Prevention of Intradialytic Hypotension with Intermittent Back-Filtrate Infusion Haemodiafiltration: Insights into the Underlying Mechanism

BACKGROUND: Intradialytic hypotension (IDH) is a major challenge to safely performing haemodialysis. Blood volume depletion due to fluid removal is a major cause of hypotension, so more emphasis should be placed on finding alternative modalities to traditional constant rate ultrafiltration. SUMMARY: Intermittent back-filtrate infusion haemodiafiltration (I-HDF) utilises purified online quality dialysate with an automated dialysis machine. A bolus of 200 mL of dialysate is repetitively infused at 30-min intervals. A pilot study with 68 hypotension-prone patients revealed that I-HDF can reduce the frequency of IDH interventions, particularly in elderly patients and patients with large interdialytic weight gain (IDWG). This was typically accompanied by an increase in intradialytic blood pressure and decreased tachycardia in the latter half of the session, suggesting reduced sympathetic stimulation during I-HDF. Protective mechanisms involved in the pathophysiology of IDH could be explained in part by the findings obtained in this pilot study. Intermittent increases in blood pressure during I-HDF may prevent venous pooling (i.e., the DeJager-Krogh phenomenon), and reduced sympathetic stimulation may maintain a physiological state less likely to induce the cardio-vagal reflex (i.e., the Bezold-Jarisch reflex). The plasma refilling rate (PRR), evaluated as the refilling fraction (RF), is unexpectedly smaller in I-HDF. However, in patients who respond, the RF is well achieved, which suggests that adequate PRR is the central physiology for preventing IDH. Patients for whom I-HDF is effective are characteristically relatively elderly and show increased IDWG. Blood pressure increment and reduced sympathetic activation in I-HDF may be a mechanism for prevention of IDH. Key Messages: Evaluating relative changes in blood volume during I-HDF will provide a new perspective for exploring appropriate ultrafiltration modification that circumvents IDH.