Transfusion requirements during continuous veno-venous haemofiltration: – the importance of filter life

Objective: To investigate the relationship between loss of haemofilter circuits due to blood clots and requirement for blood transfusion in intensive care patients. Design: Retrospective case note review. Setting: A British, nine-bed, tertiary, medical and surgical intensive care unit (ICU) serving a 950-bed university teaching hospital. Patients: Thirty-three ICU patients requiring haemofiltration for more than 48 h. Thirty-three comparison patients requiring 7 or more days of intensive care, without haemofiltration. Methods: ICU, haemofiltration and haematology records were examined retrospectively. Note was taken of demographic data, daily haemoglobin concentrations and the dates and numbers of blood transfusions and haemofilter clots. Results: The study groups did not differ significantly in terms of age, sex and length of ICU stay. Haemofiltered patients had higher APACHE II scores (21 vs 15, p=0.006), lower haemoglobin concentrations (102 vs 110 g/l, p=0.0001) and higher blood transfusion rates (1.1 vs 0.3 units/day, p<0.0001) when compared to the non-haemofiltered group. There was a positive correlation between haemofilter blood clot rate and blood transfusion rate (r=0.48). More blood was transfused on days when haemofilter blood clots occurred than on days when no haemofilter clot occurred (1.0 vs 0.59 units, p=0.03). Conclusion: Haemofiltration is associated with an increased requirement for transfusion of blood. The temporal relationship between occurrence of haemofilter blood clots and transfusion of blood suggests that haemofilter lifespan may be an important determinant of this.