[Focus on Albumin: new perspectives for the clinical application in intensive care medicine : From the quantitative routine to qualitative individualized theranostics].

Human albumin plays a double role in intensive care medicine. It is therapeutically administered as a colloid and diagnostically employed as a laboratory parameter for risk and monitoring classification. For both fields of application, a quantitative logic has so far been dominant. Large randomized studies consistently show that human albumin is overall safer than crystalloids but does not provide a general benefit in most intensive care medical scenarios. Subgroup-specific risks must be considered: in cases of traumatic brain injuries the administration of hypotonic 4% albumin solution was associated with an increased mortality; new analyses indicate that the hypotonicity of the solution in particular and not the albumin molecule per se was the decisive risk factor. A target value-based albumin strategy also does not lead to any advantage with respect to mortality in cases of sepsis. Accordingly, current guidelines and international consensus recommendations position albumin as a targeted supplement after administration of crystalloids and not as first-line treatment.Parallel to the established evidence, the interest in a qualitative albumin perspective is growing. In cases of sepsis and septic shock albumin is not only quantitatively reduced but its function as transport and binding protein can also be measurably impaired. The term theranostics can be understood as an integrated approach in which a functional assay captures the individual albumin phenotype from which a phenotype-specific intervention can be derived and the success of treatment can be monitored based on the same parameters. Practical examples, from altered pharmacokinetics of furosemide in cases of reduced binding capacity to the differentiated assessment of albumin formulations in cases of brain injury, illustrate the concept. Taken as a whole, the available evidence indicates a paradigm shift away from the purely quantitative consideration to functional phenotype-based albumin theranostics, where the clinical benefits must be confirmed in prospective multicenter studies.