Management of Elevated Hemoglobin and Red Blood Cell Counts in Children
The primary approach to elevated hemoglobin and RBC counts in children depends entirely on the underlying cause: for secondary polycythemia, treat the underlying condition; for primary polycythemia (extremely rare in children), cytoreduction with hydroxyurea is indicated when symptomatic or at risk for thrombotic complications.
Initial Diagnostic Approach
The first critical step is distinguishing between primary (clonal) and secondary (reactive) causes of elevated hemoglobin:
- Obtain a complete blood count with differential to assess the degree of elevation and evaluate other cell lines 1
- Assess for symptoms of hyperviscosity: headache, dizziness, visual disturbances, or thrombotic events 2
- Evaluate for underlying conditions causing secondary polycythemia: chronic hypoxemia (cyanotic heart disease, chronic lung disease), renal disorders, or inappropriate erythropoietin production 3
- Consider age and sex-specific normal ranges, as hemoglobin values vary significantly with age in children 2
Management Based on Etiology
Secondary (Reactive) Polycythemia
Address the underlying cause rather than the elevated hemoglobin itself:
- For chronic hypoxemia: optimize treatment of cardiac or pulmonary disease 3
- For dehydration-related hemoconcentration: provide adequate hydration 2
- Monitor hemoglobin levels after treating the underlying condition to confirm normalization 1
Primary Polycythemia (Myeloproliferative Disorder)
This is exceedingly rare in children (incidence of 1 per million), but when present requires aggressive management 4:
Cytoreduction with hydroxyurea is the primary treatment:
- Initial dosing: 25-50 mg/kg/day in 2-3 divided doses 2
- Monitor blood counts at least weekly during therapy 5
- Adjust dose based on response, with goal of normalizing blood counts while avoiding myelosuppression 5
- Severe anemia must be corrected before initiating hydroxyurea 5
For patients with renal impairment:
- Reduce hydroxyurea dose by 50% if creatinine clearance is <60 mL/min 5
Management of Acute Complications
Hyperviscosity Syndrome with Leukostasis
When elevated RBC/hemoglobin causes symptomatic hyperviscosity:
- Initiate intravenous hydration (2.5-3 liters/m²/day) titrated to clinical status 2
- Start hydroxyurea immediately at 25-50 mg/kg/day for cytoreduction 2
- Consider leukapheresis or exchange transfusion for emergency organ-threatening conditions (cerebral symptoms, pulmonary compromise) - these procedures can achieve 30-80% reduction within hours 2
Thrombotic Complications
- Ensure adequate hydration to reduce blood viscosity 2
- Avoid low-dose aspirin in young children due to risk of Reye syndrome and platelet dysfunction 2
- Aggressive cytoreduction with hydroxyurea is indicated 2
Critical Monitoring Parameters
During hydroxyurea therapy, monitor for:
- Myelosuppression: leukopenia is the first and most common manifestation; thrombocytopenia and anemia occur less frequently 5
- Hemolytic anemia: evaluate for jaundice, hematuria, elevated LDH, low haptoglobin, and positive Coombs test; discontinue hydroxyurea if confirmed 5
- Macrocytosis: self-limiting and often seen early in treatment; prophylactic folic acid is recommended 5
Important Caveats and Pitfalls
Common pitfalls to avoid:
- Do not treat elevated hemoglobin in chronic kidney disease patients above 13.0 g/dL with erythropoiesis-stimulating agents, as this increases cardiovascular risk including myocardial events and stroke 2
- Do not initiate hydroxyurea if bone marrow function is markedly depressed 5
- Avoid live vaccines in patients receiving hydroxyurea, as it may potentiate viral replication and increase adverse vaccine reactions 5
- Do not confuse physiologic variations in hemoglobin (which vary by age and sex) with pathologic polycythemia 2
Special considerations:
- Hydroxyurea is teratogenic: females of reproductive potential should use effective contraception during and for 6 months after therapy; males should use contraception during and for 1 year after therapy 5
- Hydroxyurea is a human carcinogen: monitor for secondary malignancies and advise sun protection 5
- Consultation with pediatric hematology is essential for persistent, unexplained, or symptomatic elevations 4