Rise in transmembrane pressure is most directly a sign of:

• A. Clotting in the circuit
• B. Venous needle infiltration
• C. Ultrafiltration rate too low
• D. Dialysate temperature changes

Answer: (A)

Transmembrane pressure (TMP) is the pressure difference driving fluid across the dialysis membrane; it reflects resistance on the blood side and across the membrane. When clotting occurs in the circuit or inside the dialyzer, resistance to blood flow increases. The machine must raise the pressure on the blood side to push plasma water through the membrane, so TMP rises. That direct rise points to clotting in the circuit as the likely cause.

Venous needle infiltration can cause alarms related to poor return flow but doesn’t directly increase the TMP across the membrane. If the ultrafiltration rate is too low, the gradient isn’t driven strongly, so TMP isn’t predictably higher. Dialysate temperature changes affect patient comfort and hemodynamics more than the pressure gradient across the membrane.