Effect of Fluid Challenge on Glycocalyx

Effect of two regimes of fluid challenge on GCX in patients with sepsis and during elective surgery under general anesthesia. Hypothesis to be tested: Administration of 500 ml of balanced solution as a bolus impairs GCX more than prolonged administration. The aim of the study: Comparison of two regimes of fluid challenge in patients with sepsis and in patients undergoing elective major surgery. Type of the study: Open, randomized, interventional. Subjects: Part A: Patients with sepsis within 48 hours before admission to ICU requiring fluid challenge based on clinical or echocardiographic assessment. Part B: Patients during major elective surgery requiring fluid challenge based on clinical or echocardiographic assessment. Sample size calculation (based on expected difference in PRB, alpha error I =0,05 and study power = 0,99) = 52 patients. Investigators plan enrolment of 60 patients for each part, totally 120 patients. Intervention: ‐ 500 ml of balanced crystalloid solution within 5 minutes (group "fast") ‐ 500 ml of balanced crystalloid solution within 30 minutes (group "slow") Data to be recorded and analysed: Demographics, severity score, fluid response assessment, sublingual microcirculation by SDF imaging will be recorded at time points: baseline, after intervention, after 60 minutes, after 120 minutes, plasma syndecan‐1 will be analysed before intervention and 120 minutes thereafter, microcirculatory data and Perfused Boundary Region.