Contributions to nephrology
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Different definitions for acute kidney injury (AKI) once posed an important impediment to research. The RIFLE consensus classification was the first universally accepted definition for AKI, and has facilitated a much better understanding of the epidemiology of this condition. The RIFLE classification was adapted by a broad platform of world societies, the Acute Kidney Injury Network group, as the preferred AKI diagnostic and staging system. ⋯ Renal replacement therapy is necessary in approximately 2% of this cohort. AKI that occurs within a 7-day period after cardiac surgery is related to perioperative risk factors, such as preexisting chronic kidney disease, acute ischemia, aorta cross-clamping, or use of cardiopulmonary bypass. AKI that occurs after the first week is mostly a consequence of sepsis or heart failure.
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Renal replacement therapy (RRT) is an important therapeutic and supportive measure for acute kidney injury (AKI) in the critical care setting. While RRT is extensively used in clinical practice, there remains uncertainty about the ideal circumstances of when to initiate RRT and for what indications. Many factors, including logistics, resource availability, physician experience and patient-related factors are involved in the decision of when to start and stop RRT for those with AKI. ⋯ This algorithm was developed using available clinical evidence, recognizing the inherent limitations of observational studies. It aims to provide a starting point for clinicians and future prospective studies. We also review the available literature on discontinuation of RRT and propose a few simple recommendations on how to 'wean' patients from RRT.
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Intravenous fluids are commonly administered to patients with developing septic acute kidney injury (AKI). Conversely, fluids are just as commonly removed with diuretics or renal replacement therapy (RRT) techniques or ultrafiltration in patients with cardiorenal syndromes (CRS). In both groups, there is controversy regarding fluid management. ⋯ However, in patients with either septic AKI or CRS, hypovolemia and renal hypoperfusion can occur if excessive fluid removal is pursued with diuretics or extracorporeal therapy. Thus, accurate assessment of fluid status and careful definition of targets are needed to improve clinical outcomes. Controlled studies of conservative versus liberal fluid management in patients with AKI or CRS seem justified.
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Extracorporeal therapies are able to sustain life through different mechanisms. This approach, called multiple organ support therapy, can in fact obtain blood purification by hemodialysis/hemofiltration to replace kidney function, temperature control, electrolyte and acid-base control to mimic homeostatic regulation of the kidney and circulation, fluid balance control to support the right hydration and cardiac performance, cardiac support removing cardiodepressant substances and equilibrating potassium levels, blood detoxification and liver support by coupled plasma filtration and adsorption or direct adsorption on blood (hemoperfusion), immunomodulation and endothelial support in the presence of sepsis by cutting the peaks of pro- and anti-inflammatory mediators, and immunoadsorption or adsorption of specific substances such as endotoxin. ⋯ Today this is made possible by removal of CO(2) either by complete extracorporeal membrane oxygenation or by using decapneization in conjunction with hemofiltration in a system called DECAP/DECAPSMART. In conclusion, circulating blood outside the body and treating it with different filters or cartridges in a multiple organ support therapy may represent an important support for multiple organ dysfunction conditions induced by sepsis, acute respiratory distress syndrome and in recent times by complicated H1N1-related infections.
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Endotoxin removal by polymyxin B immobilized cartridge inactivates circulating proapoptotic factors.
Severe sepsis and septic shock continue to be major clinical challenges due to high associated mortality. Lipopolysaccharide (LPS) is a component of the cell membrane of Gram-negative bacteria, and is believed to initiate septic-induced signaling, inflammation and organ damage, including acute renal failure. Polymyxin B (PMX-B) hemoperfusion of septic patients can improve survival and decreasing organ dysfunction by removing circulating LPS. Unfortunately, some clinicians have been slow to adopt this novel therapy due to the lack of understanding of the cellular mechanisms involved in this treatment. Apoptosis, or programmed cell death, is known to contribute to acute renal failure and overall organ dysfunction during sepsis, and can be activated by LPS-initiated signaling pathways. Therefore, the protective renal effects associated with PMX-B hemoperfusion of septic patients may result from alterations in cellular apoptosis. This chapter will review recent data regarding the role of apoptosis prevention in the mechanism leading to the improved outcome and decreased acute renal failure associated with PMX-B hemoperfusion during sepsis. ⋯ The protective effects of extracorporeal therapy with PMX-B on the development of acute renal failure result, in part, through its ability to reduce the systemic proapoptotic activity of septic patients on renal cells.