Microcirculatory blood flow as a new tool for perioperative fluid management

Abstract

Microcirculatory alterations often occur in the perioperative setting under the influence of multiple factors including hypovolemia, impaired cardiac function, vasoplegia, anesthetic agents, surgical trauma, ischemia/reperfusion injury, and sepsis. The severity and duration of these alterations have been related to the outcome of these patients. This systematic review will report to which extent these microvascular abnormalities can be affected by fluid administration. Administration of fluids usually improves microvascular dysfunction by increasing the perfused capillary density. Importantly, there is a significant variability among the patients. Timing of the intervention has a huge impact, as early interventions often lead to an improved microvascular perfusion, while delayed intervention often fails to improve the microcirculation. Of note, the impact of fluids on the microcirculation is relatively dissociated from its systemic effects and can thus not be predicted by changes in cardiac output or blood pressure. Changes in lactate or in venoarterial PCO2 gradients can be useful to indirectly evaluate the microvascular effects of fluids. Even though colloids are often associated with greater effects than crystalloids in experimental settings, this has not been confirmed in patients. Finally, the impact of red blood cell transfusions is highly variable and may depend on the severity of microvascular alterations at baseline.