Low Blood Flow Continuous Veno-Venous Haemodialysis Compared with Higher Blood Flow Continuous Veno-Venous Haemodiafiltration: Effect on Alarm Rates, Filter Life, and Azotaemic Control

Title: Low blood flow continuous veno-venous haemodialysis (CVVHD) compared with higher blood flow continuous veno-venous haemodiafiltration (CVVHDF): effect on alarm rates, filter life, and azotaemic control. Introduction: Continuous renal replacement therapy (CRRT) can be delivered via convective, diffusive, or mixed approaches. Higher blood flows have been advocated for convective clearance efficiency and promotion of filter life. It is unclear whether a lower blood flow predominantly diffusive approach may benefit filter life and alarm rates. Materials and Methods: Sequential cohort study of 284 patients undergoing 874 CRRT circuits from January 2015 to August 2018 in a single university-associated tertiary referral hospital in Australia. Patients underwent a protocol of either CVVHDF at blood flow 200-250 mL/min or CVVHD at blood flow 100-130 mL/min. Machine and patient data were analysed. Outcomes of azotaemic control, filter life, and warning alarm rates were log transformed and analysed with mixed linear modelling with patient as a random effect. Results: Both groups had similar azotaemic control (effect estimate on log creatinine CVVHD vs. CVVHDF 1.04 [0.87-1.25], p = 0.68) and median filter life (CVVHDF 16.8 [8.4-90.5] h and CVVHD 16.4 [9.4-82.3] h, p = 0.97). However, circuit pressures were less extreme with a narrower distribution during CVVHD. Multivariate analysis showed CVVHD had a reduced risk of warning alarms (incidence risk ratio [IRR] 0.51 [0.38-0.70]) and femoral access placement also had a reduced risk of alarms (IRR 0.55 [0.41-0.73]). Conclusion: Low blood flow CVVHD and femoral vascular access reduce alarms while maintaining azotaemic control and circuit patency thus minimizing bedside clinician workload.