Exploring a Predictive System for Intradialytic Hypotension Using Optical Blood Flow Monitoring

Background: Peripheral artery disease (PAD), especially lower extremity artery disease (LEAD) and chronic limb-threatening ischemia (CLTI), is highly prevalent in hemodialysis patients and is associated with poor prognosis including lower limb amputation and cardiovascular mortality. In particular, intradialytic hypotension (IDH) has been identified as an independent risk factor for PAD onset and progression. To investigate the dynamic changes in peripheral vascular resistance during hemodialysis using diffuse correlation spectroscopy (DCS), and to evaluate whether these changes are associated with dialysis blood pressure decline. Methods: We conducted a prospective observational study involving maintenance hemodialysis patients. Muscle blood flow in the anterior tibialis was continuously monitored using a bedside DCS system during a standard hemodialysis session. Blood pressure was measured every 30 to 60 minutes. Tissue perfusion depth was adjusted to ~1.5 cm by varying the distance between the light source and detector probes. Peripheral vascular resistance was calculated by dividing mean arterial pressure by muscle blood flow. Results: At the time of analysis with 13 patients, those with a significant decline in blood pressure by the end of dialysis (drop group, n = 5) showed a notable reduction in peripheral vascular resistance. A strong positive correlation (r = 0.83, p < 0.01) was observed between end-of-dialysis blood pressure and peripheral vascular resistance normalized to baseline. This relationship was preserved even when vascular resistance measured at 50% and 75% of dialysis duration was analyzed. These results suggest that impaired sympathetic vasoconstriction or autonomic dysregulation may lead to failure in maintaining vascular resistance, resulting in reduced venous return and blood pressure. Conclusion: Real-time monitoring of muscle blood flow using DCS revealed a close association between decreased peripheral vascular resistance and intradialytic blood pressure decline. Our findings highlight the utility of DCS in identifying hemodialysis patients at risk for hypotension by detecting early vascular response impairment.