Background <p>Kidney replacement therapy (KRT) is frequently implemented in the intensive care unit. While measuring energy expenditure is recommended in the critically ill, the influence of KRT on indirect calorimetry (IC) is not fully clear. This prospective study aimed to investigate the influence of continuous veno-venous hemodialysis (CVVHD) and slow extended daily dialysis (SLEDD) on IC variables.</p> Patients and methods <p>We included critically ill mechanically ventilated adult medical patients on KRT for acute kidney injury. CVVHD was run with regional citrate anticoagulation, while SLEDD with systemic heparin anticoagulation. We conducted IC twice on every patient, either immediately before the planned termination of KRT and then an hour after the end of KRT or immediately before commencement of KRT and then again after an hour on KRT.</p> Results <p>We included 100 patients (75 males) with a median age of 64.0 years, a mean APACHE-II score of 30.9 and a mean SOFA score of 11.3 on the day of IC. There was no significant difference in median resting energy expenditure with versus without CVVHD (8029 [6993–9644] versus 7814 [6962–9304] kJ, <i>p</i> = 0.75) as well as with versus without SLEDD (9258 [8017–10,364] versus 9269 [8070–11,065] kJ, <i>p</i> = 0.63). The difference in resting energy expenditure between the two measurements was also not significant regardless of the sequence of IC measurements (<i>p</i> = 0.69).</p> Conclusion <p>This prospective study on critically ill adult patients did not show any significant difference for indirect calorimetry variables between measurements conducted during CVVHD and SLEDD compared to those without KRT. ClinicalTrials.gov ID: NCT04599569</p>