How to understand real net ultrafiltration and its association with low blood pressure in critically ill patients with renal replacement therapy

The concept of net ultrafiltration (UF ) mentioned in the paper by Murugan et al. in a recent issue of Critical Care does not equate to the real UF in patients with renal replacement therapy initiation. Furthermore, the baseline blood pressure among the groups had a statistically significant difference. Both of these two factors may affect the final results. Thus, we should be cautious interpreting the conclusions.