CPB Prime Fluid Strategies to Preserve Mcirocirculatory Perfusion

Acute microcirculatory perfusion disturbances is common in critical illness and associated with higher morbidity and mortality. Recent findings by the investigators' group showed that microcirculatory perfusion is disturbed during cardiac surgery with cardiopulmonary bypass (CPB) and remain disturbed up to 72 (seventy two) hours after surgery. A cardiopulmonary bypass is a machine which takes over heart and lung function, during the procedure. The disturbed microcirculation is associated with organ dysfunction induced by cardiac surgery using CPB, which is frequently seen (up to 42%, forty two percent) and results in a six-fold increase in mortality rate. The underlying cause of disturbed microcirculation is a higher endothelial permeability and vascular leakage and are a consequence of systemic inflammation, hemodilution (dilution of blood), hypothermia and hemolysis (breakdown of red blood cells). To gain the knowledge regarding disturbed microcirculation the investigators previously showed that hemodilution attributes to this disturbed perfusion. Hemodilution lowers colloid oncotic pressure (COP). Also, COP is affected by free hemoglobin, which increases with hemolysis and attributes to a disturbed microcirculation following CPB. This is interesting, as to the best of our knowledge, the effect of minimizing hemodilution and hemolysis during cardiac surgery on the microcirculatory perfusion has never been investigated, but could be the key factor in reducing organ dysfunction.

In this project the investigators focus on reducing microcirculatory perfusion disturbances by exploring therapeutic approaches with different prime fluid strategies, by acting on COP (part I) and free hemoglobin scavenging with human albumin (part II). In part I, patients undergoing elective coronary artery bypass graft (CABG) surgery with cardiopulmonary bypass will be randomized in three groups receiving different prime fluid strategies. The study endpoint is the reduction in functional capillary density during the perioperative period. Sublingual microcirculatory measurements and blood sampling will take place after induction of anesthesia, during and after surgery to determine microcirculatory perfusion and parameters for hemodilution, hemolysis, COP, markers for endothelial damage and glycocalyx shedding. Measurements start on the day of surgery and end one day after surgery. In part II, participants will be randomized in two groups receiving the first dose directly after aortic cross clamping and blood cardioplegia administration, and the second dose after the third blood cardioplegia administration (± 30 min after the first dose).The most optimal prime fluid in order to preserve microcirculatory perfusion from study one, will be used as prime fluid in the second study. Microcirculatory perfusion parameters will be measured at time points comparable with study one. Blood samples are taken to determine markers for hemodilution, hemolysis, COP and endothelial damage and glycocalyx shedding. For part II see trial registration: PRIME, part II.