How can you tell a dialyzer is clotting?

• A. Dark blood in dialyzer
• B. Air detector alarms
• C. Rising TMP
• D. Increased arterial pressure

Answer: (C)

Clotting inside the dialyzer raises resistance to blood flow across the membrane, which increases the pressure difference across it—transmembrane pressure (TMP). When clot forms, the fibers become blocked, so TMP climbs. Seeing a rising TMP during a dialysis run is the clearest sign that the dialyzer is starting to clot and may lose efficiency, often prompting stopping the run and replacing the dialyzer or adjusting anticoagulation. Other signs, like dark blood in the dialyzer, air detector alarms, or a higher arterial pressure, are not as specific to clotting and can result from other issues. So, a rising TMP is the best indicator of dialyzer clotting.