and bone metabolism disorders are relatively common among patients with end-stage renal disease on maintenance hemodialysis. Corneal and conjunctival calcification is the main extravascular site for calcification. Recently, this form of calcification has been linked to vascular calcification. Secondary hyperparathyroidism can lead to high levels of calcium and phosphorus and increase the risk of calcification. Here, we report a case of a 38-year-old female with severe hyperparathyroidism who underwent eye examination before and after parathyroidectomy. Anterior segment optical coherence tomography showed an improvement in the number and size of ocular calcifications 6 months after surgery. This case calls attention to the importance of eye examination in patients on dialysis and brings the possibility of recovery of calcification in a short-term follow-up.

Association of parathormone and alkaline phosphatase with bone turnover and mineralization in children with CKD on dialysis: effect of age, gender, and race.

BACKGROUND: Studies investigating bone histology in children with chronic kidney disease (CKD) are scarce. METHODS: Forty-two patients, mean age 11.3 ± 4.3 years with stage 5 CKD on dialysis, underwent double tetracycline labeling bone biopsy and the relationship between clinical features, biochemical markers, and bone densitometry (DXA) was investigated. RESULTS: Low bone turnover was present in 59% of patients, abnormal mineralization in 29%, and low bone volume in 7%. Higher bone formation rate was found in non-Caucasian patients, whereas abnormal mineralization occurred in older and shorter children. We found no impact of gender and etiology of renal disease in our population. Parathormone (PTH) and alkaline phosphatase (AP) showed positive associations with bone turnover. ROC curve analysis showed a fair performance of biomarkers to predict TMV status. PTH < 2 times ULN independently associated with low bone turnover (RR 5.62, 95% CI 1.01-31.24; p = 0.049), in a model adjusted for race, calcitriol dosage, and calcium. It was also associated with abnormal mineralization (RR 1.35, 95% CI 1.04-1.75; p = 0.025), in a model adjusted for BMD scores, AP, age, and calcitriol. PTH and AP significantly predicted turnover and mineralization defect, although with low specificity and sensitivity, reaching a maximum value of 64% and 67%, respectively. CONCLUSIONS: While PTH and AP were associated with turnover and mineralization, we recognize the limitation of their performance to clearly distinguish high from low/normal bone turnover and normal from abnormal mineralization. Our results reinforce the need to expand knowledge about renal osteodystrophy in pediatric population through prospective bone biopsy studies. Graphical abstract.

High-Flux versus High-Retention-Onset Membranes: In vivo Small and Middle Molecules Kinetics in Convective Dialysis Modalities.

BACKGROUND: Patients undergoing maintenance hemodialysis (HD) exhibit increased levels of uremic toxins, which are associated with poor outcomes. Recently, new dialysis membranes have allowed clearance of solutes with higher molecular weight, without significant albumin losses high-retention-onset-HD (HRO-HD). METHODS: Prospective crossover trial, in which 16 prevalent patients switched from high-flux HD (HF-HD) to online hemodiafiltration (olHDF) and HRO-HD for 4 weeks. The following variables were evaluated: pre- and post-dialysis serum concentrations of albumin, urea, phosphate (P), beta-2 microglobulin (ß2M), and total mass (TM) extraction and dialyzer clearance of urea, P, and ß2M. RESULTS: Comparing HF-HD, olHDF, and HRO-HD, respectively, there were no differences regarding pre-dialysis serum concentrations of albumin (3.94 ± 0.36, 4.06 ± 0.22, and 3.93 ± 0.41 g/dL, p = 0.495), urea (166 ± 29, 167 ± 30, and 164 ± 27 mg/dL, p = 0.971), P (4.9 ± 2.1, 5.2 ± 1.6, and 4.9 ± 2.1 mg/dL, p = 0.879), and ß2M (31.3 ± 7.1, 32.6 ± 8.6, and 33.7 ± 5.9 µg/mL, p = 0.646). ß2M clearance was significantly lower in HF-HD in comparison to both olHDF and HRO-HD: 43 (37-53) versus 64 (48-85) mL/min, p = 0.013, and 69 (58-86) mL/min, p = 0.015, respectively. Post-dialysis ß2M serum concentration was higher in HF-HD in comparison to olHDF and HRO-HD: 11.6 (9.6-12.4) vs. 5.7 (4.5-7.0) µg/mL, p = 0.001, and 5.6 (5.3-7.6) µg/mL, p = 0.001, respectively. TM extraction of urea, P, and ß2M were similar across the 3 dialysis modalities. CONCLUSIONS: olHDF and HRO-HD were superior to HF-HD regarding ß2M clearance, leading to lower post-dialysis ß2M levels.

Mortality of Patients on Maintenance Hemodialysis Submitted to Coronary Artery Bypass Surgery.

BACKGROUND: Patients with chronic kidney disease (CKD) are less likely to be submitted to coronary artery bypass grafting (CABG) then clinical medical treatment based on the potential high risk of mortality. However, whether patients on maintenance dialysis who underwent an elective CABG experience high hospital- and long-term mortality is still debatable. METHODS: This is a prospective observational study that evaluated patients who underwent elective CABG. Three groups were compared: reference (n = 167, estimated glomerular filtration rate [eGFR] ≥60 mL/min/1.73 m2), CKD3-4 (n = 84, eGFR 15-59 mL/min/1.73 m2), and maintenance hemodialysis (n = 31). Demographic, clinical, biochemical, fluid balance data, and Sequential Organ Failure Assessment (SOFA) scores were assessed daily for the same observer from day 1 (surgery) to hospital discharge. RESULTS: The main outcomes were in-hospital and 1-year mortality. Patients aged 63 ± 10, 63 ± 8, and 65 ± 6 years old, in reference, CKD3-4, and dialysis groups, respectively (p = 0.605). Patients from the reference group had a lower prevalence of diabetes (p = 0.010) and hypertension (p = 0.021). SOFA scores were higher in CKD3-4 and dialysis groups (p = 0.001), though this difference disappeared without the renal component (p = 0.326). In-hospital mortality (n = 17) was similar across groups (p = 0.955). There was no difference in 1-year mortality among groups even after adjustments for age, diabetes, intraoperative blood loss, and time on ventilation. CONCLUSIONS: CABG short-term mortality seems not to be greater among selected patients on maintenance dialysis. A multidisciplinary team has been helping cardiologists and cardiac surgeons in the decision-making process regarding the best approach in coronary artery disease, and CABG should be considered a worthy therapeutic option.

Design and methodology of the Aging Nephropathy Study (AGNES): a prospective cohort study of elderly patients with chronic kidney disease.

BACKGROUND: Renal replacement therapy (RRT) is usually indicated for patients with chronic kidney disease (CKD) with glomerular filtration rate below 10 ml/ml/min/1.73m2. However, the need for RRT and timing of dialysis initiation are debatable for patients aged 70 years or older. We here describe the study design and methodology of the Aging Nephropathy Study (AGNES) protocol that aims at evaluating to what extent geriatric-related conditions such as frailty, cognitive dysfunction, and presence of comorbidities have an impact on survival and RRT initiation in this group of patients. In this manuscript we provide detailed information about the AGNES study design and methodology. METHODS: AGNES is a prospective observational cohort that aim to investigate clinical, biochemical and demographic factors associated with RRT initiation and mortality of patients with CKD stage 4 or 5 who are aged 70 years and older. We plan to include 200 patients over 5 years. Clinically stable outpatients on conservative management for at least 6 months will be recruited from the Nephrogeriatric Clinic at the Hospital das Clinicas da Universidade de Sao Paulo, Brazil. Eligible patients are submitted to a full clinical examination, geriatric assessment, and blood test at baseline. Following the baseline visit the patients are being monitored during an observational follow up period of at least 12 months during which patients will be contacted in the clinic at their regular follow up or by phone until either RRT initiation or death occurs. This cohort includes evaluation of cognition by the education-adjusted 10-point Cognitive Screener (10-CS), frailty by Fried index score, a complete nutritional assessment (by body composition assessment, global subjective assessment and dietary intake), comorbidities by Charlson comorbidity index and biochemical markers including FGF-23 and Klotho. DISCUSSION: The AGNES cohort, a real-world study of current clinical practice in elderly patients with advanced CKD prior to dialysis initiation, will shed light into progression of CKD and its complications, indications of RRT and factors determining survival. This investigation will elucidate to what extent geriatric conditions, nutritional status and clinical factors are associated with survival, quality of life and RRT initiation in elderly CKD patients not yet on dialysis. TRIAL REGISTRATION: Registered on ClinicalTrials.gov on 18 October 2019 ( NCT04132492 ).

Dialysis as a Treatment Option for a Patient With Normal Kidney Function and Familial Tumoral Calcinosis Due to a Compound Heterozygous FGF23 Mutation.

Primary tumoral calcinosis is a rare autosomal recessive disorder characterized by ectopic calcified tumoral masses. Mutations in 3 genes (GALNT3, FGF23, and KL) have been linked to this human disorder. We describe a case of a 28-year-old man with a history of painful firm masses over his right and left gluteal region, right clavicle region, knees, and left elbow. Biochemical analysis disclosed hyperphosphatemia (phosphate, 9.0 mg/dL) and normocalcemia (calcium, 4.8 mg/dL), with normal kidney function and fractional excretion of phosphate of 3%. Parathyroid hormone was suppressed (15 pg/mL), associated with a low-normal 25-hydroxyvitamin D (26 ng/mL) concentration but high 1,25-dihydroxyvitamin D concentration (92 pg/mL). Serum intact FGF-23 (fibroblast growth factor 23) was undetectable. Genetic analysis revealed tumoral calcinosis due to a compound heterozygous mutation in FGF23, c.201G>C (p.Gln67His) and c.466C>T (p.Gln156*). Due to lack of other treatment options and because the patient was facing severe vascular complications, we initiated a daily hemodialysis program even in the setting of normal kidney function. This unusual therapeutic option successful controlled hyperphosphatemia and reduced metastatic tumoral lesions. This is a report of a new mutation in FGF23 in which dialysis was an effective treatment option for tumoral calcinosis with normal kidney function.

Phosphate Removal During Conventional Hemodialysis: a Decades-Old Misconception.

BACKGROUND/AIMS: Hyperphosphatemia is associated with high mortality rate in patients on dialysis. Conventional hemodialysis (HD) is a limit technique in removing phosphate (P). There is a widespread belief that P is removed mainly in the first hour of HD. The aim of this study was to certify the percentage of 1-hour removal of P as compared to the entire procedure. METHODS: data from the first dialysis of the week of 21 patients (13 men, age 44±15 years), for 3 consecutive dialysis sessions were evaluated. Fresh dialysate samples were collected at 1 hour and at the end of the session from a partial spent dialysate collection method. RESULTS: Pre dialysis serum P was 4.7±1.7 mg/dl. Reduction rate of serum P was 47.4 ± 14.3 and 45.1 ± 10.8% in 1- and 4-hour of HD, respectively (p=0.322). P removal was 194 (145, 242) mg in 1-hour (p<0.0001), which represents 25.0 ± 0.2% of the total removed during the entire HD. Patients with pre dialysis P ≥ 5.5mg/dl had higher P removal during HD than those with P < 5.5mg/dl [975 (587, 1354) vs. 776 (580, 784) mg, p=0.025], although the percentage of removal in 1 hour was not different from those with P < 5.5mg/d (24.9 ± 0.3 vs. 25.0 ± 0.1%, p=0.918). P removal during dialysis correlated with pre dialysis serum P (r=0.455, p=0.001), parathormone (r=0.264, p=0.037) and ultrafiltration volume (r=0.343, p=0.019). CONCLUSION: despite the P serum concentration normalizing in the first hour of hemodialysis, the removal in the same period reaches only 25% of the entire session.

Early Start Peritoneal Dialysis: Technique Survival in Long-Term Follow-Up.

BACKGROUND/AIMS: Peritoneal dialysis (PD) has gained interest over the last decade as a viable option for early start dialysis. It is still unknown if shorter break-in periods and less time for proper patient evaluation and training could influence technique survival in comparison to planned-start PD. METHODS: A prospective and observational study that compared technique survival in a cohort of patients who started either early or planned PD. Early start PD was defined as break-in period from 3 to 14 days with no previous nephrologist follow-up or patient training. RESULTS: A total of 154 patients were included (40 as early start PD), followed by a median time of 381 days. Comparing early vs. planned-start PD, groups were similar concerning age 56 (40; 70) vs. 48 (32; 63) years, p=0.071, body mass index (BMI) 23.3 ± 4.2 vs. 23.8 ± 4.0 kg/m2, p=0.567 and male gender (60 vs. 48%, p=0.201), respectively. Comparing early vs. planned-start groups, there were no differences regarding PD dropout for peritonitis (7.5 vs. 11.4%, p=0.764), catheter dysfunction (12.5 vs. 17.5%, p=0.619) and patient burnout (0 vs. 4.4%, p=0.328), respectively. Less patients in early start group quit PD for peritoneal membrane failure in comparison to planned-start group (2.5 vs. 16.7%, p=0.026). In multivariate cox-regression analysis, the only factors independently associated with technique failure were BMI> 25 kg/m² (p=0.033) and Diabetes Mellitus (p=0.013), whereas no differences regarding early vs. planned-PD start were observed (p=0.184). CONCLUSION: Despite the adverse scenario for initiating dialysis, early start PD had similar outcomes in comparison to planned-start PD in long-term follow-up.

Decision-making process in the pre-dialysis CKD patients: do anxiety, stress and depression matter?

BACKGROUND: The transition from pre-dialysis chronic kidney disease (CKD) to renal replacement therapy (RRT) is a stressful event. Anxiety, depression and stress are frequent conditions in this population, and might play a role on the choice of dialysis modality. METHODS: This is a prospective study that included stages 4-5 CKD patients during a dialysis multi-disciplinary education program. Demographic, clinical, and laboratory data were evaluated. Hospital Anxiety and Depression Scale and a Perceived Stress Scale assessed levels of anxiety, depression and stress, respectively. RESULTS: A total of 67 from 190 recruited patients were included (59 ± 15 years, 54% males). Comparing patients who chose peritoneal dialysis (PD) and hemodialysis (HD), there were no differences on anxiety (p = 0.55), and depression scores (p = 0.467), and stress (p = 0.854). Anxious (p = 0.007) and depressive (p = 0.030) patients presented lower levels of phosphate than those not affected. There was a significant correlation (p < 0.0001) between anxiety and depression scores (R2 = 0.573), anxiety and stress scores (R2 = 0.542), depression and stress scores (R2 = 0.514). At the end of study, 29.8% of patients had already started on dialysis, and scores of anxiety, depression and stress reduced significantly (all p values < 0.0001), from 5.9 ± 3.3 to 1.8 ± 1.8, from 7.7 ± 4.0 to 3.8 ± 2.9 and from 28.6 ± 7.8 to 10.0 ± 6.2, respectively, regardless of which therapy was chosen. CONCLUSION: Depression, anxiety and perceived stress during final stages of CKD do not seem to be related to the choice of dialysis therapy and tend to decrease after dialysis initiation.

The complexity of chronic kidney disease-mineral and bone disorder across stages of chronic kidney disease.

Chronic Kidney Disease (CKD)-Mineral and Bone Disorder (CKD-MBD) is a complex disease that is not completely understood. However, some factors secreted by the osteocytes might play an important role in its pathophysiology. Therefore, we evaluated the bone expression of proteins in a group of patients with CKD 2-3, CKD 4, and CKD 5 on dialysis and healthy individuals. We also tested several bone remodeling markers, and correlated these levels with bone biopsy findings. As expected, as serum calcium decreased, serum phosphate, alkaline phosphatase, fibroblast growth factor-23 (FGF-23), parathyroid hormone, and osteoprotegerin increased, as CKD progressed. Additionally, there was a gradual increase in bone resorption associated with a decrease in bone formation and impairment in bone mineralization. Bone expression of sclerostin and parathyroid hormone receptor-1 seemed to be increased in earlier stages of CKD, whereas FGF-23 and phosphorylated ß-catenin had increased expression in the late stages of CKD, although all these proteins were elevated relative to healthy individuals. Immunohistochemical studies showed that FGF-23 and sclerostin did not co-localize, suggesting that distinct osteocytes produce these proteins. Moreover, there was a good correlation between serum levels and bone expression of FGF-23. Thus, our studies help define the complex mechanism of bone and mineral metabolism in patients with CKD. Linkage of serum markers to bone expression of specific proteins may facilitate our understanding and management of this disease.

Serum levels of fibroblast growth factor 23 are elevated in patients with active Lupus nephritis.

BACKGROUND: Fibroblast growth factor 23 (FGF23), a phosphate-regulating hormone is an established cardiovascular risk factor. Recently, FGF23 has been related to inflammation. Lupus is an inflammatory disease, and whether FGF23 is associated with Lupus nephritis (LN) activity is unknown. MATERIALS AND METHODS: We studied 15 pre-menopausal patients with recent LN diagnose (⩽2months) and compared them to 1:1 age-matched healthy control group. We measured serum levels of intact FGF23, interleukin-6 (IL-6), tumor necrosis factor α (TNFα), and urinary levels of monocyte chemotactic protein (MCP1). RESULTS: LN patients (29.5±10years) presented proteinuria of 4.7±2.9g/day, and estimated glomerular filtration rate of 37 (31-87)ml/min/1.73m2. They demonstrated higher FGF23 levels when compared to healthy controls [106.7 (80.3-179) vs. 33.6 (25.8-60.9) pg/ml, p<0.001]. FGF23 levels correlated with urinary MCP1 (r=0.62, p<0.001), serum TNFα (r=0.58, p<0.001) and serum IL-6 (r=0.46, p=0.01). Only the correlation between FGF23 and MCP1 remained significant after adjustments for 25(OH) vitamin D and renal function. CONCLUSION: Newly diagnosed LN patients demonstrated elevated FGF23 levels that were positively correlated to urinary MCP1, independently of vitamin D levels and kidney function. If FGF23 may predict clinical outcomes in LN warrants further evaluation.

Pneumatic Compression, But Not Exercise, Can Avoid Intradialytic Hypotension: A Randomized Trial.

BACKGROUND: Conventional hemodialysis (HD) is associated with dialysis-induced hypotension (DIH) and ineffective phosphate removal. As the main source of extracellular fluid removed during HD are the legs, we sought to reduce DIH and increase phosphate removal by using cycling and pneumatic compression, which would potentially provide higher venous return, preserving central blood flow and also offering more phosphate to the dialyzer. METHODS: We evaluated 21 patients in a randomized crossover fashion in which each patient underwent 3 different HD: control; cycling exercise during the first 60 min; and pneumatic compression during the first 60 min. Data obtained included bioelectrical impedance, hourly blood pressure measurement, biochemical parameters, and direct quantification of phosphate through the dialysate. DIH was defined as a drop in mean arterial pressure (MAP) ≥20 mm Hg. RESULTS: There was no difference in the ultrafiltration rate (p = 0.628), delta weight (p = 0.415), delta of total, intra and extracellular body water among the control, cycling, and pneumatic compression (p = 0.209, p = 0.348, and p = 0.467 respectively). Delta MAP was less changed by pneumatic compression when compared to control, cycling, and pneumatic compression respectively (-4.7 [-17.2, 8.2], -4.7 [-20.5, -0.2], and -2.3 [-8.1, 9.0] mm Hg; p = 0.021). DIH occurred in 43, 38, and 24% of patients in control, cycling, and pneumatic compression respectively (p = 0.014). Phosphate removal did not increase in any intervention (p = 0.486). Higher phosphate removal was dependent on ultrafiltration, pre dialysis serum phosphate, and higher parathyroid hormone. CONCLUSION: Pneumatic compression during the first hour of dialysis was associated with less DIH, albeit there was no effect on fluid parameters. Neither exercise nor pneumatic compression increased phosphate removal.

Furosemide Increases the Risk of Hyperparathyroidism in Chronic Kidney Disease.

BACKGROUND: Diuretics are widely used in patients with chronic kidney disease (CKD). While thiazide-like diuretics limit urinary calcium excretion, loop diuretics (LD) promote calcium wasting, which might facilitate the development of secondary hyperparathyroidism (HPT2). We sought to investigate, in CKD patients not on dialysis, the influence of either hydrochlorothiazide (Hydro) or furosemide (Furo) on circulating parathyroid hormone (PTH) and whether such actions are determined by the effects of these compounds on calcium excretion. METHODS: Electronic charts of all nephrology outpatients (CKD stages 2-5) who were given Hydro or Furo were included. We assessed estimated glomerular filtration rate (eGFR), biochemical parameters and 24-hour calcium excretion. Hyperparathyroidism was defined as PTH >65 pg/ml. RESULTS: Out of 275 patients, 108 (29%) were taking Hydro and 167 (61%) Furo. Patients on Hydro were younger, mostly female and had higher eGFR. The median 24-hour urinary calcium excretion in the overall cohort was 41 (22, 76), being lower in Furo than in Hydro patients (37 (16, 68) vs. 47 (26, 88) mg/24 h, respectively, p = 0.016). Logistic regression showed that, after adjustment for eGFR, calcium excretion rate was found not to increase the risk ratio for HPT2, whereas Furo was a strong predictor of HPT2. CONCLUSION: Furo increased the risk of HPT2 among CKD patients compared to Hydro. This effect was independent of eGFR or calcium excretion. The use of LD in CKD, currently preferred in advanced stages, should be reappraised.

High Dialysate Calcium Concentration May Cause More Sympathetic Stimulus During Hemodialysis.

BACKGROUND/AIMS: Acute activation of sympathetic activation during hemodialysis is essential to maintain blood pressure (BP), albeit long-term overactivity contributes to higher mortality. Low heart rate variability (HRV), a measure of autonomic nervous system activity, and abnormal ankle-brachial index (ABI) are associated with higher mortality in patients on hemodialysis. In this study, we assessed HRV and ABI pre and post dialysis in incident patients on hemodialysis using high (1.75mmol/l) and low (1.25mmol/l) dialysate calcium concentration (DCa). METHODS: HRV was measured as the ratio between low frequency and high frequency power (LF/HF). Thirty patients (age 47±16 years, 67% men) were studied in two consecutive mid-week hemodialysis sessions. RESULTS: Mean BP variation was positive with DCa 1.75 and negative with DCa 1.25 [4.0 (-6.0, 12.2 mmHg) vs. -3.2 (-9.8, 1.3 mmHg); p=0.050]. Reduction of ABI from pre to post HD was related to higher sympathetic activity (p=0.031). The increase in LF/HF ratio was higher with DCa 1.75 (58.3% vs. 41.7% in DCa 1.75 and 1.25, respectively, RR 2.8; p=0.026). CONCLUSION: Although higher DCa is associated with better hemodynamic tolerability during hemodialysis, this occurs at the expense of increased sympathetic activity. Higher sympathetic activity was associated with a decrease of ABI during hemodialysis.

Is urinary density an adequate predictor of urinary osmolality?

BACKGROUND: Urinary density (UD) has been routinely used for decades as a surrogate marker for urine osmolality (Uosm). We asked if UD can accurately estimate Uosm both in healthy subjects and in different clinical scenarios of kidney disease. METHODS: UD was assessed by refractometry. Uosm was measured by freezing point depression in spot urines obtained from healthy volunteers (N = 97) and in 319 inpatients with acute kidney injury (N = 95), primary glomerulophaties (N = 118) or chronic kidney disease (N = 106). RESULTS: UD and Uosm correlated in all groups (p < 0.05). However, a wide range of Uosm values was associated with each UD value. When UD was ≤ 1.010, 28.4% of samples had Uosm above 350 mOsm/kg. Conversely, in 61.6% of samples with UD above 1.020, Uosm was below 600 mOsm/kg. As expected, Uosm exhibited a strong relationship with serum creatinine (Screat), whereas a much weaker correlation was found between UD and Screat. CONCLUSION: We found that UD is not a substitute for Uosm. Although UD was significantly correlated with Uosm, the wide dispersion makes it impossible to use UD as a dependable clinical estimate of Uosm. Evaluation of the renal concentrating ability should be based on direct determination of Uosm.