Safety and survival benefit of very high extracorporeal flow (Qb of 600 mL/min).

Abstract

Introduction: High-volume convective online hemodiafiltration (HDF-OL) (>24 liters) is considered the gold standard for optimizing the clearance of medium- and large-molecular-weight solutes in end-stage renal disease. Beyond this, there do not appear to be substantial improvements in survival outcomes. However, it is often assumed that extracorporeal blood flow (Qb)—which is the primary determinant of Kt/V—should remain below the convective volume, even though the latter can be optimized. Questions have traditionally been raised regarding whether prescribing extracorporeal flows of 500–600 mL/min via large-bore vascular access compromises the safety or long-term viability of the technique.

Materials and Methods: A retrospective observational study was conducted using the institutional database. The study compared a historical group of patients undergoing high-volume HDF-OL (>22 liters/session; 2019–2023) with a prescribed optimal extracorporeal flow of 450–480 mL/min against adult patients undergoing HDF-OL (>22 liters) who transitioned to a high extracorporeal flow program (Qb = 600 mL/min) using an arteriovenous fistula. To achieve the target Qb of 600 mL/min, the flow rate was increased by 25 mL/min per treatment until the patient tolerated 600 mL/min by the end of six consecutive thrice-weekly sessions. Shear stress observed during the Qb escalation period was monitored. If shear stress occurred, the management strategy involved reducing the flow to 470 mL/min, administering intravenous analgesia (1 g paracetamol), pausing the progressive Qb increase, performing upper-limb exercises with weights and a tourniquet, and attempting the progressive increase again one week later. A survival analysis was performed.

Results: There were 58 cases in group 1 and 50 in group 2. No differences were found regarding age, sex, percentage of diabetic patients, weight, or body mass index (Table 1). Survival was higher in the group with the higher extracorporeal flow, with a benefit of 37 months.

Conclusions: Optimizing extracorporeal blood flow to very high levels (Qb approx. 600 mL/min) via a progressive increase in patients with an arteriovenous fistula undergoing high-volume online hemodiafiltration (HDF-OL) is a viable, safe strategy with an outstanding clinical impact. Far from compromising vascular access stability, this guided adaptation protocol was associated with a significant increase in patient survival (yielding a net benefit of 37 months compared to conventional optimal flow). These findings suggest a need to rethink traditional limits on extracorporeal blood flow, positioning very high Qb as a key therapeutic pillar for maximizing clinical outcomes in end-stage renal disease.