How do you correct various electrolyte imbalances?

Electrolyte Correction: Formulas and Rationale

Electrolyte correction requires precise calculation of deficits, careful monitoring during replacement, and attention to the rate of correction to prevent life-threatening complications—particularly for potassium, sodium, phosphate, and magnesium.

Hyperkalemia Correction

Immediate Management (K+ >6.5 mEq/L or ECG changes)

For severe hyperkalemia with cardiac toxicity, immediately administer IV calcium to stabilize the myocardial membrane, followed by therapies to shift potassium intracellularly, then promote excretion. 1, 2

Treatment sequence:

• Membrane stabilization: Calcium chloride 10% (10 mL IV over 2-3 minutes) or calcium gluconate 10% (30 mL IV over 5-10 minutes) 2
• Shift potassium intracellularly:
  • Regular insulin 10 units IV with 25g dextrose (D50W 50 mL) 2
  • Sodium bicarbonate 50-100 mEq IV (especially if metabolic acidosis present) 2
  • Nebulized albuterol 10-20 mg 2
• Promote excretion:
  • Furosemide 40-80 mg IV 2
  • Sodium polystyrene sulfonate (Kayexalate) 15-30g PO/PR (exchange ratio: 1 mEq K+ per 1 gram resin) 3
  • Hemodialysis for refractory cases 2

Critical monitoring: Continuous cardiac monitoring is mandatory, as hyperkalemia can rapidly progress to cardiac arrest. 1, 2

Pitfall: Always rule out pseudohyperkalemia from hemolysis or inadequate phlebotomy technique before aggressive treatment. 1

Hypokalemia Correction

Potassium Deficit Calculation

Formula: K+ deficit (mEq) = (Normal K+ - Measured K+) × body weight (kg) × 0.4

For every 1 mEq/L decrease in serum K+ below 3.5 mEq/L, total body deficit is approximately 200-400 mEq. 4

Replacement Strategy

• Use potassium chloride exclusively—avoid potassium citrate or other salts as they worsen metabolic alkalosis. 4
• IV replacement rate: Maximum 10-20 mEq/hour via peripheral line; up to 40 mEq/hour via central line with continuous cardiac monitoring 4
• Oral replacement: 40-100 mEq/day in divided doses 4
• Do not aim for complete normalization in Bartter syndrome or chronic conditions—target K+ 3.0-3.5 mEq/L to avoid excessive supplementation. 4

Rationale: Potassium chloride specifically corrects both the hypokalemia and the accompanying hypochloremic alkalosis commonly seen in these patients. 4

Hyponatremia Correction

Sodium Deficit Calculation

Formula: Na+ deficit (mEq) = (Target Na+ - Measured Na+) × body weight (kg) × 0.6 (males) or 0.5 (females)

Corrected sodium for hyperglycemia: Add 1.6 mEq/L to measured sodium for every 100 mg/dL glucose above 100 mg/dL. 4

Acute Symptomatic Hyponatremia (seizures, altered mental status)

Administer 3% hypertonic saline at 1-2 mL/kg/hour to raise sodium by 1-2 mEq/L/hour initially, then slow correction. 5

Critical rate limits:

• Maximum correction: 8-10 mEq/L in first 24 hours 5
• Never exceed 12 mEq/L in 24 hours to prevent osmotic demyelination syndrome 5

Chronic Hyponatremia Management

• Hypovolemic: 0.9% NaCl at 4-14 mL/kg/hour 4
• Hypervolemic: Fluid restriction, treat underlying cause (heart failure, cirrhosis) 5
• Euvolemic (SIADH): Fluid restriction to 800-1000 mL/day, consider vasopressin receptor antagonists 5

Hypernatremia Correction

Free Water Deficit Calculation

Formula: Water deficit (L) = body weight (kg) × 0.6 × [(Measured Na+/140) - 1]

Correction rate: Lower sodium by maximum 0.5 mEq/L/hour or 10-12 mEq/L per 24 hours using hypotonic fluids (0.45% NaCl or D5W). 5

Rationale: Overly rapid correction causes cerebral edema, particularly dangerous in chronic hypernatremia. 5

Hypophosphatemia Correction

Phosphate Deficit and Replacement

Severe hypophosphatemia (<0.32 mmol/L or <1.0 mg/dL) causes respiratory failure, cardiac arrhythmias, and rhabdomyolysis. 4, 2

IV replacement:

• Sodium phosphate or potassium phosphate 0.08-0.16 mmol/kg IV over 6 hours 4
• Monitor calcium levels—phosphate administration can precipitate hypocalcemia 4

Prevention in continuous renal replacement therapy (CRRT): Use phosphate-containing dialysis solutions (1.0-1.2 mmol/L phosphate) to prevent depletion. 4

Rationale: Hypophosphatemia occurs in 60-80% of ICU patients, particularly with intensive kidney replacement therapy, and prevention is superior to treatment. 4, 2

Hypomagnesemia Correction

Magnesium Replacement

Severe hypomagnesemia (<0.70 mmol/L) prolongs QT interval and causes ventricular arrhythmias. 4, 2

IV replacement:

• Magnesium sulfate 1-2g (8-16 mEq) IV over 15-60 minutes for severe deficiency 2
• Maintenance: 4-6g (32-48 mEq) per 24 hours 4

Oral replacement: Use organic magnesium salts (magnesium citrate, gluconate) for better bioavailability than magnesium oxide. 4

Prevention in CRRT: Use dialysis solutions with magnesium concentration 0.75-1.0 mmol/L, especially with citrate anticoagulation. 4

Critical relationship: Magnesium is essential for maintaining intracellular potassium—hypokalemia refractory to replacement suggests concurrent hypomagnesemia. 6

Hypocalcemia Correction

Calcium Replacement

Total body calcium deficit in DKA/HHS: 1-2 mEq/kg 4

IV replacement:

• Calcium gluconate 10% (1-2g or 10-20 mL) IV over 10 minutes for symptomatic hypocalcemia 4
• Maintenance: Add 20-30 mEq calcium to IV fluids 4

Rationale: Hypocalcemia commonly accompanies hyperphosphatemia in renal failure and must be corrected cautiously to avoid calcium-phosphate precipitation. 1

Special Considerations: Refeeding Syndrome

In severely malnourished patients, start feeding at 10 kcal/kg/day (not 20 kcal/kg/day) with generous electrolyte supplementation to prevent precipitous falls in potassium, phosphate, magnesium, and calcium. 4

Refeeding Protocol:

• Thiamine 100mg IV before feeding starts, continue for 3 days 4
• Generous supplementation: Potassium, magnesium, phosphate, calcium from day 1 4
• Monitor electrolytes every 6-12 hours for first 3-5 days 4

Rationale: Starvation causes intracellular electrolyte depletion (hundreds of mmol deficit). Refeeding triggers insulin-driven intracellular shift, causing life-threatening extracellular depletion and cardiac/respiratory failure. 4

Monitoring During Kidney Replacement Therapy

Electrolyte monitoring every 6-12 hours is essential in critically ill patients on CRRT, as 60-80% develop hypophosphatemia, 25% develop hypokalemia, and 60-65% develop hypomagnesemia. 4

Use dialysis solutions containing potassium (4 mEq/L), phosphate (1.0-1.2 mmol/L), and magnesium (0.75-1.0 mmol/L) to prevent depletion rather than treating deficiency. 4

Pitfall: Avoid IV electrolyte supplementation during CRRT—modulate dialysate composition instead for safer, more effective prevention. 4