¿Mejora la aproximación físico-química de Stewart-Fencl la valoración del equilibrio ácido-base en pacientes estables en hemodiafiltración? / Does Stewart-Fencl approach improve the evaluation of acidbase status in stable patients on hemodiafiltration?

Introducción: la evaluación del equilibrio ácido-base se basa en la ecuación de Henderson-Hasselbach. En 1983, P. Stewart desarrolló un análisis cuantitativo del equilibrio ácido-base en el que muestra un sistema con unas variables independientes entre las que se incluyen pCO2, diferencia iónica fuerte medida (SIDm), es decir, la diferencia entre la suma de cationes fuertes (Na+, K+, Ca++, Mg++) y la suma de aniones fuertes (Cl–, lactato) y la concentración total de todos los aniones débiles no volátiles (ATot), cuyos principales representantes son el fósforo inorgánico (P–) y la albúmina (Albúm.–). El objetivo de este estudio es evaluar desde ambas perspectivas el equilibrio ácido-base en pacientes en hemodiafiltración (HDF) crónica. Material y métodos: se estudian 35 pacientes (24 hombres y 11 mujeres, con una edad media de 67,2 ± 15,7 años y con un peso seco de 72,8 ± 19,2 kg. La duración media de la hemodiálisis (HD) fue de 253,6 ± 40,5 minutos. Se analizan los parámetros gasométricos (pH, pCO2, HCO3–y exceso de bases) y Na+, K+, Cl–, Ca++, Mg++ y lactato. Se calcularon la SIDm, la SIDe mediante la fórmula de Figge (1.000 x 2,46–11 x pCO2 /[10 – pH] + Albúm. g/dl x [0,123 x pH –0,631] + P en mmol/l x [0,309 x pH –0,469)] y gap del SID (SIDm-SIDe). Resultados: el pH pre-HD fue de 7,36 ± 0,08 y el pH post-HD de 7,44 ± 0,08 (p <0,001). No se apreciaron diferencias significativas entre pCO2 pre y post-HD. El HCO3 – y el exceso de bases se incrementaron durante la sesión (p <0,001). La SIDm descendió de manera significativa de 46,2 ± 2,9 preHD a 45 ± 2,3 post-HD (p <0,05). Por el contrario, la SIDe se elevó de 38,5 ± 3,8 a 42,9 ± 3,1 (p <0,001). El anion gap descendió de 18,6 ± 3,8 pre-HD a 12,8 ± 2,8 Eq/l post-HD (p <0,001) y el gap del SID de 7,6 ± 3 a 2,1 ± 2 (p <0,001). Se apreció una correlación entre el anion gap y el gap-SID tanto antes como después de la HDF. Asimismo, se apreció una correlación significativa entre el ?? exceso de bases y ?? del gap-SID. Conclusión: en conclusión, la aproximación físico-química de Stewart-Fencl no mejora la valoración del equilibrio ácido-base en pacientes en HDF crónica. En presencia de normocloremia la SIDm no refleja el proceso alcalinizante de la sesión de hemodiálisis. Bajo esta perspectiva, la sesión de hemodiálisis se concibe como una retirada de aniones inorgánicos no metabolizables, en especial el sulfato. El espacio dejado por estos aniones es reemplazado por OH–y secundariamente por HCO3–. La única ventaja vendría dada por una mejor valoración de los aniones no medidos mediante el gap del SID, sin el efecto de la albúmina y el fosfato (AU)

Introduction: The traditional evaluation of acid-base status relies on the Henderson-Hasselbach equation. In 1983, an alternative approach, based on physical and chemical principles was proposed by P. Stewart. In this approach, plasma pH is determined by 3 independent variables: pCO2, Strong Ion Difference (SIDm), which is the difference between the strong cations (Na+, K+, Ca++, Mg++) and the strong anions (Cl–, lactate) and total plasma concentration of nonvolatile weak acids (ATot), mainly inorganic phosphate and albumin. Bicarbonate is considered a dependent variable. The aim of this study was to evaluate the acid-base status using both perspectives, physical chemical and traditional approach. Material and methods: we studied 35 patients (24 male; 11 female) on hemodiafiltration, mean age was 67.2 ± 15.7, 8 ± 19.2 kg. We analyzed plasma chemistry including pH, pCO2, HCO3–, base excess and Na+, K+, Cl–, Ca++, Mg++, lactate and SIDm. The SID estimated (SIDe) was calculated by Figge’s formula (1,000 x 2.46–11 x pCO2/[10 – pH] + Album g/dl x [0.123 x pH –0.631] + P in mmol/l0 x [0.309 x pH –0.469]) and Gap of the SID as the difference SIDm-SIDe. Results: pH preHD was 7.36 ± 0.08 and pH post-HD 7.44 ± 0.08 (p <0.001). There was no significant differences between pCO2 pre- and post-HD. HCO3– and base excess increased during the session (p <0.001). SIDm decreased from 46.2 ± 2.9 pre-HD to 45 ± 2.3 mEq/l post-HD (p <0.05). On the opposite, SIDe increased from 38.5 ± 3.8 to 429 ± 3.1 mEq/l (p <0.001). The Gap Anion descended from 18.6 ± 3.8 pre-HD to 12.8 ± 2.8 mEq/l post-HD (p <0.001) and the Gap of the SID 7.6 ± 3 to 2.1 ± 2 (p <0.001). Anion Gap correlated with the Gap-SID so much pre-HDF as pos-HDF. ?? Base excess correlated only with ?? of the Gap SID. Conclusion: Stewart-Fencl’s approach does not improve characterization of acid-base status in patients on chronic HDF. In presence of normocloremia the SIDm does not reflect the alkalinizing process of the session of hemodialysis. According this approach, hemodialysis therapy can be viewed as a withdrawal of inorganic anions, especially the sulphate. These anions are replaced by OH– and secondarily for HCO3–. The approach only improves the evaluation of unmeasured anions by the Gap of the SID, without the effect of albumin and phosphate (AU)

[Does Stewart-Fencl improve the evaluation of acid-base status in stable patients on hemodiafiltration?]. / ¿Mejora la aproximación físico-química de Stewart-Fencl la valoración del equilibrio ácido-base en pacientes estables en hemodiafiltración?

INTRODUCTION: The traditional evaluation of acid-base status relies on the Henderson-Hasselbach equation. In 1983, an alternative approach, based on physical and chemical principles was proposed by P. Stewart. In this approach, plasma pH is determined by 3 independent variables: pCO2, Strong Ion Difference (SIDm), which is the difference between the strong cations (Na +, K +, Ca ++, Mg ++) and the strong anions (Cl-, lactate) and total plasma concentration of nonvolatile weak acids (ATot), mainly inorganic phosphate and albumin. Bicarbonate is considered a dependent variable. The aim of this study was to evaluate the acid-base status using both perspectives, physical chemical and traditional approach. MATERIAL AND METHODS: We studied 35 patients (24 M; 11F) on hemodiafiltration, mean age was 67,2+/-15,7, 8+/-19,2 kg. We analyzed plasma chemistry including pH, pCO2, HCO3-, base excess and Na+, K+, Cl-, Ca++, Mg++, lactate and SIDm. The SID estimated (SIDe) was calculated by Figge's formula (1000 x 2.46E-11 x pCO2 / (10-pH) + Album gr/dl x (0.123 x pH-0.631) + P in mmol/l x (0.309 x pH-0.469) and Gap of the SID as the difference SIDm-SIDe. RESULTS: pH preHD was 7,36+/-0,08 and pH posHD 7,44+/-0,08 (p < 0.001). There was no significant differences between pCO2 pre and pos-HD. HCO3 - and base excess increased during the session (p < 0.001). SIDm decreased from 46,2+/-2,9 preHD to 45+/-2,3 mEq/l postHD (p < 0.05). On the opposite, SIDe increased from 38,5+/-3,8 to 42,9+/-3,1 mEq/l (p < 0.001). The Gap Anion descended from 18,6+/-3,8 preHD to 12,8+/-2,8 mEq/l mEq/l postHD (p < 0.001) and the Gap of the SID 7,6+/-3 to 2,1+/-2 (p < 0.001). Anion Gap correlated with the Gap-SID so much pre-HDF as pos-HDF. Delta Base excess correlated only with Delta of the Gap SID. CONCLUSION: Stewart-Fencl's approach does not improve characterization of acid-base status in patients on chronic HDF. In presence of normocloremia the SIDm does not reflect the alkalinizing process of the session of hemodialysis. According this approach, hemodialysis therapy can be viewed as a withdrawal of inorganic anions, especially the sulphate. These anions are replaced by OH - and secondarily for HCO3-. The approach only improves the evaluation of unmeasured anions by the Gap of the SID, without the effect of albumin and phosphate.

Switching from three times a week to short daily online hemodiafiltration: effects on acid-base balance.

AIMS: This study examines the effect of a change from the standard 4-5 hours 3 times a week of online hemodiafiltration (OL-HDF) to 2-2.5 hours daily (6 times a week) OL-HDF, on acid-base balance, and attempts assess the modifications of acid-base parameters, ionic concentration, and electrical charges of albumin and phosphate available for diffusion and convection mechanisms across the membrane and subsequent infusion. METHODS: In 18 patients on online HDF, blood gas, electrolytes (Na, K, Cl), lactate, phosphate, albumin, apparent strong ion difference (SIDa), effective strong ion difference (SIDe), strong ion gap (SIG), anion gap (AG), and bicarbonate and pH time-averaged concentration (TAC) and time-averaged deviation (TAD) variables were evaluated at baseline, and 1, 3, 6, 9, and 12 months after patients were switched to daily OL-HDF. Additionally, in 12 patients, the same parameters measured simultaneously at dialyzer inlet, outlet, and after reinfusion were studied. RESULTS: Throughout the study, weekly single-pool Kt/V, equilibrated Kt/V, and TAC urea remained constant. However, standard Kt/V increased and TAD urea decreased on daily OL-HDF. There were no statistical differences during the time span of 12 months in pH, cations (Na, K), anions (Cl, HCO3(-) AG, and lactate), or SIDa, SIDe, and SIG pre-HDF; while pH and HCO3(-) TAD decreased from 0.02 and 1.02 +/- 0.74 mEq/L, to 0.01 and 0.64 +/- 0.52 mEq/L, respectively (p<0.01). Net albumin charge and AG increased significantly at dialyzer outlet and decreased after reinfusion. CONCLUSIONS: We did not observe changes in the acid-base balance in patients who switched from 3 times a week to short daily OL-HDF. The main benefit observed was a lower pH and bicarbonate TAD. This shows a better physiology for daily OL-HDF.

[Determination of the dose of dialysis with integrated modules in the same monitor]. / Medición de la dosis de diálisis mediante diferentes módulos integrados en un mismo monitor.

The "gold standard" method to measure the mass balance achieved during dialysis for a given solute is based on the total dialysate collection. This procedure is unfeasible and too cumbersome. For this reason, alternative methods have been proposed including the urea kinetic modelling (Kt/V), the measurement of effective ionic dialysance (Diascan), and the continuous spent sampling of dialysate (Quantiscan). The aim of this study was to compare the reliability and agreement of these two methods with the formulas proposed by the urea kinetic modelling for measuring the dialysis dose and others haemodialysis parameters. We studied 20 stable patients (16 men/4 women) dialyzed with a monitor equipped with the modules Diascan (DC) and Quantiscan (QC) (Integra. Hospal). The urea distribution volume (VD) was determined using anthropometric data (Watson equation) and QC data. Kt/V value was calculated according to Daurgidas 2nd generation formula corrected for the rebound (eKt/V), and using DC (Kt/VDC) and QC (Kt/VQC) data. The total mass of urea removed was calculated as 37,93 +/- 16 g/session. The VD calculated using Watson equation was 35.7 +/- 6.6 and the VDQC was 35.06 +/- 9.9. And they showed an significative correlation (r:0,82 p < 0.001). The (VDQC-VDWatson) difference was -0.64 +/- 5.8L (ns). Kt/VDC was equivalent to those of eKt/V (1.64 +/- 0.33 and 1.61 +/- 0.26, mean difference -0.02 +/- 0.29). However, Kt/VQC value was higher than eKt/V (1.67 +/- 0.22 and 1.61 +/- 0.26 mean difference 0.06 +/- 0.07 p < 0.01). Both values correlated highly (R2: 0.92 p < 0.001). Urea generation (C) calculated using UCM was 8.75 +/- 3.4 g/24 h and those calculated using QC was 8.64 +/- 3.21 g/24 h. Mean difference 0.10 +/- 1.14 (ns). G calculated by UCM correlated highly with that derived from QC (R2: 0.88 p < 0.001). In conclusion, Kt/VDC and Kt/VQC should be considered as valid measures for dialysis efficiency. However, the limits of agreement between Kt/VQC and eKt/V were closer than Kt/VDC.

Medición de la dosis de diálisis mediante diferentes módulos integrados en un mismo monitor / Determination of the dose of dialysis with integrated modules in the same monitor

La recolección total del líquido de diálisis para cuantificar la cantidad total deurea eliminada durante la hemodiálisis (HD) se ha considerado la técnica «goldestándar» para medir la dosis de diálisis. Dada la dificultad de este método sehan propuesto otros alternativos como el modelo cinético de la Urea (Kt/V), lamedición de la dialisancia iónica o la recogida de muestras representativas del líquidode diálisis total.El objetivo de este trabajo es comparar la fiabilidad y concordancia de dos dispositivosde medida (dialisancia iónica y recogida parcial de líquido de diálisis)integrados en el mismo monitor de diálisis y compararlos con los propuestos porel modela cinético de la urea (MCU) para la medición de la dosis de diálisis(Kt/V) y otros parámetros de HD.Para ello se estudiaron 20 pacientes (16V/4M) con una edad media de 64,5 ±13 años, estables en programa de HD y dializados con el monitor Integra® (Hospal)equipado con los biosensores Diascan (DC) y Quantiscan (QC). El volumende distribución de urea (VD) se calculó a partir de la fórmula de Watson y porel QC. La generación de urea se calculó a partir del MCU y el Kt/V se determinópor la fórmula de Daurgidas 2ª generación corregida para el rebote (eKt/V),por el DC y el QC.La transferencia de masa de urea medida por QC fue de 37,2 ± 13,8 g. El VDpor la fórmula de Watson y por QC fue de 35,7 ± 6,6 y de 35,06 ± 9,9 L respectivamente(ns) y mostraron una correlación significativa (r: 0,82 p < 0,001).Los valores de aclaramiento (K), mediante DC, y QC fueron similares KQC: 230,3± 56,5 ml/min, KDC: 214,05 ± 24,3 ml/min (ns) No se apreciaron diferencias enel Kt/V calculado por DC y el eKt/V (KtVDC: 1,64 ± 0,33 vs KtVeq; 1,61 ± 0,26).El coeficiente de correlación fue de r: 0,45 (p < 0,05). Por el contrario los valoresde Kt/VQC fueron superiores a los calculados por el eKtV (1,67± 0,22 vs. 1,61± 0,26). El coeficiente de correlación fue de r: 0,94 ( p < 0,001). La generaciónde urea por el MCU fue de 8,7 ± 3,4 y por QC de 8,6 ± 3,2 g/ 24h (ns) r: 0,94p < 0,001).Podemos concluir que tanto la medición de la dialisancia iónica mediante elDC, como la recogida de muestras representativas del líquido de diálisis medianteel QC, son métodos sencillos, fiables y reproducibles que nos permiten medirde manera rápida la eficacia dialítica y otros parámetros de hemodiálisis. En nuestra experiencia la cuantificación de la dosis de diálisis mediante el QC presentauna mayor concordancia que la realizada con DC

The «gold standard» method to measure the mass balance achieved during dialysisfor a given solute is based on the total dialysate collection. This procedure isunfeasible and too cumbersome. For this reason, alternative methods have beenproposed including the urea kinetic modelling (Kt/V), the measurement of effectiveionic dialysance (Diascan), and the continuous spent sampling of dialysate(Quantiscan).The aim of this study was to compare the reliability and agreement of thesetwo methods with the formulas proposed by the urea kinetic modelling for measuringthe dialysis dose and others haemodialysis parameters.We studied 20 stable patients (16 men/4 women) dialyzed with a monitor equippedwith the modules Diascan (DC) and Quantiscan (QC) (Integra®. Hospal). Theurea distribution volume (VD) was determined using anthropometric data (Watsonequation) and QC data. Kt/V value was calculated according to Daurgidas2nd generation formula corrected for the rebound (eKt/V), and using DC (Kt/VDC)and QC (Kt/VQC) data.The total mass of urea removed was calculated as 37,93 ± 16 g/session. TheVD calculated using Watson equation was 35.7 ± 6.6 and the VDQC was 35.06± 9.9. And they showed an significative correlation (r:0,82 p < 0.001). The (VDQCVDWatson)difference was –0.64 ± 5.8L (ns). Kt/VDC was equivalent to those ofeKt/V (1.64 ± 0.33 and 1.61 ± 0.26, mean difference –0.02 ± 0.29). However,Kt/VQC value was higher than eKt/V (1.67 ± 0.22 and 1.61 ± 0.26 mean difference0.06 ± 0.07 p < 0.01). Both values correlated highly (R2: 0.92 p < 0.001).Urea generation (G) calculated using UCM was 8.75 ± 3.4 g/24 h and those calculatedusing QC was 8.64 ± 3.21 g/24 h. Mean difference 0.10 ± 1.14 (ns). Gcalculated by UCM correlated highly with that derived from QC (R2: 0.88 p <0.001).In conclusion, Kt/VDC and Kt/VQC should be considered as valid measures fordialysis efficiency. However, the limits of agreement between Kt/VQC and eKt/Vwere closer than Kt/VDC

Medición de la dosis de diálisis mediante diferentes módulos integrados en un mismo monitor / Measure of dialysis dose by different integrated modules within the same monitoring device

La recolección total del líquido de diálisis para cuantificar la cantidad total de urea eliminada durante la hemodiálisis (HD) se ha considerado la técnica «gold estándar» para medir la dosis de diálisis. Dada la dificultad de este método se han propuesto otros alternativos como el modelo cinético de la Urea (Kt/V), la medición de la dialisancia iónica o la recogida de muestras representativas del líquido de diálisis total. El objetivo de este trabajo es comparar la fiabilidad y concordancia de dos dispositivos de medida (dialisancia iónica y recogida parcial de líquido de diálisis) integrados en el mismo monitor de diálisis y compararlos con los propuestos por el modela cinético de la urea (MCU) para la medición de la dosis de diálisis (Kt/V) y otros parámetros de HD. Para ello se estudiaron 20 pacientes (16V/4M) con una edad media de 64,5 ± 13 años, estables en programa de HD y dializados con el monitor Integra® (Hospal) equipado con los biosensores Diascan (DC) y Quantiscan (QC). El volumen de distribución de urea (VD) se calculó a partir de la fórmula de Watson y por el QC. La generación de urea se calculó a partir del MCU y el Kt/V se determinó por la fórmula de Daurgidas 2ª generación corregida para el rebote (eKt/V), por el DC y el QC. La transferencia de masa de urea medida por QC fue de 37,2 ± 13,8 g. El VD por la fórmula de Watson y por QC fue de 35,7 ± 6,6 y de 35,06 ± 9,9 L respectivamente (ns) y mostraron una correlación significativa (r: 0,82 p < 0,001). Los valores de aclaramiento (K), mediante DC, y QC fueron similares KQC: 230,3 ± 56,5 ml/min, KDC: 214,05 ± 24,3 ml/min (ns) No se apreciaron diferencias en el Kt/V calculado por DC y el eKt/V (KtVDC: 1,64 ± 0,33 vs KtVeq; 1,61 ± 0,26). El coeficiente de correlación fue de r: 0,45 (p < 0,05). Por el contrario los valores de Kt/VQC fueron superiores a los calculados por el eKtV (1,67± 0,22 vs. 1,61 ± 0,26). El coeficiente de correlación fue de r: 0,94 ( p < 0,001). La generación de urea por el MCU fue de 8,7 ± 3,4 y por QC de 8,6 ± 3,2 g/ 24h (ns) r: 0,94 p < 0,001). Podemos concluir que tanto la medición de la dialisancia iónica mediante el DC, como la recogida de muestras representativas del líquido de diálisis mediante el QC, son métodos sencillos, fiables y reproducibles que nos permiten medir de manera rápida la eficacia dialítica y otros parámetros de hemodiálisis. En nuestra experiencia la cuantificación de la dosis de diálisis mediante el QC presenta una mayor concordancia que la realizada con DC

The «gold standard» method to measure the mass balance achieved during dialysis for a given solute is based on the total dialysate collection. This procedure is unfeasible and too cumbersome. For this reason, alternative methods have been proposed including the urea kinetic modelling (Kt/V), the measurement of effective ionic dialysance (Diascan), and the continuous spent sampling of dialysate (Quantiscan). The aim of this study was to compare the reliability and agreement of these two methods with the formulas proposed by the urea kinetic modelling for measuring the dialysis dose and others haemodialysis parameters. We studied 20 stable patients (16 men/4 women) dialyzed with a monitor equipped with the modules Diascan (DC) and Quantiscan (QC) (Integra®. Hospal). The urea distribution volume (VD) was determined using anthropometric data (Watson equation) and QC data. Kt/V value was calculated according to Daurgidas 2nd generation formula corrected for the rebound (eKt/V), and using DC (Kt/VDC) and QC (Kt/VQC) data. The total mass of urea removed was calculated as 37,93 ± 16 g/session. The VD calculated using Watson equation was 35.7 ± 6.6 and the VDQC was 35.06 ± 9.9. And they showed an significative correlation (r:0,82 p < 0.001). The (VDQCVDWatson) difference was –0.64 ± 5.8L (ns). Kt/VDC was equivalent to those of eKt/V (1.64 ± 0.33 and 1.61 ± 0.26, mean difference –0.02 ± 0.29). However, Kt/VQC value was higher than eKt/V (1.67 ± 0.22 and 1.61 ± 0.26 mean difference 0.06 ± 0.07 p < 0.01). Both values correlated highly (R2: 0.92 p < 0.001). Urea generation (G) calculated using UCM was 8.75 ± 3.4 g/24 h and those calculated using QC was 8.64 ± 3.21 g/24 h. Mean difference 0.10 ± 1.14 (ns). G calculated by UCM correlated highly with that derived from QC (R2: 0.88 p < 0.001). In conclusion, Kt/VDC and Kt/VQC should be considered as valid measures for dialysis efficiency. However, the limits of agreement between Kt/VQC and eKt/V were closer than Kt/VDC