Indications for Dialysis: A Mnemonic And Explanation

By: Neal Shah, Co-Editor-in-Chief

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Dialysis is the removal of substances from intravascular circulation by filtration.¹  Typically, dialysis is ordered when kidney function declines to 10–15% of normal function.²  The National Kidney Foundation’s Kidney Disease Outcome Quality Initiative (K/DOQI) recommends that planning for dialysis begin when patients reach chronic kidney disease stage 4, which is when glomerular filtration rate or creatinine clearance reaches below below 30 mL/min.³  However, this is not the only indication for the initiation dialysis.  A subset of acute and chronic renal failure indications are provided below:⁴

Indications of dialysis in acute renal failure (ARF)

• Severe fluid overload
• Refractory hypertension
• Uncontrollable hyperkalemia
• Nausea, vomiting, poor appetite, gastritis with hemorrhage
• Lethargy, malaise, somnolence, stupor, coma, delirium, asterixis, tremor, seizures,
• Pericarditis (risk of hemorrhage or tamponade)
• bleeding diathesis (epistaxis, gastrointestinal (GI) bleeding and etc.)
• Severe metabolic acidosis
• Blood urea nitrogen (BUN) > 70–100 mg/dl

Indications of dialysis in chronic renal failure (CRF)

• Pericarditis
• Fluid overload or pulmonary edema refractory to diuretics
• Accelerated hypertension poorly responsive to antihypertensives
• Progressive uremic encephalopathy or neuropathy such as confusion, asterixis, myoclonus, wrist or foot drop, seizures
• Bleeding diathesis attributable to uremia

A simple mnemonic is used to remember the indications for dialysis: A-E-I-O-U.⁵

The normal bodily pH averages 7.4.  Respiratory centers act to maintain the pH between 7.35 and 7.45 and the kidneys act to remove bicarbonate or ammonium in response to acid-base changes.  In severe kidney disease, this homeostatic mechanism is disrupted, and the body can rapidly turn acidotic or alkalotic regardless of compensation from the respiratory centers.  This acid-base problem is an indication for dialysis, where these molecules can be removed and normal pH can be restored.⁶

The kidneys normally actively secrete potassium from the distal convoluted tubule and loops of Henle.  When kidney failure or injury sets in, hyperkalemia can easily develop.  Symptoms of hyperkalemia include fatigue, myalgia, and muscular weakness.  Severe hyperkalemia can present as tented T-waves on an EKG and progression to ventricular fibrillation.  Dialysis removes excess potassium from the bloodstream and returns the body back down to physiological levels.⁶

Overdose and intoxication of substances that are found in the blood may be an indication for dialysis.  These drugs should have a low volume of distribution and shouldn’t be highly bound to plasma proteins.  Unfortunately, some common overdose or intoxicant drugs like digoxin and tricyclic antidepressants have volumes of distribution in hundreds of liters, and are not readily removed by dialysis.⁶  Ethanol is easily removed via dialysis, as are some anti retroviral drugs, aminoglycosides, and antibiotics.⁷

Indications for fluid resuscitation are numerous, ranging from hypovolemia to hypotension.⁶  When patients regain clinically acceptable statuses, the fluids administered are then considered to be fluid overloads, and should be removed to prevent iatrogenic heart failure.  Dialysis can be used to remove excess fluids from patients’ bodies.

Uremia often develops in chronic kidney failure, brought on by the inability to excrete nitrogenous wastes, parathyroid hormone, proteins and other physiological substances in toxic levels.⁸  Since these substances are floating in the bloodstream, dialysis can easily clear the body of these toxins to restore physiological homeostasis.

SOURCES:

1. Dialysis. Available at: http://www.nlm.nih.gov/medlineplus/dialysis.html, Accessed August 5, 2012.
2. Dialysis. Available at: http://www.kidney.org/atoz/content/dialysisinfo.cfm, Accessed August 5, 2012.
3. Sowinski KM and Churchwell MD. Pharmacotherapy: A Pathophysiologic Approach, 8th edition. Section 5. Renal Disorders, Chapter 54. Hemodialysis and Peritoneal Dialysis. http://www.accesspharmacy.com/content.aspx?aID=7982188, accessed August 5, 2012. 2011 by The McGraw-Hill Companies, Inc. Accessed August 5, 2012.
4. Firman, G. Indications of Dialysis in Renal Failure. http://www.medicalcriteria.com/site/index.php?option=com_content&view=article&id=245%3Anephdrf&catid=63%3Anephrology&Itemid=80&lang=en, Accessed August 5, 2012.
5. Palmer M. Dialysis: Indications. http://www.medicalmnemonics.com/cgi-bin/return_browse.cfm?discipline=Urology%20%2F%20Nephrology&browse=1, Accessed August 5, 2012.
6. Fauci A, Kasper D, Longo D, et al. Harrison’s Principles Of Internal Medicine, 17th edition. Chaper 48. Acidosis and Alkalosis. 2008, The McGraw-Hill Companies, Inc. Accessed August 5, 2012.
7. Bailie, GR and Mason, NA. 2012 Dialysis of Drugs. Renal Pharmacy Consultants, LLC. Saline, Michigan.
8. Alpner, AB. Uremia. http://emedicine.medscape.com/article/245296-overview#a0101, Accessed August 5, 2012.