Microcirculatory Effects of Methylene Blue

"Each of the variable related to macro- and microcirculatory will be evaluated before and one hour after start of MB infusion.~Macrocirculatory parameters will include :~* Mean, systolic, diastolic arterial, heart rate (HR)~* Cardiac output (CO), sequential vascular response (SVR) and stroke volume (obtained with transthoracic echocardiography or transpulmonary thermodilution catheter if available).~* A passive leg raising (PLR) test will be performed before and one hour after MB infusion. Patients will be classified as fluid responder if they had a CO of at least 10% after PLR.~Microcirculatory parameters will include :~* Cutaneous and gingival refill time~* Tissue oxygen saturation combined with vascular occlusion test (VOT)~* Video microscopy measurements of the sublingual microcirculation~* Metabolic variables: Arterial blood gases including arterial lactate and central venous blood gases."