Continuous veno-venous hemodialysis (CVVHD)—CVVHD is similar to hemodialysis as described earlier but is continuous rather than episodic. This modality consists primarily of diffusive clearance of small molecules. Some convective clearance occurs, but to a lesser extent than diffusive clearance.

Continuous veno-venous hemodiafiltration (CVVHDF)—CVVHDF combines both CVVHD and CVVH. In this modality, a replacement solution infuses into the blood either prefiltration or postfiltration. At the same time, a dialysate solution runs countercurrent to the blood in the filter cartridge. This modality removes both small and medium-sized molecules from the blood. Studies are currently being performed to compare the relative advantages of and indications for CVVH, CVVHD, and CVVHDF.