Renal Replacement Therapy

Definition and ClassificationTop

Renal replacement therapy (RRT), more commonly known as dialysis, is a therapy for the treatment of renal failure, both in severe acute kidney injury (AKI) (see Acute Kidney Injury) and end-stage renal disease (ESRD) (see Chronic Kidney Disease), and in certain types of poisonings or overdoses. The dialysis modalities can be broadly classified into extracorporeal dialysis and peritoneal dialysis (PD).

Extracorporeal dialysis involves filtering the circulating blood through a semipermeable membrane in an apparatus outside of the patient’s body. Examples of commonly used modalities include:

1) Hemodialysis (HD) in its various forms (intermittent, short daily, nocturnal, home, in-center, hemodiafiltration). HD can be used for severe AKI and ESRD.

2) Continuous renal replacement therapy (CRRT), used in the critical care setting. CRRT may be considered in critically ill patients with renal failure who are hemodynamically unstable, often requiring multiple vasopressors and/or inotropes. It is much more resource intensive than HD. Examples include continuous venovenous hemodiafiltration (CVVHDF), continuous venovenous hemodialysis (CVVHD), continuous venovenous hemofiltration (CVVH), and slow continuous ultrafiltration (SCUF).

3) Sustained low-efficiency dialysis (SLED), a variation of HD that may be used in hospital, more often in the critical care setting as an alternative to CRRT, as it is less resource intensive.

Peritoneal Dialysis (PD): Dialysate is instilled into the peritoneal cavity; solutes diffuse from peritoneal capillaries, across the interstitium and mesothelium, into the dialysate. Ultrafiltration of fluid is achieved through an osmotic gradient created by the use of hypertonic dialysate, such as dextrose (glucose monohydrate).

PD is used mostly for ESRD. It is of limited use in adults with severe AKI due to several factors, such as lack of timely access to PD catheter insertions, increased risk of pericatheter leaking and resultant peritonitis, and inadequate solute and/or ultrafiltration in critically ill patients who are catabolic.

Chronic PD is a home-based therapy that can be performed by capable patients, their families, and/or assisting nurses where available.

IndicationsTop

Indications for RRT in AKI and ESRD include the presence of the following signs and symptoms that are refractory to medical therapy (often >1 sign or symptom is present): Fluid overload, hyperkalemia, metabolic acidosis, uremic pericarditis, uremic encephalopathy (including changes in mental status, confusion, seizures, and coma), uremic symptoms (nausea, vomiting, anorexia, weight loss, pruritus, fatigue, and lethargy), estimated glomerular filtration rate (eGFR) <10 mL/min/1.73 m2 of body surface area (BSA) in CKD with other uremic symptoms or metabolic derangements (see Hemodialysis; see Peritoneal Dialysis).

Considerations in Modality SelectionTop

In general, there are few absolute contraindications to RRT (see Hemodialysis; see Peritoneal Dialysis). An informed discussion with the patient and their families on the risks and benefits of RRT are required for the treatment of both severe AKI and ESRD. Factors affecting the selection of the RRT modality include the setting where the RRT is being provided (inpatient vs outpatient), available local resources, availability and suitability of access (vascular access for extracorporeal dialysis and peritoneal catheter for PD), suitability of home environment if home dialysis is desired (home HD and PD), and patient and family preferences including goals of care and quality of life considerations.