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

Purpose: To discuss the techniques currently available to evaluate the microcirculation in crit- ically ill patients. In addition, the most clinically relevant microcircu- latory alterations will be discussed. Methods: Review of the literature on methods used to evaluate the microcirculation in humans and on microcirculatory alterations in criti- cally 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 heter- ogeneity of microcirculatory perfusion, with non-perfused capil- laries in close vicinity to perfused capillaries. Techniques used to eval- uate the microcirculation in humans should take into account the hetero- geneity 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 sublin- gual microcirculation. Laser Doppler and tissue O2 measurements