The microcirculation as a clinical concept: work in progress

Purpose of review The present review discusses the evolution of the microcirculation from a theoretical idea to a clinical concept, as a result of the introduction of direct in-vivo observation techniques. Recent findings Technical proceedings in the acquisition and assessment of microcirculatory imaging are described, as well as the first report of in-vivo mitochondrial pO(2) measurements. Experimental data on immune tolerance, leukocyte dynamics, vascular permeability and regional hypoxia have contributed to unravel the complex origin of microcirculatory alterations. Several reports have highlighted the concept of heterogeneity of microcirculatory blood flow observed within and between different microvascular beds. The previously reported prognostic value of microcirculatory alterations has now been expanded to the early phase of sepsis and in postoperative patients. Finally, a list of interventions in experimental and clinical settings is discussed with regard to their potency to influence microcirculatory changes in shock. Summary Direct in-vivo observation of the microcirculation has enabled the construction of microcirculatory failure as a clinical concept in the critically ill. Aiming for promicrocirculatory recruitment strategies in order to improve outcome will be the challenge for the near future.