Feasibility of Near-Infrared Spectroscopy and Peripheral Arterial Disease Risk in CKD

Background: Peripheral arterial disease (PAD) is common in chronic kidney disease (CKD). The role of microvasculature (MV) in the development and progression of PAD is recognized. Near-infrared spectroscopy (NIRS) tests muscle oxygen utilization (mVO2) and reactive hyperemia (MV function) non-invasively but its role in CKD and PAD is unknown. We evaluated NIRS feasibility and compared parameters in severe CKD with healthy controls. We explored its reliability and correlation with a MV referent test, velocity time integral (VTI). Methods: A priori, feasibility was ≤10% of tests with i. discomfort and test termination ii. incomplete ischemic occlusion or iii. uninterpretable data. Participants completed baseline tests, Doppler US with reactive hyperemia from brachial and popliteal arteries for VTI and NIRS from the tibialis anterior muscle. An ischemic occlusion 50 mmHg above systolic BP for 5 minutes was used. The CKD group had repeat testing <14 days. Diagnostic accuracy testing was planned for NIRS and VTI correlations >0.7 and intraclass correlation coefficients (ICC) > 0.7. Results: 39 CKD 5/5D and 20 controls participated. CKD participants were older with higher median systolic BP 135 mmHg [125,150] vs 109 [102,118], ABI 1.12 [1.03,1.20] vs 1.02 [0.89,1.06] and TBI 0.82 [0.77,0.92] vs 0.98 [0.93,1.03]. In CKD, 9 tests (23%) were terminated due to discomfort from the ischemic provocation vs none in controls. In CKD, 20% of tests had incomplete occlusions vs 10% in controls and 13% were uninterpretable vs 0% in controls. In CKD, brachial artery peak VTI was 55.8 cm [42.7, 71.3] vs 82.8 cm [76.2,97.3] in controls (P<0.001). Popliteal peak VTI results were similar. Median mVO2 was higher in CKD: 0.25 %/second [0.23,0.28] vs 0.20 [0.18,0.24] (P=0.007) and reactive hyperemic response was lower in CKD oxyhemoglobin recovery slope 0.61 µM/sec [0.50,0.93] vs 0.93 [0.69,1.21] (P=0.007) (Figure). No NIRS tests had correlations >0.7 and ICCs >0.7. Conclusion: Ischemic provocation limited feasibility. mVO2 and reactive hyperemia from NIRS in CKD was consistent with muscle adaptations in PAD. Applications of NIRS in PAD should be evaluated in larger studies using alternative provocation tests.