Is microcirculatory assessment ready for regular use in clinical practice?

Abstract

The present review discusses the current role of microcirculatory assessment in the hemodynamic monitoring of critically ill patients. Videomicroscopic techniques have demonstrated that microvascular perfusion is altered in critically ill patients, and especially in sepsis. These alterations are associated with organ dysfunction and poor outcome. Handheld microscopes can easily be applied on the sublingual area of critically ill patients. Among the specific limitations of these techniques, the most important is that these can mostly investigate the sublingual microcirculation. The representativity of the sublingual area may be questioned, especially as some areas may sometimes be more affected than the sublingual area. Also, evaluation of the sublingual area may be difficult in nonintubated hypoxemic patients. Alternative techniques include vasoreactivity tests using either transient occlusion or performing a thermal challenge. These techniques evaluate the maximal dilatory properties of the microcirculation but do not really evaluate the actual microvascular perfusion. Focusing on the glycocalyx may be another option, especially with biomarkers of glycocalyx degradation and shedding. Evaluation of the glycocalyx is still largely experimental, with different tools still in investigation and lack of therapeutic target. Venoarterial differences in PCO2 are inversely related with microvascular perfusion, and can thus be used as surrogate for microcirculation assessment. Several limitations prevent the regular use in clinical practice. The first is the difficult use of some of these techniques outside research teams, whereas nurse-driven measurements are probably desired. The second important limitation for daily practice use is the lack of uniformly defined endpoint. The final limitation is that therapeutic interventions affecting the microcirculation are not straightforward. Clinical and biological surrogates of microcirculatory assessment can be used at bedside. The role of microvideoscopic techniques is still hampered by the lack of clearly defined targets as well as interventions specifically targeting the microcirculation.