Department of Medical Biophysics, Western University, London, ON, Canada.
Centre for Critical Illness Research, Lawson Health Research Institute, London, ON, Canada.
J Clin Monit Comput. 2021 Dec;35(6):1453-1465. doi: 10.1007/s10877-020-00611-x. Epub 2020 Oct 26.
There is a need for bedside methods to monitor oxygen delivery in the microcirculation. Near-infrared spectroscopy commonly measures tissue oxygen saturation, but does not reflect the time-dependent variability of microvascular hemoglobin content (MHC) that attempts to match oxygen supply with demand. The objective of this study is to determine the feasibility of MHC monitoring in critically ill patients using high-resolution near-infrared spectroscopy to assess perfusion in the peripheral microcirculation.
Prospective observational cohort of 36 patients admitted within 48 h at a tertiary intensive care unit. Perfusion was measured on the quadriceps, biceps, and/or deltoid, using the temporal change in optical density at the isosbestic wavelength of hemoglobin (798 nm). Continuous wavelet transform was applied to the hemoglobin signal to delineate frequency ranges corresponding to physiological oscillations in the cardiovascular system.
31/36 patients had adequate signal quality for analysis, most commonly affected by motion artifacts. MHC signal demonstrates inter-subject heterogeneity in the cohort, indicated by different patterns of variability and frequency composition. Signal characteristics were concordant between muscle groups in the same patient, and correlated with systemic hemoglobin levels and oxygen saturation. Signal power was lower for patients receiving vasopressors, but not correlated with mean arterial pressure. Mechanical ventilation directly impacts MHC in peripheral tissue.
MHC can be measured continuously in the ICU with high-resolution near-infrared spectroscopy, and reflects the dynamic variability of hemoglobin distribution in the microcirculation. Results suggest this novel hemodynamic metric should be further evaluated for diagnosing microvascular dysfunction and monitoring peripheral perfusion.
需要床边方法来监测微循环中的氧输送。近红外光谱通常测量组织氧饱和度，但不能反映试图匹配氧供应与需求的微血管血红蛋白含量 (MHC) 的时变可变性。本研究的目的是使用高分辨率近红外光谱确定在危重病患者中监测 MHC 的可行性，以评估外周微循环的灌注。
对在三级重症监护病房入院 48 小时内的 36 例患者进行前瞻性观察队列研究。使用血红蛋白等吸光度波长（798nm）的光密度时间变化来测量股四头肌、肱二头肌和/或三角肌的灌注。连续小波变换应用于血红蛋白信号，以描绘与心血管系统生理振荡相对应的频率范围。
31/36 例患者具有足够的分析信号质量，最常见的是运动伪影的影响。MHC 信号在队列中表现出个体间的异质性，表现为变异性和频率组成的不同模式。同一患者的肌肉群之间的信号特征是一致的，并与全身血红蛋白水平和氧饱和度相关。接受血管加压药的患者信号功率较低，但与平均动脉压无关。机械通气直接影响外周组织中的 MHC。
高分辨率近红外光谱可连续测量 ICU 中的 MHC，并反映微循环中血红蛋白分布的动态可变性。结果表明，应进一步评估这种新的血流动力学指标，以诊断微血管功能障碍和监测外周灌注。
