Haemolysis associated with continuous venovenous renal replacement circuits

Extracorporeal circuits can cause haemolysis resulting in an increase in plasma-free haemoglobin (PFHb). High pressures and clots within the circuit have been identified as factors increasing the likelihood of haemolysis. Continuous venovenous haemodiafiltration (CVVHD) is associated with high circuit pressures as the pump-driven circuit clots over a period of time. PFHb was measured during CVVHD to determine if circuit life, maximum circuit pressure or the clotting of the haemofilter was associated with evidence of haemolysis. Circuit life up to 50 hours, circuit pressures or haemofilter clotting had no significant effect on PFHb. There was a small rise in PFHb in the circuits lasting beyond 50 hours. CVVHD circuits can be run up to 50 hours without concern for haemolysis.