What are the primary indications for hemodialysis, using the AEIOU (Acidosis, Electrolyte imbalance, Intoxication, Overload, Uremia) mnemonic?

Indications for Hemodialysis: The AEIOU Mnemonic

Yes, the AEIOU mnemonic accurately captures the primary life-threatening indications for emergent hemodialysis: Acidosis (severe metabolic), Electrolyte abnormalities (particularly hyperkalemia), Intoxication (dialyzable toxins), Overload (volume), and Uremia (symptomatic). 1, 2

A - Acidosis (Severe Metabolic)

Severe metabolic acidosis with pH <7.20 despite maximal medical management requires hemodialysis. 2

• Persistent severe metabolic acidosis unresponsive to bicarbonate therapy in acute or chronic kidney disease mandates dialytic intervention 3, 2
• The combination of acidosis with life-threatening hyperkalemia (>6.0 mmol/L) represents an absolute indication for urgent dialysis 2
• In toxic ingestions (salicylates, ethylene glycol), severe acidemia warrants immediate extracorporeal treatment regardless of toxin concentration 2

E - Electrolyte Abnormalities (Primarily Hyperkalemia)

Hyperkalemia is the most immediately dangerous electrolyte emergency requiring dialytic intervention. 1

• Severe hyperkalemia (>6.0 mmol/L) or persistent hyperkalemia unresponsive to medical therapy mandates urgent dialysis 1
• Even moderate hyperkalemia (5.3-6.0 mmol/L) requires dialysis when accompanied by uremic symptoms or ECG changes 1
• Severe progressive hyperphosphatemia (>6 mg/dL) warrants prophylactic dialysis initiation before overt uremic symptoms develop 3, 1

Critical pitfall: Hypocalcemia commonly accompanies hyperphosphatemia but should NOT be routinely treated with calcium supplementation, as this worsens calcium-phosphate precipitation in tissues. 1, 2 Only symptomatic hypocalcemia (tetany, seizures) requires cautious calcium gluconate administration. 1, 2

I - Intoxication (Dialyzable Toxins)

Hemodialysis efficiently removes specific dialyzable toxins through diffusive clearance. 1

• Uric acid nephropathy responds rapidly to hemodialysis, with clearance of approximately 70-100 mL/min during treatment 1
• Plasma uric acid levels fall by approximately 50% with each 6-hour hemodialysis treatment 1
• Salicylate and ethylene glycol poisoning with severe acidemia require immediate hemodialysis 2

O - Overload (Volume)

Volume overload unresponsive to diuretic therapy is an absolute indication for hemodialysis. 3, 1, 2

• Volume overload accompanied by pulmonary edema requires urgent dialytic intervention 3
• The appearance of pulmonary edema represents a potential indication for continuous renal replacement therapy (CRRT) in hemodynamically unstable patients 3
• Fluid overload with concurrent severe metabolic acidosis mandates immediate hemodialysis 2

U - Uremia (Symptomatic)

Uremic symptoms represent absolute indications for immediate hemodialysis initiation. 1

• Uremic encephalopathy requires immediate dialysis as it represents advanced uremic toxicity that will not respond to conservative measures 1
• Uremic pericarditis mandates urgent dialytic intervention 3, 1
• Uremic neuropathy requires immediate dialysis 1
• Severe encephalopathy with altered mental status is an absolute indication 3

Dialysis Modality Selection

Intermittent hemodialysis (IHD) should be the initial modality for most patients requiring rapid solute and electrolyte removal. 1

• IHD provides superior efficiency for removing uric acid, urea, potassium, and phosphate compared to peritoneal dialysis 1
• Frequent (daily) dialysis is recommended when there is continuous release of metabolites and electrolytes, such as in tumor lysis syndrome 3, 1
• CRRT should be reserved for hemodynamically unstable patients, as it provides better control of azotemia and fluid overload with less tendency to exacerbate hypotension 3, 1
• Peritoneal dialysis should be reserved for situations where other therapy modalities are unavailable, as it has lower efficiency for solute and fluid removal 3

Common Pitfalls

Avoid routine calcium supplementation in hyperphosphatemia: This worsens tissue calcium-phosphate precipitation. 1, 2 Only treat symptomatic hypocalcemia with cautious calcium gluconate. 1, 2

Monitor for rebound hyperkalemia: In tumor lysis syndrome or ongoing cell lysis, frequent (daily) dialysis may be necessary due to continuous release of potassium and other metabolites into the bloodstream. 3, 1

Recognize the "lag phenomenon": Blood pressure may not decrease immediately after fluid removal in some patients, requiring repeated ultrafiltration sessions for eventual control. 3