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.

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.

CKD-EPI versus Cockcroft-Gault formula for predicting contrast-induced nephropathy following percutaneous coronary intervention in patients without significant renal impairment. / Fórmula de CKD­EPI versus Cockcroft­Gault na predição de nefropatia induzida por contraste após intervenção coronária percutânea, em pacientes sem disfunção renal significativa.

INTRODUCTION: Individuals with glomerular filtration rate (GFR) ≥60 ml/min/1.73 m2 estimated by the Cockcroft-Gault formula (CG) who undergo percutaneous coronary intervention (PCI) frequently develop contrast-induced nephropathy (CIN). This study aimed to assess whether individuals with significant renal impairment assessed by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula, but not by CG, more often develop CIN following PCI than those without renal impairment by either formula. METHODS: In this cross-sectional study analyzing patients with baseline CG GFR ≥60 ml/min/1.73 m2 before PCI, subjects were divided into two groups according to CIN occurrence. Baseline CKD-EPI GFR was calculated for all patients. RESULTS: We analyzed 140 patients. Baseline GFR was 87.5±21.3 and 77.1±15.0 ml/min/1.73 m2 for CG and CKD-EPI, respectively. CIN occurred in 84.6% of individuals with baseline CKD-EPI GFR <60 ml/min/1.73 m2 vs. 51.1% of those without. Males and those with higher body mass index were more likely to present baseline CKD-EPI GFR <60 ml/min/1.73 m2 (p=0.021). Non-ionic contrast agent use and baseline CKD-EPI GFR ≥60 ml/min/1.73 m2 were protective factors against CIN. Greater amounts of contrast agent and acute coronary syndrome were associated with higher CIN risk. In subjects with serum creatinine <1.0 mg/dl, GFR was more likely to be overestimated by CG, but not by CKD-EPI (sensitivity 100.0%; specificity 52.0%). CONCLUSION: In patients undergoing PCI without renal dysfunction by CG, a finding of CKD-EPI GFR <60 ml/ min/1.73 m2 was associated with a higher probability of CIN, especially among men and those with higher body mass index.

Fórmula de CKD-EPI versus Cockcroft-Gault na predição de nefropatia induzida por contraste após intervenção coronária percutânea, em pacientes sem disfunção renal significativa

Introdução: Nefropatia induzida por contraste (NIC) após intervenção coronária percutânea (ICP) em pacientes com taxa de filtração glomerular (TFG) ≥ 60 mL/min, estimada pela equação de Cockcroft-Gault (C-G), não é infrequente. O objetivo desse estudo foi avaliar a capacidade da equação CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) em predizer NIC em indivíduos sem disfunção renal significativa basal pela fórmula C-G. Métodos: Incluídos pacientes submetidos a ICP entre 2008-2013, com TFG basal ≥ 60 mL/min pela equação de C-G. Estes indivíduos foram divididos em dois grupos, conforme ocorrência ou não de NIC. Para todos os casos, foi calculada a TFG basal conforme a equação do CKD-EPI. Resultados: A amostra consistiu de 140 pacientes. A TFG C-G basal foi de 87,5 ± 21,3 mL/mine de 77,1 ± 15,0 mL/min/1,73 m2para CKD-EPI. NIC ocorreu em 84,6% dos pacientes com TFG CKD-EPI basal < 60 mL/min/1,73 m2, contra 51,1% daqueles com TFG CKD-EPI basal ≥ 60 mL/min/1,73 m2(p = 0,021). Indivíduos masculinos ou com peso corporal elevado apresentaram mais frequentemente TFG CKD-EPI basal < 60 mL/min/1,73 m2. Contraste não--iônico e TFG CKD-EPI basal ≥ 60 mL/min/1,73 m2foram fatores protetores à ocorrência de NIC. Em indivíduos com creatinina < 1,0 mg/dL, o achado de TFG superestimada por C-G, mas não pelo CKD-EPI, foi mais frequente (sensibilidade de 100,0%; especificidade de 52,0%). Conclusões: Em pacientes sem disfunção renal por C-G, submetidos a ICP, o achado de TFG CKD--EPI < 60 ml/min/1,73 m2implicou em maior chance de NIC, principalmente entre indivíduos do sexo masculino e de maior massa corpórea.