Microcirculatory dysfunction in critically ill patients: prevalence and significance from a bedside perspective

The microcirculation plays a pivotal role in oxygen delivery to the tissue. During the past decade, several studies have investigated microcirculatory dysfunction in critically ill patients. Main findings are a negative prognostic significance of microcirculatory alterations and the absence of a clear association between microcirculatory dysfunction and macrohemodynamic parameters. However, these studies were mainly restricted to high mortality subgroups such as cardiogenic and septic shock. This thesis aims to elaborate on the prevalence and significance in a general ICU population.
The main project described in this thesis is the ‘Microcirculatory Shock Occurrence in Acutely ill Patients’ study, a 36-center international study on the prevalence of microcirculatory alterations in intensive care patients. Microcirculatory dysfunction was not only associated with (relative) hyperlactatemia, but also with an increased risk of in-hospital death in patients with tachycardia, challenging the present paradigm of the dichotomy between microcirculation and macrocirculation. In addition, elevated central venous pressure appeared to be associated with impaired microvascular flow in a hypothesis generating post hoc analysis in septic patients. Lastly, a pilot study on the effect of the serotonin receptor antagonist ketanserin is described.
Concluding, the studies described in this thesis shed more light on the prevalence and significance of microcirculatory dysfunction in a general intensive care population. However, in order to proceed to a microcirculation centered resuscitation strategy further research is needed.