Renal replacement therapies in perioperative intensive care units

Background: Perioperative acute kidney injury (AKI) is a major complication following surgery and associated with a considerably increased rate of morbidity and mortality. Therefore, it is essential to identify patients who are at risk before surgery. Besides general nephroprotective measures, the therapy of AKI with organ failure, ranging from severe functional impairment to loss of function with excess fluids, uraemia, electrolyte imbalance or metabolic acidosis frequently requires a renal replacement therapy (RRT) during ICU treatment. The management of patients with perioperative AKI requires a multidisciplinary approach. In perioperative intensive care units intensivists are routinely involved in the prescription and delivery of extracorporal RRT in patients with AKI. This review article describes the basic principles underlying extracorporal renal replacement therapies frequently used in the treatment of AKI in adults on non-nephrologist intensive care units. Furthermore, this article provides a description of the RRT treatment modalities and the physical principles of fluid and solvent transport. Methods: This review article is based on a literature search in PubMed for pertinent publications on AKI. Special attention is drawn to updated classification criteria and the current international KDIGO guidelines. Results: Perioperative AKI is associated with considerable mortality and morbidity. Perioperative identification of patients at high risk, prevention and early diagnosis are essential for an interdisciplinary therapy approach. The choice of RRT modality should be influenced by haemodynamic stability and patients' comorbidities as well as by the clinical expertise of the physicians and logistics. Current evidence concerning timing of renal replacement therapy in critical ill patients is insufficient. The indication to start renal replacement therapy should be influenced by individual benefit-risk-profiles and the severity of comorbidities. Conclusion: This review article provides the principles of extracorporal renal replacement therapy. Special attention is drawn to modalities of dialysis and typical clinical aspects.