Continuous real-time monitoring of the adequacy of cerebral perfusion can provide important therapeutic information in a variety of clinical settings. The current clinical availability of several non-invasive near-infrared spectroscopy (NIRS)-based cerebral oximetry devices represents a potentially important development for the detection of cerebral ischaemia. In addition, a number of preliminary studies have reported on the application of cerebral oximetry sensors to other tissue beds including splanchnic, renal, and spinal cord. This review provides a synopsis of the mode of operation, current limitations and confounders, clinical applications, and potential future uses of such NIRS devices.

Near-infrared spectroscopy as an index of brain and tissue oxygenation

CARDIOVASCULAR Near-infrared spectroscopy as an index of brain and tissue oxygenation

Conventional cardiovascular monitoring may not detect tissue hypoxia, and conventional cardiovascular support aiming at global hemodynamics may not restore tissue oxygenation. NIRS offers non-invasive online monitoring of tissue oxygenation in a wide range of clinical scenarios. NIRS monitoring is commonly used to measure cerebral oxygenation (rSO(2)), e.g. during cardiac surgery. In this review, we will show that tissue hypoxia occurs frequently in the perioperative setting, particularly in cardiac surgery. Therefore, measuring and obtaining adequate tissue oxygenation may prevent (postoperative) complications and may thus be cost-effective. NIRS monitoring may also be used to detect tissue hypoxia in (prehospital) emergency settings, where it has prognostic significance and enables monitoring of therapeutic interventions, particularly in patients with trauma. However, optimal therapeutic agents and strategies for augmenting tissue oxygenation have yet to be determined.

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Monitoring tissue oxygenation by near infrared spectroscopy (NIRS): background and current applications

Purpose: To discuss the techniques currently available to evaluate the microcirculation in critically ill patients. In addition, the most clinically relevant microcirculatory alterations will be discussed. Methods: Review of the literature on methods used to evaluate the microcirculation in humans and on microcirculatory alterations in critically ill patients. Results: In experimental conditions, shock states have been shown to be associated with a decrease in perfused capillary density and an increase in the heterogeneity of microcirculatory perfusion, with non-perfused capillaries in close vicinity to perfused capillaries. Techniques used to evaluate the microcirculation in humans should take into account the heterogeneity of microvascular perfusion. Microvideoscopic techniques, such as orthogonal polarization spectral (OPS) and sidestream dark field (SDF) imaging, directly evaluate microvascular networks covered by a thin epithelium, such as the sublingual microcirculation. Laser Doppler and tissue O2 measurements satisfactorily detect global decreases in tissue perfusion but not heterogeneity of microvascular perfusion. These techniques, and in particular laser Doppler and near-infrared spectroscopy, may help to evaluate the dynamic response of the microcirculation to a stress test. In patients with severe sepsis and septic shock, the microcirculation is characterized by a decrease in capillary density and in the proportion of perfused capillaries, together with a blunted response to a vascular occlusion test. Conclusions: The microcirculation in humans can be evaluated directly by videomicroscopy (OPS/SDF) or indirectly by vascular occlusion tests. Of note, direct videomicroscopic visualization evaluates the actual state of the microcirculation, whereas the vascular occlusion test evaluates microvascular reserve.

Monitoring the microcirculation in the critically ill patient: current methods and future approaches.

Background:Currently, specific triage criteria, such as blood pressure, respiratory status, Glasgow Coma Scale, and mechanism of injury are used to categorize trauma patients and prioritize emergency department (ED) and trauma team responses. It has been demonstrated in previous literature that an a

https://www.kumc.edu/Documents/emergencydepartment/publications/Cannon_utility%20of%20shock%20in%20predicting%20mortality%20in%20trauma.pdf

Utility of the shock index in predicting mortality in traumatically injured patients.

Background:Near-infrared spectroscopy (NIRS) can continuously and noninvasively monitor tissue oxygen saturation (StO2) in muscle and may be an indicator of shock severity. Our purpose was to evaluate how well StO2 predicted outcome in high-risk torso trauma patients presenting in shock.Methods:The

Tissue oxygen saturation predicts the development of organ dysfunction during traumatic shock resuscitation

A simple continuous wave near-infrared algorithm for estimating local hemoglobin oxygen saturation in tissue (%StO2) is described using single depth attenuation measurements at 680, 720, 760, and 800 nm. Second derivative spectroscopy was used to reduce light scattering effects, chromophores with constant absorption, baseline/instrumentation drift, and movement artifacts. Unlike previous second derivative methods which focused primarily on measuring deoxyhemoglobin concentration; a wide 40 nm wavelength gap used for calculating second derivative attenuation significantly improved sensitivity to oxyhemoglobin absorption. Scaled second derivative attenuation at 720 nm was correlated to in vitro hemoglobin oxygen saturation to generate a %StO2 calibration curve. The calibration curve was insensitive to total hemoglobin, optical path length, and optical scattering. Measurement error due to normal levels of carboxyhemoglobin, methemoglobin, and water absorption were less than 10 %StO2 units. Severe methemoglobinemia or edema combined with low blood volume could cause StO2 errors to exceed 10 StO2 units. Both a broadband and commercial four-wavelength spectrometer (InSpectraTM) measured %StO2. The InSpectra tissue spectrometer readily detected limb ischemia on 26 human volunteers for hand, forearm, and leg muscles. A strong linear correlation, r2>0.93, between StO2 and microvascular %SO2 was observed for isolated animal hind limb, kidney, and heart.

https://www.spiedigitallibrary.org/journals/Journal-of-Biomedical-Optics/volume-10/issue-03/034017/Noninvasive-method-for-measuring-local-hemoglobin-oxygen-saturation-in-tissue/10.1117/1.1925250.pdf

Noninvasive method for measuring local hemoglobin oxygen saturation in tissue using wide gap second derivative near-infrared spectroscopy.

We describe a four wavelength continuous wave near-infrared algorithm for estimating hemoglobin oxygen saturation in tissue using single depth attenuation measurements. The 40 nm gap second derivative algorithm and in vitro calibration method provided StO2 measurements of reasonable accuracy that were applied across a variety of tissues and probe spacings with no measured or assumed values for optical pathlength or optical scattering.

Le Ann D. Anderson

Papers

Tissue oxygen saturation predicts the development of organ dysfunction during traumatic shock resuscitation

Noninvasive method for measuring local hemoglobin oxygen saturation in tissue using wide gap second derivative near-infrared spectroscopy.

A wide gap second derivative NIR spectroscopic method for measuring tissue hemoglobin oxygen saturation.