Continuous renal replacement therapy with an automated monitor is superior to a free-flow system during extracorporeal life support

Abstract

Objectives: To determine whether integrated continuous renal replacement therapy provides more accurate fluid management than IV pump free-flow ultrafiltration in pediatric patients on extracorporeal life support.

Design: Retrospective study.

Setting: PICU and neonatal ICU in a tertiary academic center.

Patients: Infants and children less than 18 years old.

Interventions: Extracorporeal membrane oxygenation and continuous renal replacement therapy.

Measurements and main results: Clinical data collected on patients who received free-flow or integrated renal replacement therapy while on extracorporeal life support. Normalized ultrafiltration error was calculated as: (physician specified fluid loss per 24-hr period - actual fluid loss per 24-hr period) divided by patient body weight (kg). Mixed linear regression analyses were used to model longitudinal ultrafiltration error trajectories within each mode of ultrafiltration. Based on an analysis of 458 serial ultrafiltration fluid balance measurements, integrated ultrafiltration was significantly more accurate than free-flow ultrafiltration (normalized ultrafiltration error of 1.2 vs 13.1 mL; p < 0.001). After adjusting for patient factors and time, integrated ultrafiltration was associated with a significantly lower normalized ultrafiltration error (variable estimate, -24 ± 6; p < 0.001). The use of integrated ultrafiltration was associated with shorter duration of extracorporeal life support (384 vs 583 hr, p < 0.001) and renal replacement therapy (185 vs 477 hr, p < 0.001) than free-flow patients. Overall ICU and hospital length of stay and in-hospital mortality were similar between the groups.

Conclusions: While free-flow ultrafiltration has the advantages of simplicity and low cost, integrated renal replacement therapy provides more accurate fluid management during extracorporeal life support. Better fluid status management with integrated renal replacement therapy may contribute to shorter duration of extracorporeal life support.