Validation of the inverse method for the determination of the access flow with thermodilution.

INTRODUCTION: Thermodiluction is a widely used method for measuring vascular access flow (QA). Among the possibilities of TD, the reverse method (MI) can be beneficial in the execution time, without impact on the dialysis efficacy (Kt). However, it is not a sufficiently studied technique. METHOD: Transversal study of 117 arteriovenous fistulas (AVF). Two QA measurements were taken with the method described by the manufacturer (MR) and another with MI. MI is bases in the obtention of an inverted recirculation registry at the beginning of the session and a single subsequent recirculation measurement with the lines in normal position. In the concordance analysis, the Bland-Altman method and Cohen's Kappa index were used. RESULTS: Very good concordance between MR and MI was evidenced for QA below 700 ml/min, but it worsens as flow increases. The median variability between the MR measurements (intra-method variability) was 3.4% (-17.13). This value did not differ from the median variability generated between MR and MI (inter-method variability), which was 2% (-14, 12) (P = 0.287). The degree of agreement between the two to identify AVFs susceptible to intervention was very good (K = 0.834). The time spent using the MI was significantly shorter (P = 0.000) without evidence of variations in the Kt of the measurement sessions (P = 0.201). CONCLUSIONS: The thermodiluction MI is valid to determine the flow of the vascular access, especially in Qa lower than 700 ml/min, with great time savings, simplification of the procedure and without modifying the dialysis efficiency. The variability between the measurement by MR and MI is similar to that of MR. The concordance between methods in identifying potentially pathological AVFs is very good.

Validación del método inverso para la determinación del flujo de acceso con termodilución / Validation of the inverse method for the determination of the access flow with thermodilution

Introducción: La termodilución es un método ampliamente usado para la medición del flujo de acceso vascular (QA). Entre las posibilidades de la termodilución, el método inverso (MI) puede ser beneficioso en el tiempo de ejecución, sin repercusión en la eficacia dialítica (Kt). Sin embargo, no es una técnica lo suficientemente estudiada.MétodoEstudio transversal sobre 117 fístulas arteriovenosas. Se realizaron 2 mediciones de QA con el método descrito por el fabricante (MR) y otra con MI. El MI se basa en la obtención del registro de recirculación invertida al iniciar la sesión y una única medición posterior de recirculación con las líneas en posición normal. En el análisis de concordancia se utilizó el método Bland-Altman y el índice kappa de Cohen.ResultadosSe evidenció muy buena concordancia entre MR y MI para QA inferiores a 700ml/min, pero empeora a medida que aumenta el flujo. La variabilidad mediana entre las mediciones con MR (variabilidad intramétodo) fue del 3,4% (−17,13). Este valor no difirió de la variabilidad mediana generada entre MR y MI (variabilidad intermétodo), que fue del 2% (−14,12) (p=0,287). El grado de acuerdo entre ambos para identificar fístulas arteriovenosas susceptibles de intervención fue muy bueno (kappa=0,834). El tiempo empleado utilizando el MI fue significativamente menor (p=0,000), sin evidenciarse variaciones en el Kt de las sesiones de medida (p=0,201).ConclusionesEl MI de termodilución es válido para determinar el flujo del acceso vascular, especialmente en QA inferiores a 700ml/min, con gran ahorro de tiempo, simplificación del procedimiento y sin modificar la eficacia de diálisis. La variabilidad entre la medición por MR y MI es similar a la propia del MR. La concordancia entre métodos a la hora de identificar fístulas arteriovenosas potencialmente patológicas es muy buena. (AU)

Introduction: Thermodilution is a widely used method for measuring vascular access flow (QA). Among the possibilities of thermodilution, the reverse method (RM) can be beneficial in the execution time, without impact on the dialysis efficacy (Kt). However, it is not a sufficiently studied technique.MethodTransversal study of 117 arteriovenous fistulas. Two QA measurements were taken with the method described by the manufacturer (MR) and another with RM. RM is based on the obtention of an inverted recirculation registry at the beginning of the session and a single subsequent recirculation measurement with the lines in normal position. In the concordance analysis, the Bland-Altman method and Cohen's Kappa index were used.ResultsVery good concordance between MR and RM was evidenced for QA below 700ml/min, but it worsens as flow increases. The median variability between the MR measurements (intra-method variability) was 3.4% (−17.13). This value did not differ from the median variability generated between MR and RM (inter-method variability), which was 2% (−14,12) (P=.287). The degree of agreement between the 2 to identify arteriovenous fistulas susceptible to intervention was very good (Kappa=0.834). The time spent using the RM was significantly shorter (P=.000) without evidence of variations in the Kt of the measurement sessions (P=.201).ConclusionsThe thermodilution RM is valid to determine the flow of the vascular access, especially in QA lower than 700ml/min, with great time savings, simplification of the procedure and without modifying the dialysis efficiency. The variability between the measurement by MR and RM is similar to that of MR. The concordance between methods in identifying potentially pathological arteriovenous fistulas is very good. (AU)

Validation of the inverse method for the determination of the access flow with thermodilution. / Validación del método inverso para la determinación del flujo de acceso con termodilución.

INTRODUCTION: Thermodilution is a widely used method for measuring vascular access flow (QA). Among the possibilities of thermodilution, the reverse method (RM) can be beneficial in the execution time, without impact on the dialysis efficacy (Kt). However, it is not a sufficiently studied technique. METHOD: Transversal study of 117 arteriovenous fistulas. Two QA measurements were taken with the method described by the manufacturer (MR) and another with RM. RM is based on the obtention of an inverted recirculation registry at the beginning of the session and a single subsequent recirculation measurement with the lines in normal position. In the concordance analysis, the Bland-Altman method and Cohen's Kappa index were used. RESULTS: Very good concordance between MR and RM was evidenced for QA below 700ml/min, but it worsens as flow increases. The median variability between the MR measurements (intra-method variability) was 3.4% (-17.13). This value did not differ from the median variability generated between MR and RM (inter-method variability), which was 2% (-14,12) (P=.287). The degree of agreement between the 2 to identify arteriovenous fistulas susceptible to intervention was very good (Kappa=0.834). The time spent using the RM was significantly shorter (P=.000) without evidence of variations in the Kt of the measurement sessions (P=.201). CONCLUSIONS: The thermodilution RM is valid to determine the flow of the vascular access, especially in QA lower than 700ml/min, with great time savings, simplification of the procedure and without modifying the dialysis efficiency. The variability between the measurement by MR and RM is similar to that of MR. The concordance between methods in identifying potentially pathological arteriovenous fistulas is very good.