What is the management for a 3-week-old neonate with hyperkalemia (elevated potassium level) and 2+ hemolysis?

Management of Pseudohyperkalemia in a 3-Week-Old Neonate

This is almost certainly pseudohyperkalemia from hemolysis, not true hyperkalemia, and should be managed by repeating the blood draw with meticulous technique rather than treating the potassium level. 1, 2

Immediate Assessment: Distinguish True from False Hyperkalemia

The presence of 2+ hemolysis makes this result unreliable and likely artifactual. In a retrospective analysis of 145 pediatric patients with hemolyzed samples showing hyperkalemia, 97.9% had normal potassium on repeat testing, and all 3 patients (2.1%) with true hyperkalemia had underlying conditions predisposing to hyperkalemia 2. Hemolysis releases intracellular potassium (which is 30-40 times higher than extracellular levels) into the serum sample, creating falsely elevated readings 1.

Critical Clinical Indicators to Assess NOW:

• Check the ECG immediately - True hyperkalemia at 6.5 mmol/L would show peaked T waves, prolonged PR interval, widened QRS, or loss of P waves 3, 4. If the ECG is normal, this strongly suggests pseudohyperkalemia 3.

• Assess clinical status - A well-appearing 3-week-old with normal vital signs, normal urine output (>0.5 mL/kg/hour), and no signs of distress argues against true hyperkalemia 5, 6.

• Review risk factors for true hyperkalemia - Extreme prematurity (<1000g birth weight), acute kidney injury (elevated creatinine/BUN), metabolic acidosis, recent blood transfusion, or medications containing potassium would increase suspicion for true hyperkalemia 4, 6.

Recommended Management Algorithm

If ECG is NORMAL and infant is clinically well:

Repeat the potassium level immediately using proper technique: 2

• Use free-flowing venous or arterial blood (avoid heel stick or difficult draws) 1
• Minimize tourniquet time and avoid "milking" the extremity 1
• Process sample promptly without delay 1
• Request laboratory to report degree of hemolysis 2

Do NOT treat empirically while awaiting repeat results if the infant has normal renal function (normal BUN/creatinine), normal urine output, and no underlying conditions predisposing to hyperkalemia 2. The 2% risk of true hyperkalemia in this scenario does not justify the risks of unnecessary treatment 2.

If ECG shows changes OR infant has risk factors for true hyperkalemia:

Treat as true hyperkalemia emergently while obtaining repeat sample: 3, 4

1. Stabilize cardiac membranes (onset 1-3 minutes): 3

   • Calcium gluconate 10%: 100-200 mg/kg (1-2 mL/kg) IV over 5-10 minutes with continuous cardiac monitoring 3, 4
   • Repeat dose if no ECG improvement within 5-10 minutes 3
   • This does NOT lower potassium but protects against arrhythmias 3

2. Shift potassium intracellularly (onset 30-60 minutes): 3, 5

   • Regular insulin 0.1 units/kg IV with glucose 0.5-1 g/kg (5-10 mL/kg of 10% dextrose) over 30-60 minutes 3, 5
   • Monitor blood glucose every 30 minutes for 4 hours to prevent hypoglycemia 3
   • Alternative: Albuterol nebulization 0.4 mg/kg (max 10 mg) can reduce potassium by 0.69 mmol/L at 4 hours 5

3. Enhance elimination (onset 1-2 hours): 3, 4

   • Sodium polystyrene sulfonate (Kayexalate) 1 g/kg rectally as retention enema 4
   • Avoid furosemide in neonates - limited efficacy, risk of metabolic alkalosis, nephrocalcinosis, and ototoxicity 7
   • Consider exchange transfusion if potassium remains >7 mmol/L despite above measures or if hemodynamic instability present 4

4. Correct hypomagnesemia if present: 3

   • Magnesium sulfate 25-50 mg/kg IV over 2-4 hours, targeting magnesium >0.6 mmol/L 3

5. Stop all potassium sources: 3

   • Discontinue any IV fluids containing potassium until serum potassium <5.5 mmol/L 3, 8
   • Review all medications for potassium content 3

Monitoring Protocol

• Recheck potassium within 1-2 hours after insulin-glucose therapy, then every 2-4 hours until stable <5.5 mmol/L 3
• Continuous cardiac monitoring until potassium normalizes 3, 4
• Monitor blood glucose, calcium, and magnesium 3, 4
• Assess urine output (target >0.5 mL/kg/hour) 5, 6

Critical Pitfalls to Avoid

• Never treat based solely on a hemolyzed sample without clinical correlation - 98% of hemolyzed hyperkalemic samples in healthy children are pseudohyperkalemia 2
• Never administer potassium-containing fluids until confirmed potassium <5.5 mmol/L 3, 8
• Do not rely on furosemide as primary therapy in neonates - it is ineffective and potentially harmful in this population 7
• Do not delay exchange transfusion if severe hyperkalemia (>7 mmol/L) persists with ECG changes and hemodynamic instability 4

Target Potassium Range

Aim for serum potassium 4.0-5.5 mmol/L in neonates 3. Consider potassium >6.5 mmol/L or any level with ECG changes a medical emergency requiring immediate intervention 3.