Circuit Life Versus Bleeding Risk: The Impact of Achieved Activated Partial Thromboplastin Time Versus Achieved Filtration Fraction

Abstract

Whilst prolonging hemofilter (circuit) life, heparin increases bleeding risk. The impact of achieved activated partial thromboplastin time (APTT) on circuit life and bleeding risk has not been assessed in a modern critically ill cohort. Lowering filtration fraction may be an alternative means of prolonging circuit life, but is often overlooked in critical care. An observational study of 309 consecutive circuits in a general intensive care unit was conducted using a wide target APTT range. Multilevel modeling was used to predict circuit life and bleeding according to achieved APTT and filtration fraction. Independent predictors of circuit failure (i.e. unplanned ending of treatment) included filtration fraction (P<0.001, HR 1.07 per 1% increase), peak APTT (P<0.001, HR 0.8 per 10 s increase or 0.3 APTR increase) and baseline PT (P=0.014, HR 0.91 for every 50% increase). The only significant predictor of bleeding was peak APTT (P=0.017, OR 1.05 per 10 s increase). Every 10 s APTT increase was associated with a 20% reduction in circuit failure, but a 5% increase in hemorrhage. A 3% reduction in filtration fraction was associated with the same improvement in circuit life as a 10 s increase in APTT. Increasing APTT prolongs circuit life but carries a substantial risk of bleeding even in modern practice. Filtration fraction has a large impact on circuit life in the critically ill: a 3% reduction in filtration fraction, e.g. by increasing blood flow or delivering some of the clearance via dialysis, would be expected to reduce circuit failure as much as a 10 s increase in APTT.

Development and External Validation of a Model for Predicting Sufficient Filter Lifespan in Anticoagulation-Free Continuous Renal Replacement Therapy Patients

“…Fealy et al [26] reported in a randomized controlled trial that longer APTT and decreased PLT count were independently associated a reduced likelihood of circuit clotting. The similar association of APTT [32] and PLT count [33,34] with CRRT filter lifespan were reported in observational studies as well. Zhang et al [35] reported that lower pH was significantly associated with longer filter lifespan in a multivariable Cox regression model.…”

A Prediction Model of Sufficient Filter Lifespan in Anticoagulation-free CRRT&nbsp;Patients

“…Fealy, N.et al [25] found in a randomized controlled trial (RCT) that longer APTT (hazards ratio [HR] 0.98, P = 0.002) and decreased platelet count (HR 1.19, P = 0.03) were independently associated with a reduced likelihood of circuit clotting. The similar association of APTT [31] and platelet count [32,33] with CRRT lter lifespan were reported in observational studies as well. Zhang Z et al [34] reported that lower pH was signi cantly associated with longer lter lifespan in a multivariable Cox regression model.…”

Revisiting Filtration Fraction as an Index of the Risk of Hemofilter Clotting in Continuous Venovenous Hemofiltration

“…Where Q UF-net is fluid removal rate, Q RF-post is postfilter fluid replacement rate, and Q B is blood flow rate. For the calculation of filtration fraction when replacement fluid is administered prefilter, most experts propose adding the prefilter replacement fluid rate (Q RF-pre ) to both numerator and denominator, as in Equation 2 (3,4):…”