Microvascular monitoring - Do 'global' markers help?

The microcirculation is altered in sepsis, and the degree and persistence of these alterations are associated with outcome. When there are significant alterations of the systemic circulation, as in shock, the microcirculation is always altered. However, sometimes global variables can be restored to normal while the microcirculation remains altered. Monitoring the microcirculation has, therefore, been proposed as a more precise means of assessing the effects of therapy. In this review, we will discuss the limitations of global haemodynamic variables such as mean arterial pressure, cardiac output and mixed venous oxygen saturation as markers of microcirculatory abnormalities. We will also consider how these differences can be revealed during therapy.