Is a hemoglobin (Hgb) level of 20 considered high?

Is Hemoglobin 20 g/dL Considered High?

Yes, a hemoglobin level of 20 g/dL is definitely high and requires therapeutic intervention, particularly in patients with cyanotic congenital heart disease where phlebotomy is indicated when hemoglobin exceeds 20 g/dL and hematocrit is greater than 65% with associated hyperviscosity symptoms. 1

Understanding High Hemoglobin Levels

Normal Hemoglobin Ranges

• For adult males: 13.0-17.0 g/dL
• For adult females: 12.0-15.5 g/dL

A hemoglobin level of 20 g/dL significantly exceeds these normal ranges and represents a condition called polycythemia or erythrocytosis.

Causes of Elevated Hemoglobin

1. Congenital heart disease with cyanosis - Right-to-left shunting causes compensatory erythrocytosis 1
2. Polycythemia vera - A myeloproliferative disorder 2
3. Secondary polycythemia - Due to chronic hypoxemia (COPD, sleep apnea, high altitude)
4. Dehydration - Causes relative polycythemia

Clinical Implications and Management

When to Intervene

According to the American College of Cardiology/American Heart Association guidelines:

• Therapeutic phlebotomy is indicated when hemoglobin is greater than 20 g/dL and hematocrit exceeds 65% in patients who have symptoms of hyperviscosity (headache, dizziness, visual disturbances, fatigue) 1
• For patients with cyanotic congenital heart disease, phlebotomy is reasonable before non-cardiac surgery when hematocrit is >65% 1

Risks of High Hemoglobin

• Hyperviscosity syndrome - Impaired microcirculation
• Thrombotic events - Increased risk of stroke, myocardial infarction, and venous thromboembolism 3
• Higher mortality - The highest hemoglobin quartile shows increased risk for total mortality (HR = 1.48) and cardiovascular-related mortality (HR = 2.08) 3

Management Approach

For Patients with Cyanotic Congenital Heart Disease:

1. Therapeutic phlebotomy when:

   • Hemoglobin >20 g/dL AND
   • Hematocrit >65% AND
   • Patient has symptoms of hyperviscosity AND
   • No evidence of dehydration or anemia 1

2. Phlebotomy procedure:

   • Remove 1 unit of blood
   • Always replace with equal volume of dextrose or saline
   • Monitor for symptoms resolution 1

3. Avoid routine repeated phlebotomies as they can lead to:

   • Iron depletion
   • Decreased oxygen-carrying capacity
   • Increased risk of stroke 1

For Patients with Polycythemia Vera:

• Maintain hematocrit <45% through therapeutic phlebotomy 2
• Consider cytoreductive therapy for high-risk patients 2
• Low-dose aspirin for microvascular symptoms 2

Important Caveats

Avoid These Common Pitfalls:

1. Aggressive phlebotomy without adequate volume replacement can worsen symptoms
2. Ignoring iron status - Iron deficiency in the setting of high hemoglobin can lead to microcytosis and paradoxically increase blood viscosity 1
3. Failure to identify underlying cause - High hemoglobin requires investigation of the underlying etiology
4. Overtreatment - Not all patients with high hemoglobin require intervention; symptoms and clinical context matter

Special Considerations:

• In patients with chronic kidney disease, hemoglobin targets should generally be lower (11-12 g/dL) 1
• Women may require lower hematocrit targets (around 42%) in polycythemia vera 2
• Patients with methemoglobinemia may have falsely elevated hemoglobin readings 1

A hemoglobin of 20 g/dL requires careful evaluation and appropriate management based on the underlying cause, associated symptoms, and patient-specific factors to prevent serious complications related to hyperviscosity.