Case 21: Sickle Cell Disease

Question 1

Why do patients with sickle cell disease take hydroxyurea?

Answer 1

• Hydroxyurea often administered to reduce the number of sickle cell crises via its ability to increase circulating fetal hemoglobin, which in turn reduces the rate and extent of HbS sickling. Some other mechanisms include
  
  • reduced adhesion of erythrocytes to endothelial cells
  • reduced neutrophil activation
  • nitric oxide induced vasodilation

Question 2

What is pathophysiology of sickle cell disease?

Answer 2

• Hemoglobinopathy in which mutation of chromosome 11 results in substitution of valine for glutamic acid in beta chains of hemoglobin resulting in HbSS
• Presence of reduced O2 tension, HbS molecules polymerize, causing deformation of red cell membrtane into a sickled shape, leads to hemolysis
  
  • average RBC lifespan 20 days instead of 120 –> microvascular occlusion, inflammation, ischemic end organ injury

Question 3

What is aplastic crisis?

Answer 3

• Aplastic crisis results when bone marrow suppression 2/2 infection (parvovirus B19) or folate deficiency leads to decreased RBC production.
• Reduced production + reduced RBC lifespan in sickle cell disease results in profound anemia
  
  • High output heart failure
• Rx w/ correction of folate deficiency and admninstration of blood until bone marrow suppression resolves

Question 4

Describe the clasic Triad of Pre-eclampsia

Answer 4

PRE

• Proteinuria
• Rising Blood pressure
• Edema

Question 5

What steps can you take to reduce the risk of sickling in sickle cell patient?

Answer 5

• Maintain NORMOTHERMIA
• Avoid Hypotension and venous stasis
• Preserve oxygenation with supplemental O2
• Ensure adequate oxygen carrying capacity by transfusing PRBC as necessary
• Avoid acidosis which predisposes to hemoglobin deoxygenation

Question 6

Management of acute chest syndrome?

Answer 6

• Provide supplemental oxygen, bronchodilators, incentive spirometry, chest physiotherapy
• administer antibiotics
• ensure adequate pain control
• correct any anemia w/ blood transfusion
• consider exchange transfusion or mechanical ventilation

Question 7

Would you agree to using tourniquet in patient with sickle cell disease?

Answer 7

I would prefer to avoid tourniquet because of the regional stasis, acidosis, and deoxygenation of hemoglobin that occurs distal to the tourniquet. However since tourniquets have been utilized safely in sickle cell patients for up to 2 hours i would agree to this plan if it were necessary for the successful completion of the procedure. Considering the detrimental physiologic changes that occur distal to the tourniquet i would attempt to minimize tourniquet time.