RESUMO
BACKGROUND: The study aims to investigate an optimal indicator for changing the filter during the continuous renal replacement therapy (CRRT) in intensive care unit (ICU) patients with acute kidney injury (AKI). METHODS: Patients with AKI requiring CRRT in an ICU were randomly divided into two groups for crossover trial, i.e., groups A and B. Patients in the group A were firstly treated with continuous veno-venous hemofiltration (CVVH), followed by continuous veno-venous hemodiafiltration (CVVHDF). Patients in the group B were firstly treated with CVVHDF followed by CVVH. Delivered doses of solutes with different molecular weights at the indicated time points between groups were compared. A correlation analysis between the delivered dose and pre-filter pressure (PPRE) and transmembrane pressure (PTM) was performed. Receiver operating characteristic (ROC) curves were constructed to evaluate the accuracy of PTM as an indicator for filter replacement. RESULTS: A total of 50 cases were analyzed, 27 in the group A and 23 in the group B. Delivered doses of different molecular-weight solutes significantly decreased before changing the filter in both modalities, compared with those at the initiation of treatment (all P<0.05). In the late stage of CRRT, the possible rebound of serum medium-molecular-weight solute concentration was observed. PTM was negatively correlated with the delivered dose of medium-molecular-weight solute in both modalities. The threshold for predicting the rebound of serum concentration of medium-molecular-weight solute by PTM was 146.5 mmHg (1 mmHg=0.133 kPa). CONCLUSIONS: The filter can be used as long as possible within the manufacturer's safe use time limits to remove small-molecular-weight solutes. PTM of 146.5 mmHg may be an optimal indicator for changing the filter in CRRT therapies to remove medium-molecular-weight solutes.