Abstract The concept of net ultrafiltration (UFNET) mentioned in the Ash Catcher paper by Murugan et al.in a recent issue of Critical Care does not equate to the real UFNET in patients Buckle 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.