Does elevated hemoglobin (Hb) and hematocrit (Hct) increase the risk of complications during surgery?

Elevated Hemoglobin and Hematocrit Increase Surgical Risk

Elevated hemoglobin (Hb) and hematocrit (Hct) levels, particularly when Hct exceeds 51%, are associated with an increased risk of 30-day postoperative mortality and cardiac events in patients undergoing surgery. 1

Risks Associated with Elevated Hb/Hct

• Polycythemia, thrombocytosis, and other conditions that increase blood viscosity and hypercoagulability may increase the risk of thromboembolism or hemorrhage during surgical procedures 1
• The adjusted risk of 30-day postoperative mortality and cardiac morbidity begins to rise when hematocrit levels exceed 51% in patients undergoing major noncardiac surgery 1
• Elevated Hb/Hct can lead to increased blood viscosity, which increases flow resistance and may compromise tissue perfusion, particularly in patients with cardiovascular disease 2
• Red blood cell transfusions and resulting rapid increases in Hb/Hct have been associated with increased risks of venous thromboembolism (odds ratio 1.60) and arterial thromboembolism (odds ratio 1.53) 3

Specific Surgical Considerations

• In patients with cyanotic congenital heart disease, therapeutic phlebotomy is indicated when hemoglobin exceeds 20 g/dL and hematocrit exceeds 65%, particularly when associated with symptoms of hyperviscosity 1
• However, repeated routine phlebotomies are not recommended due to the risk of iron depletion, decreased oxygen-carrying capacity, and stroke 1
• Patients with elevated Hb/Hct may have hemostatic abnormalities that can increase bleeding risk during surgery, making the use of anticoagulants and antiplatelet agents controversial 1
• For patients with elevated Hb/Hct undergoing surgery, appropriate steps to reduce thromboembolism and hemorrhage risks should be tailored to the individual patient's circumstances 1

Management Approach for Patients with Elevated Hb/Hct Requiring Surgery

1. Preoperative Assessment:

   • Determine if the elevation represents true polycythemia (actual increase in red cell mass) or apparent polycythemia (decreased plasma volume) 3
   • For true polycythemia, distinguish between primary polycythemia vera (clonal disorder) and secondary polycythemia (often EPO-mediated) 3
   • Assess for symptoms of hyperviscosity (headache, increasing fatigue) 1

2. Risk Stratification:

   • Patients with cardiovascular disease and elevated Hb/Hct are at particularly high risk for adverse outcomes 1
   • Consider the type of surgery and expected blood loss - mortality in elective surgery appears to depend more on estimated blood loss than on preoperative hemoglobin levels 4

3. Preoperative Management:

   • For patients with Hb >20 g/dL and Hct >65% with symptoms of hyperviscosity, therapeutic phlebotomy may be indicated prior to surgery 1
   • Ensure adequate hydration to prevent further increases in blood viscosity 2
   • Consider consultation with a hematologist for patients with significantly elevated values 3

Special Considerations

• The optimal Hct for oxygen transport may be different in health versus disease states 2
• In patients with cardiovascular disease, even mild polycythemia can significantly increase perioperative risk 1
• The presence of other risk factors (such as advanced age, renal insufficiency, or diabetes) may compound the risks associated with elevated Hb/Hct 1

Monitoring Recommendations

• Careful intraoperative monitoring of fluid status is essential to prevent further increases in Hb/Hct due to dehydration 3
• Monitor for signs of thrombotic complications, particularly in patients with cardiovascular disease 1
• Point-of-care Hb/Hct testing during surgery may have limitations and biases that should be considered when making clinical decisions 5

Remember that while elevated Hb/Hct poses risks, anemia also increases perioperative complications, with the adjusted risk of 30-day postoperative mortality and cardiac morbidity beginning to rise when hematocrit levels decrease to less than 39% 1. The goal should be to achieve optimal Hb/Hct levels that balance oxygen-carrying capacity against the risks of increased blood viscosity.