Microcirculation plays an important role by supplying oxygen and nutrients to maintain our lives. It is known that, as pathogenesis of sepsis, the microcirculation is impaired at the early stage of sepsis. In this case, it is expected that thrombomodulin alfa (TM alfa) works for the recovery of microcirculation. Direct observation of the impairment and recovery of microcirculation related to sepsis may give us clear understanding of those phenomena. In this study, we conducted experiments to observe microcirculation of septic model rats with an optical system. In these experiments, by attaching a chamber to the back of each rat, the same region of the microcirculation was consecutively monitored. Then, these rats were divided into three groups: control model rats (sham group), septic model rats (diseased group), and septic model rats to which TM alfa was administered (treated group). Each group includes five rats. In the diseased group smaller vessels disappeared and larger vessels became thinner. On the other hand, the treated group showed at first the degradation of microcirculation then the recovery. This may indicate effectiveness of TM alfa. We also estimated the blood velocity and blood vessel diameter from the acquired motion pictures to evaluate condition of the microcirculation. As a result, we quantitatively confirmed while blood velocity and blood vessel diameter of the diseased group decreased, that of the treated group decreased and then recovered. It should be noted that the set of motion pictures obtained in these experiments has potentially useful information for further analysis and is to be open to relevant researchers.
Microcirculation plays an important role in maintaining our lives. Observing the microcirculation has been considered important in understanding the disease mechanisms and diagnosing diseases. Sidestream dark-field (SDF) imaging is one of the methods to observe the microcirculation. However, the SDF imaging has several problems for instance artifacts caused by pressure and heat. Measurement points is under pressure because SDF imaging requires direct contact with measurement points, which may affect hemodynamics. Therefore, we construct a non-contact setup. Furthermore, at the early stage of sepsis, it is known that the microcirculation is impaired. To investigate the relationship between the flow of red blood cells (RBCs) and septic shock, we conducted an experiment using the setup to observe septic model rats and sham rats. Moreover, we calculated the blood velocity to estimate the flow of RBCs by using acquired motion pictures. We confirmed that the sham rats showed slight change in lactate value during the observation and improved the blood velocity compared with just after abdominal closure. However, lactate value of the septic model rats increased and the blood velocity of septic model rats decreased. This finding suggests that microcirculatory alteration may be a sign of sepsis and septic shock progression.
Monitoring oxygen saturation (SO2) in microcirculation is effective for understanding disease dynamics. We have developed an SO2 estimation method, sidestream dark-field (SDF) oximetry, based on SDF imaging. SDF imaging is a noninvasive and clinically applicable technique to observe microcirculation. We report the first in vivo experiment observing the changes in SO2 of microcirculation using SDF oximetry. First, heat from the light-emitting diodes used for the SDF imaging might affect hemodynamics in microcirculation, hence, we performed an experiment to evaluate the influence of that on the SDF oximetry. The result suggested that SDF oximetry had enough stability for long-term experiments. Then, to evaluate the sensitivity of SDF oximetry to alterations in the hemodynamics of the microcirculation, we observed the time-lapsed SO2 changes in the dermis microcirculation of rats under hypoxic stimulation. We confirmed that the SO2 estimated by SDF oximetry was in accordance with changes in the fraction of inspired oxygen (FiO2). Thus, SDF oximetry is considered to be able to observe SO2 changes that occur in accordance with alteration of the microcirculation.
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