A non-invasive approach to monitoring microcirculatory health before and after hemodialysis in renal patients using nailfold video capillaroscopy with optical reflectance analysis

Maintaining physiological blood pressure is a critical goal in the prevention of cardiovascular events, whereas tissue perfusion depends on the balance between systemic blood pressure and tissue microvascular resistance. The nailfold capillary is considered a window for directly assessing microvascular flow in the body. In this study, nailfold video capillaroscopy was used to determine the acute effects of hemodialysis on microvascular flow dynamics and optical reflectance in 11 patients with renal disease (ages 71 ± 14 years). The study aimed to determine if capillary morphology, flow dynamics, or optical reflectance are sensitive to hemodialysis-induced changes in blood composition. The capillary morphologies, flow speed distributions, and pixel intensity fluctuations before and after hemodialysis were compared via previously developed image analysis software. The correlations of the measured parameters with blood compositions were then examined. No consistent changes in measured capillary diameters, lengths, or flow speeds were observed with dialysis. In contrast, the temporal variations in optical reflectance were significantly altered after dialysis and were observed to be correlated with changes in inorganic phosphate concentrations. Finally, the capillary flow speed was found to be independent of the spatiotemporal variations in capillary diameter. In conclusion, dynamic changes in the optical reflectance represent acute changes in blood composition that are induced by hemodialysis. These findings underscore the potential of using non-invasive video capillaroscopy clinically to monitor microcirculatory health and manage cardiovascular risk in patients with renal disease.