What are the most common and significant toxicities and electrolyte imbalances that can be treated with hemodialysis, such as hyperkalemia (elevated potassium levels), hyperphosphatemia (elevated phosphate levels), and fluid overload?

Hemodialysis for Toxicities and Electrolyte Imbalances

Hemodialysis is most commonly and urgently indicated for life-threatening hyperkalemia, severe metabolic acidosis, volume overload unresponsive to diuretics, and uremic complications, with hyperkalemia representing the most immediately dangerous electrolyte emergency requiring dialytic intervention. 1

Primary Indications for Emergent Hemodialysis

Life-Threatening Electrolyte Abnormalities

Hyperkalemia is the most critical electrolyte disturbance requiring hemodialysis, particularly when persistent despite medical management or when causing cardiac instability. 1, 2

• Severe hyperkalemia (>6.0 mmol/L) or persistent hyperkalemia unresponsive to medical therapy (insulin/glucose, calcium, bicarbonate, potassium binders) mandates urgent dialysis 1
• Hemodialysis provides rapid potassium removal and is life-saving in preventing fatal arrhythmias and cardiac arrest 3
• Even moderate hyperkalemia (5.3-6.0 mmol/L) requires dialysis when accompanied by uremic symptoms or ECG changes 2

Hyperphosphatemia is effectively removed by hemodialysis, particularly in tumor lysis syndrome where phosphate levels exceed 6 mg/dL. 1

• Severe progressive hyperphosphatemia (>6 mg/dL) warrants prophylactic dialysis initiation before overt uremic symptoms develop 1
• Phosphate and uric acid are efficiently cleared by diffusive hemodialysis therapy 1

Acid-Base Disturbances

Severe metabolic acidosis unresponsive to bicarbonate therapy requires hemodialysis for rapid correction. 1, 4

• Hemodialysis efficiently corrects acidosis through bicarbonate-based dialysate 4, 5
• Metabolic acidosis commonly accompanies acute kidney injury and requires prompt dialytic intervention 4, 6

Volume Overload

Volume overload unresponsive to diuretic therapy is a critical indication for hemodialysis, particularly when causing pulmonary edema or respiratory compromise. 1

• Fluid removal through ultrafiltration during hemodialysis prevents life-threatening pulmonary edema 1
• Continuous renal replacement therapy may be preferred in hemodynamically unstable patients with severe volume overload 1, 2

Uremic Toxicities Requiring Dialysis

Uremic symptoms including encephalopathy, pericarditis, and neuropathy are absolute indications for immediate hemodialysis initiation. 1, 2

• Uremic neuropathy requires immediate dialysis as it represents advanced uremic toxicity that will not respond to conservative measures 2
• Uremic pericarditis and severe encephalopathy mandate urgent dialytic intervention 1

Specific Toxin Removal

Uric acid nephropathy responds rapidly to hemodialysis, with uric acid 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
• Oliguria from acute uric acid nephropathy often resolves as plasma uric acid falls to 10 mg/dL with dialysis 1

Dialysis Modality Selection

Intermittent hemodialysis (IHD) should be the initial modality for most patients requiring rapid solute and electrolyte removal. 1, 2

• 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 1, 2

Continuous renal replacement therapy (CRRT) should be reserved for specific clinical scenarios. 1, 2

• CRRT is preferred for hemodynamically unstable patients, as it causes less hypotension than intermittent hemodialysis 1, 2
• CRRT provides better control of azotemia, fluid overload, and allows improved nutritional support 1
• Potential CRRT indications include pulmonary edema, need for maintaining precise fluid balance, and facilitating nutritional therapy delivery 1

Peritoneal dialysis should be avoided when rapid solute removal is required, as it has significantly lower efficiency than hemodialysis or CRRT for removing potassium, phosphate, uric acid, and urea. 1

Common Pitfalls and Caveats

Hypocalcemia commonly accompanies hyperphosphatemia but should NOT be routinely treated with calcium supplementation, as this can worsen calcium-phosphate precipitation in tissues. 1

• Only symptomatic hypocalcemia (tetany, seizures) requires cautious calcium gluconate administration 1
• Asymptomatic hypocalcemia does not require treatment 1

Dialysate composition must be carefully selected to avoid inducing new electrolyte abnormalities during treatment. 5

• Rapid potassium removal can precipitate cardiac arrhythmias and requires careful monitoring 5
• Dialysate sodium, calcium, and buffer concentrations should be individualized based on the patient's specific electrolyte derangements 5

Rebound phenomena occur after hemodialysis, particularly with uric acid and phosphate, necessitating frequent dialysis sessions in conditions like tumor lysis syndrome. 1