The purpose of this observational study is to measure the number of calories delivered from fluids used in continuous renal replacement therapy (CRRT). We are doing this research study because the fluids used in this treatment may deliver an important number of calories. In the future this could help better estimate how much nutrition patients in the Critical Care Unit should get every day from other sources like tube feeding or nutrition through a person's veins.

The goal of this study is to quantify the specific metabolic contribution of standard continuous renal replacement protocols (including citrate anticoagulation) in the intensive care unit patient population at Mayo Clinic in Rochester, Minnesota utilizing a prospective, observational study. This data will allow practitioners to better tailor caloric provision with nutrition support programs, minimizing the risk of overfeeding in this complex critical care patient population.

Inclusion Criteria:

• Age greater than or equal to 18 years
• Patients in an intensive care unit anticipated to receive greater than or equal to 24 hours of continuous venovenous hemofiltration.
• Receiving regional citrate anticoagulation with ACD-A solution.

Exclusion Criteria:

• Vulnerable adults
• Pregnant
• BMI > 40
• Patient on extracorporeal membrane oxygenation therapy
• Reversal of port connections on the dialysis catheter and dialysis circuit lines

Critically ill patients initiated on continuous venovenous hemofiltration receiving regional citrate anticoagulation with ACD-A solution.