Sickle Cell

Question 1

When do the HbS RBC change shape? What shape do they become?

Answer 1

When they are deoxygenated, they produce rigid needle or spindle shapes in the RBC.

Sickle every time they give up O2 in microcirculation

Question 2

What is the lifespan of HbS RBC? Why is it reduced?

Answer 2

10-15 days. Reduced because constant cycling between shapes damages the channels or pumps on its membrane. Then it becomes permanently sickled.

Question 3

How are majority of HbS RBC destroyed?

Answer 3

Extravascularly by the spleen.

Question 4

Trigger factors for vaso-occlusive events?

Answer 4

O2
Dehydrated
Acidosis
Temp (cold)
Infection
Vigour exercise
Menorrhagia

Question 5

Treatment for SS cell disease?

Answer 5

Hydroxyurea to increase levels of HbF.

Question 6

What is the most important factor that modifies the severity of SS cell disease?

Answer 6

Levels of HbF.

Question 7

List the main clinical manifestations of sickle cell disease

Answer 7

1. Anaemia (6.0-10)
2. Clinically detectable jaundice (due to chronic haemolysis)
3. Infection - increase risk of infection by encapsulated organisms. (pneumococcus, Haemophilus Influenza)
4. Increased risk of osteomyelitis (salmonella)
5. Painful crisis - due to vaso-occlusive crisis

Question 8

Features of vaso-occlusive crisis

Answer 8

Pain affecting many organs (mostly bones in spine & limbs)
Sausage fingers & toes (dactylitis)
Acute chest syndrome
Avascular necrosis of the femoral head
Pain many organs (varying with frequency & severity)

Question 9

Whats acute chest syndrome?

Answer 9

Complication of vaso-occlusive crisis. 3 things:

• Chest pain
• SOB
• Lung infiltrates.

Question 10

Tx for acute chest syndrome?

Answer 10

Mechanical ventilation & emergency transfusion if severe hypoxia

Question 11

Mx of vaso-occlusive crisis?

Answer 11

O2, if hypoxia
Fluids (oral or IV)
opiate analgesia
Broad spec Abx
Blood transfusion (if acute chest syndrome)

Question 12

Causes of acute anaemia (sudden drop in Hb)

Answer 12

Haemolytic crisis - sometimes associated with infection
Aplastic crisis - decrease in reticulocyte. BM stop production

Sequestration crisis - vaso-occlusion of spleen. cause pooling of RBC

Question 13

Consequences of sequestration crisis

Answer 13

1. Hepatosplenomegaly
2. Abdo pain
3. Circulatory collapse

Then get atrophy + fibrosis, then autosplenectomy

Question 14

Acute complications of sickle cell anaemia?

Answer 14

1. Asplastic crisis - Hb falls very low. <1.5 Parv