Variabilidad intramétodo en medidas del flujo del acceso vascular con termodilución: ¿Un enemigo en los programas de seguimiento?

Objective: To analyze the impact of the intra-method variability of thermodilution (TD) in the prospective measurements of the access flow (QA) and the relationship with the first-generation monitoring parameters. Method: Prospective study. Two consecutive QA measurements (M1 and M2) and a 6-month follow-up (M3) were performed. Demographic data and first-generation follow-up parameters were collected. Result: 112 arteriovenous fistulas (AVF) were analyzed. The median variability generated between M1 and M2 does not differ from the percentage of QA variation at 6 months (p=0.123). In 16.8% (14) of the patients the QA has decreased by more than 25% and in 28.9% (24) it increased by more than 25%. A slight tendency to increase the percentage of decrease in QA when the fistula flow was higher was evidenced (r=-0.229; p=0.006). On the other hand, a decrease in QA greater than 25% was not associated with a lower dose of dialysis (p=0.183), nor did it have a significant increase in dynamic venous pressure (p=0.823) or an increase in incidences during puncture (p=0.823). Conclusions: The presence of patients with an increase in flow greater than the intra-method variability, and the non-association between a decrease greater than 25% and changes in other follow-up parameters, raises suspicions about the presence of QA measurement errors. In relation to this, the combined use with first-generation methods is convenient, both to establish the baseline QA and to interpret the decreases in follow-up.