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KEY POINTS
Renal replacement therapy (RRT) is one of the most expensive interventions used in an already cost burdensome intensive care unit (ICU) setting. Prescribing RRT in the critically ill is complex and ideally should involve clear communication between nephrologist and intensivist.
RRT modalities include peritoneal dialysis, intermittent hemodialysis, continuous renal replacement therapies, and sustained low-efficiency daily dialysis.
These modalities utilize 2 transport mechanisms in providing renal replacement: diffusion and convection. These forces result in solute clearance and plasma water removal or ultrafiltration (UF).
RRT is initiated early in patients whose renal function is not expected to quickly improve due to severity of illness and is unresponsive to resuscitation: multiorgan failure, high fractional excretion of sodium (FENa), rising azotemia (without plateau of urea or creatinine levels), and oliguria all suggestive of acute tubular necrosis (ATN).
At present, randomized trials and meta-analyses, do not support a mortality benefit for one modality over another. However, a gradual clearance rate may be wise in hemodynamic instability, acute coronary syndromes, elevated intracranial pressures (ICPs), or hypo/hypernatremia.
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Almost 60 years ago, RRT was first used to treat acute kidney injury (AKI) during the Korean War.1 Within 25 years, continuous therapies were first attempted in Germany.2 RRT modalities have since expanded, becoming commonplace in most hospitals of the developed world. In AKI, when preventative and supportive management fails we turn to RRT.
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In the past decade, admissions for AKI increased with a doubling in the incidence of severe AKI (Figure 31–1).3 In parallel, approximately 200,000 patients required RRT in 2012.3 The incidence of RRT-requiring AKI now surpasses that of end-stage renal disease (ESRD).4 What's more, the morbidity and mortality of AKI requiring RRT extends beyond hospitalization.3,5
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The necessity for RRT in the ICU arises in 1 of 3 clinical situations: AKI, critically ill ESRD patients,6 and drug or toxic overdoses. RRT for AKI is dramatic but less common than most think. The incidence of AKI in the ICU is relatively low between 6% and 19%, but can be higher depending on population studied and risk, injury, failure loss, and end-stage kidney disease (RIFLE) criteria.7,8 RRT needs occur in up to 5% of AKI....