Acute kidney injury is often treated with the use of continuous renal replacement therapy. Two commonly used treatments are continuous venvenous hemofiltration (CVVH)and continuous venovenous hemodialysis (CVVHD). CVVH uses convective clearance to remove toxins and solutes from the patients circulation, while CVVHD relies on diffusive clearance to remove these same toxins/solutes. This study will evaluate which of these two methods is more effective at clearing the body of waste/solutes.

We hypothesize that renal replacement therapy by either modality (hemodialysis or hemofiltration; CVVHD or CVVH, respectively) using a modern membrane and higher blood flow rates will be associated with similar clearances of both small and middle molecular weight solutes. We further believe that continuous renal replacement therapy using CVVHD will be associated with decreased clotting events and longer hemofilter survival, as well as improved resource utilization (i.e. nursing time, alarms, etc.).

Inclusion Criteria:

• Age 18 or older and able to sign consent (or surrogate).
• Must have been referred to the inpatient Nephrology consult service for evaluation of acute kidney injury (AKI).
• Expected survival of at least 48 hours.

Exclusion Criteria:

• Hemoglobin < 8 g/dl
• Serum potassium ≥6.5 milliequivalents per liter (mEq/L)
• Weight > 120kg.