Renal replacement therapy

Last updated: June 28, 2022

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Renal replacement therapy (RRT) is used to support or replace kidney function (i.e., remove toxins, metabolites, and/or water from the body). RRT is indicated in various acute (e.g., acute renal injury, poisoning, refractory fluid overload) and chronic conditions (e.g., chronic kidney disease). There are three main RRT modalities: dialysis (either hemodialysis or peritoneal dialysis), hemofiltration, and kidney transplantation. The choice of RRT depends on the anticipated duration of treatment (acute RRT vs. chronic RRT), indications for treatment, patient characteristics, and patient preference. Dialysis uses diffusion to remove solutes from the blood across a semipermeable membrane, while hemofiltration uses convection; both modalities employ varying degrees of ultrafiltration to remove water. Kidney transplantation is the most comprehensive method of RRT in patients with end-stage renal disease (ESRD) and is covered separately in “Transplantation.”

Approach [1]

The following is applicable for all patients in whom acute or chronic RRT is being considered.

RRT should be initiated before potentially life-threatening complications of renal failure develop. [2]

Indications for RRT [3][4][5]

Indications for urgent RRT: “A.E.I.O.U.” -Acidosis, Electrolyte abnormalities (hyperkalemia), Ingestion (of poisons), Overload (fluid), Uremic symptoms

Dialyzable medications and poisons: “I STUMBLED” - Isoniazid, isopropyl alcohol; Salicylates; Theophylline, Tenormin® (atenolol); Urea; Methanol; Barbiturates; Lithium; Ethylene glycol; Dabigatran, Depakote®(valproic acid)

RRT mechanisms and modalities [2][7][8]

Select the RRT modality based on therapeutic goals, availability, and local expertise. Kidney transplantation is covered separately in “Transplantation.”

Mechanisms

  • Diffusion
    • Solutes move across a semipermeable membrane down their concentration gradient.
    • Smaller molecules have faster rates of diffusion and are cleared more easily.
  • Convection
    • Hydrostatic pressure gradients drive water (i.e., ultrafiltration) and solutes across a semipermeable membrane.
    • Solutes of all sizes can be effectively cleared; the solutes cleared depends on the pore size in the filter membrane.

Modalities

Comparison of renal replacement therapies [3][7][9]
Peritoneal dialysis Hemodialysis

Hemofiltration

Substances removed [8]
  • Small solutes
  • Some water
  • Solutes of all sizes (most effectively removes medium and large solutes)
  • Water
Mechanism [8]
Access
Indications
  • Chronic RRT
  • No venous access
  • Preferred modality in candidates for home dialysis
  • Acute or chronic RRT
  • Preferred in patients who require:
    • Clearance of large molecules
    • Precise fluid control [2]
Disadvantages and complications

Basic principles [2][9][10]

  • Hemodialysis: utilizes diffusion and a small degree of ultrafiltration to remove solutes and water from the blood
    • More effective at removing small molecules (e.g., urea, creatinine, ammonia) than larger molecules
    • Blood is pumped through the dialysis unit on one side of a semipermeable membrane and dialysate in the opposite direction on the other side of the membrane.
    • Molecules diffuse across the semipermeable membrane down their concentration gradient.
  • Hemofiltration: utilizes convection and a high degree of ultrafiltration to remove solutes and water from the blood
    • More effective at removing medium to large molecules (e.g., cytokines, myoglobin) than hemodialysis [10]
    • Blood is pumped through a machine and the difference in hydrostatic pressures drives water and solutes across a semipermeable membrane.
    • Lost plasma volume is replaced with a physiologic crystalloid solution. [2]
  • Hemodiafiltration
    • Combination of hemodialysis and hemofiltration
    • Removes molecules of all sizes (most effective method for medium-sized molecule clearance)
  • Administration options
    • Intermittent renal replacement therapy
      • Typically occurs over 3–5 hours; may last 6–18 hours (prolonged intermittent renal replacement therapy) [2][7]
      • Most common option for outpatient administration in patients with CKD; also used for acute RRT [7]
    • Continuous renal replacement therapy [7]
      • Gradual fluid and solute clearance over 24 hours
      • Used almost exclusively for acute RRT
      • Preferred if fluid shifts are contraindicated [3]

Intermittent RRT can be performed in a clinic or at home by the patient after adequate training.

Access [1][3][11]

Consider the anticipated duration of RRT and patient factors (e.g., preference, life expectancy, mobility) to determine the most appropriate type of access for RRT.

Venous catheter for renal replacement therapy

Arteriovenous access [11]

AV fistulas need approximately 4–6 weeks to mature (i.e., enlargement and thickening of the vein in response to arterial pressure); maturation is unsuccessful in up to 60% of patients. Arrange AV access before dialysis is likely to be required. [11]

Complications [2][7][11]

Vascular access complications [11]

Cardiovascular complications [2]

Increased bleeding risk [16]

Dialysis disequilibrium syndrome [3][17]

Other complications [2][7]

Cardiovascular disease is the leading cause of death in patients on dialysis and kidney transplant recipients. [5]

Basic principles [2][22]

  • Mechanism: utilizes diffusion across the peritoneum (acts as a semipermeable membrane) and ultrafiltration to remove water and solutes from the blood
  • Procedure
    • Dialysate is instilled into the abdomen and left for a set period of time (i.e., dwell time) to allow diffusion.
    • Hypertonic dialysate draws water across the peritoneal membrane via osmosis.
    • The effluent is removed at the end of the dwell time.
  • Administration options: self-administered by highly adherent patients (or their carers) at home [23]
    • Continuous ambulatory peritoneal dialysis
      • Performed manually 3–5 times/day
      • No requirement to be connected to a machine
    • Automated peritoneal dialysis
      • Automated exchange cycles, typically scheduled overnight
      • Patients are connected to a machine.
  • Peritoneal catheter
    • Location: placed into the peritoneal cavity and tunneled to an exit site [22]
    • Placement: laparoscopic, percutaneous (with or without image guidance), or open surgical approach

Because of the high risk of complications, individuals must be trained and able to demonstrate strict adherence to correct techniques before being allowed to perform home peritoneal dialysis. [2]

Complications [2][22][24]

Frequently examine the peritoneal dialysis catheter and exit site for signs of infection (e.g., swelling, purulent drainage); consider ultrasound for a more detailed assessment if infection is suspected. [24]

Risk factors [29]

Clinical features [29]

Diagnostics [29]

Initiate empiric antibiotic therapy for presumed peritonitis in all patients with cloudy peritoneal effluent, even if they are asymptomatic. [29]

Management [29][31][32]

Initial management

Ongoing management

Prevention [29]

Educate patients to monitor effluent characteristics at home and seek medical attention if they observe any changes suggestive of peritonitis (e.g., cloudiness).

Contact nephrology and/or a pharmacist for all medication dosing and if clinical management may affect or be affected by RRT.

Do not access any RRT lines except in an emergency, if no other access is available.

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