What is the workup for hyperkalemia (elevated potassium level)?

Workup for Hyperkalemia

The workup for hyperkalemia should begin with immediate assessment of ECG changes and serum potassium level, followed by systematic evaluation of underlying causes and risk factors to guide appropriate management. 1

Initial Assessment

1. Laboratory Confirmation

• Verify true hyperkalemia with repeat testing to rule out pseudohyperkalemia (hemolysis, poor phlebotomy technique, fist clenching) 2
• Plasma K+ concentrations are typically 0.1-0.4 mEq/L lower than serum levels 2
• Classify severity:
  • Mild: >5.0 to <5.5 mEq/L
  • Moderate: 5.5 to 6.0 mEq/L
  • Severe: >6.0 mEq/L 2

2. Immediate ECG Evaluation

• Look for characteristic changes that progress with increasing potassium levels:
  • Peaked T waves (earliest sign)
  • Flattened or absent P waves
  • Prolonged PR interval
  • Widened QRS complex
  • Deepened S waves
  • Merging of S and T waves
  • Sine-wave pattern (severe cases) 2, 1

Caution: Normal or atypical ECG changes do not exclude the need for immediate intervention, as demonstrated in a prospective study where 25.4% of hyperkalemic patients had normal ECGs 3

Comprehensive Evaluation

1. Medical History

• Identify risk factors and potential causes:
  • Renal failure (most common cause) 2
  • Diabetes mellitus 2
  • Heart failure 2
  • History of previous hyperkalemia 2
  • Medications that impair potassium excretion:
    • RAAS inhibitors (ACE inhibitors, ARBs, MRAs)
    • Potassium-sparing diuretics
    • NSAIDs
    • Beta-blockers
    • Trimethoprim-sulfamethoxazole
    • Heparin
    • Calcineurin inhibitors 2, 1
  • Increased potassium intake:
    • Potassium supplements
    • Salt substitutes
    • Certain fruits (bananas, melons, orange juice) 2

2. Physical Examination

• Assess for:
  • Muscle weakness
  • Paresthesias
  • Cardiac symptoms (palpitations, chest pain)
  • Signs of underlying conditions (edema, hypertension) 1
  • Respiratory difficulties 2
  • Depressed deep tendon reflexes 2

3. Additional Laboratory Tests

• Complete metabolic panel:
  • BUN and creatinine (assess renal function)
  • Glucose (hyperglycemia can cause hyperkalemia)
  • Bicarbonate (assess acid-base status)
  • Calcium and magnesium levels 1
• Urinalysis and urine electrolytes
• Arterial blood gas (if metabolic acidosis suspected)
• Consider aldosterone and renin levels if primary hyperaldosteronism suspected

Diagnostic Algorithm

1. Confirm hyperkalemia with repeat testing if necessary
2. Assess ECG for cardiac manifestations
3. Determine severity based on potassium level and clinical presentation
4. Identify underlying cause:
   • Decreased renal excretion
   • Transcellular shift (acidosis, insulin deficiency)
   • Excessive intake
   • Medication-induced
   • Pseudohyperkalemia
5. Evaluate for end-organ damage (cardiac, neuromuscular)
6. Initiate appropriate management based on severity and clinical manifestations

Monitoring Recommendations

• For patients at risk (CKD, diabetes, HF, or on RAASi therapy):
  • Check K+ levels within 7-10 days after starting or increasing doses of RAASi therapy 2
  • Monitor more frequently in patients with increased hyperkalemia risk 2
  • Consider repetitive consecutive measurements to determine if hyperkalemia is chronic or transient 2

Common Pitfalls to Avoid

1. Failing to recognize pseudohyperkalemia
2. Relying solely on ECG findings (poor sensitivity for diagnosing hyperkalemia) 3
3. Ignoring mild or moderate hyperkalemia
4. Inadequate monitoring after initiating treatment
5. Overlooking medications as potential causes 1

By following this systematic approach to the workup of hyperkalemia, clinicians can quickly identify and address this potentially life-threatening electrolyte disorder while determining the appropriate management strategy based on severity and underlying causes.