How do you manage abnormal hematocrit (Hct) levels?

Management of Abnormal Hematocrit Levels

Single hematocrit measurements should not be used as an isolated laboratory marker for bleeding, but rather serial measurements along with clinical assessment and other laboratory parameters should guide management of abnormal hematocrit levels. 1

Diagnostic Approach to Abnormal Hematocrit

Normal Reference Ranges

• Adult males/post-menopausal females: Hb 15.5 ± 2.0 g/dL and Hct 47 ± 6%
• Menstruating females: Hb 14.0 ± 2.0 g/dL and Hct 41 ± 5% 2

Initial Assessment

• Evaluate for symptoms of anemia or polycythemia
• Assess for potential causes (blood loss, fluid shifts, chronic disease)
• Check additional laboratory parameters:
  • Complete blood count
  • Serum lactate and base deficit (sensitive markers for bleeding and shock) 1
  • Iron studies if anemia is present

Management of Low Hematocrit (Anemia)

Transfusion Thresholds

• For critically ill patients: Transfuse when hemoglobin <7.0 g/dL, targeting 7.0-9.0 g/dL 2
• Higher thresholds (Hb <8 g/dL) may be appropriate for:
  • Patients with cardiac disease
  • Perioperative patients
  • Patients with symptomatic anemia

Iron Supplementation

• Indicated when iron deficiency is confirmed
• Maintain transferrin saturation >20%
• IV iron preferred in hemodialysis patients 2

Erythropoiesis-Stimulating Agents (ESAs)

• Consider in chronic kidney disease
• Target hemoglobin of 10-11.5 g/dL
• Avoid in critical illness 2

Monitoring

• Check hemoglobin after 2-4 weeks of therapy
• Expected rise: 1-2 g/dL within 3-4 weeks 2

Management of High Hematocrit (Polycythemia)

Primary Polycythemia (Polycythemia Vera)

• Phlebotomy is the primary treatment
• Target hematocrit:
  • Men: <45%
  • Women: <42% 2
• Phlebotomy regimen: 300-450 ml of blood withdrawn weekly or twice weekly until target hematocrit is reached 2
• Low-dose aspirin (81-100 mg daily) recommended to reduce thrombotic risk 2
• Cytoreductive therapy for high-risk patients or those with poor tolerance to phlebotomy 2

Secondary Polycythemia

• Address underlying cause (hypoxemia, smoking, high altitude)
• For patients with cyanotic heart disease:
  • More conservative approach with target hematocrit of approximately 60%
  • Avoid aggressive phlebotomy due to risk of stroke 2
  • Phlebotomy only if symptomatic (headache, poor concentration) 1

Monitoring

• Regular follow-up every 3-6 months with CBC and symptom assessment
• Monitor for complications: iron deficiency, thrombosis, bleeding 2

Special Considerations

Trauma Patients

• Hematocrit has low sensitivity (0.5) for detecting traumatic hemorrhage requiring surgical intervention 1
• Decreasing serial hematocrit measurements may reflect continued bleeding, but a patient with significant bleeding may maintain stable serial hematocrit due to fluid shifts 1
• Use serum lactate and base deficit as more sensitive markers for bleeding and shock 1

Surgical Patients

• Patients with PAH are highly sensitive to reductions in hemoglobin levels
• Promptly treat any mild anemia 1
• For patients with long-standing hypoxia and right-to-left shunts:
  • Consider phlebotomy if hematocrit >65% and patient is symptomatic 1

Hemochromatosis

• Phlebotomy is the primary treatment
• One phlebotomy (removal of 500 mL of blood) weekly or biweekly
• Check hematocrit prior to each phlebotomy; allow hematocrit to fall by no more than 20% of prior level
• Check serum ferritin level every 10-12 phlebotomies
• Stop frequent phlebotomy when serum ferritin falls below 50 ng/mL 1

Common Pitfalls to Avoid

1. Relying solely on single hematocrit measurements: Serial measurements provide more valuable information about ongoing bleeding 1

2. Ignoring the effects of fluid resuscitation: IV fluids can dilute hematocrit, masking ongoing bleeding 1

3. Aggressive phlebotomy in secondary polycythemia: Can lead to iron deficiency and increased stroke risk in patients with cyanotic heart disease 1, 2

4. Targeting normal hematocrit in all conditions: Different conditions require different target ranges 2

5. Overlooking the need for supplemental vitamin C restriction: Patients receiving iron chelators should not exceed 200 mg of vitamin C intake daily 1