Chapter 30: Sickle Cell Disease

Question 1

Identify the origin of SCD (2)

Answer 1

1. The abnormal hemoglobin, hemoglobin S, results from the substitution of valine for glutamic acid on the 𝞫-globin chain of hemoglobin.
2. Hgb S causes the RBC to stiffen and elongate, taking on a sickle shape in response to low O2 levels.

Question 2

Cite the characteristics of sickle cell disease. (5)

Answer 2

1. A group of inherited, autosomal recessive disorders characterized by an abnormal form of hemoglobin in the RB. 2.genetic disorder
2. SCD is usually found during routine neonatal screening.
3. median survival can now exceed 45 years old
4. disease often results in irreversible damage of the lungs, kidneys, brain, retina, or bones that significantly affects patients’ quality of life.

Question 3

Distinguish hemoglobin S (Hgb S) from the typical hemoglobin found on red blood cells.

Answer 3

They’re sickled instead of the regular donut-type shape. We already know that….

Question 4

Compare sickle cell anemia and sickle cell trait; identify which one is the more severe form of SCD

Answer 4

1. Sickle cell anemia is the most severe of the SCD syndromes. It occurs when a person is homozygous for hemoglobin S, meaning the person has inherited Hgb S from both parents.
2. Sickle cell trait occurs when a person is heterozygous for hemoglobin S. This means the person has inherited hemoglobin S from one parent and normal hemoglobin from the other parent. Sickle cell trait is typically a mild to asymptomatic condition.

Question 5

Describe a sickling episode and what might trigger an episode. (7)

type of event, what causes it, scenarios that lead to it, biggest 1

what happens when cells sickle, what do they cause

Answer 5

1. major pathophysiologic event of SCD is the sickling of RBCs.
2. Sickling episodes are most often triggered by low O2 tension in the blood.
3. Hypoxia or deoxygenation of the RBCs can be caused by viral or bacterial infection, high altitude, emotional or physical stress, surgery, and blood loss.
4. Infection is the most precipitating factor.
5. Other events that can trigger or sustain a sickling episode include dehydration, increased hydrogen ion concentration (acidosis), increased plasma osmolality, decreased plasma volume, and low body temperature.
6. A sickling episode can also occur without an obvious cause.
7. Sickle RBCs become rigid and take on an elongated, crescent shape.
8. Sickled cells cannot easily pass through capillaries or other small vessels and can cause vascular occlusion, leading to acute or chronic tissue injury.

Question 6

Describe a sickle cell crisis and symptoms associated with this crisis. (7)

Answer 6

1. Sickle cell crisis is a severe, painful, acute exacerbation of RBC sickling, causing a vaso-occlusive crisis.
2. As sickled cells impair blood flow, vasospasm occurs, further restricting blood flow. 3. Severe capillary hypoxia causes changes in membrane permeability, leading to plasma loss, hemoconcentration, thrombi, and further circulatory stagnation.
3. Tissue ischemia, infarction, and necrosis eventually occur from lack of O2.
4. Shock is a possible life-threatening consequence of sickle cell crisis because of severe O2 depletion of the tissues and a reduction of the circulating fluid volume.
5. Sickle cell crisis can begin suddenly and persist for days to weeks.

Question 7

Cite the reason for variable effects of SCD from person to person. (3)

Answer 7

1. The frequency, extent, and severity of sickling episodes are highly variable and unpredictable.
2. They depend on the percent of Hgb S present.
3. People with sickle cell anemia have the most severe form because the RBCs have a high percent of Hgb S.

Question 8

Discuss the main and accompanying symptoms associated with sickling RBCs. (10)

Answer 8

1. Grayish skin
2. Jaundice
3. Gallstones (cholelithiasis)
4. *PAIN (from trivial to excruciating)
5. Fever
6. Swelling
7. Tenderness
8. Tachypnea
9. HTN
10. N/V

Question 9

Describe complications associated with repetitive episodes of sickling.

Answer 9

*gradual involvement of spleen, lungs, kidney, and brain
*infection d/t spleen compromise (becomes smaller and more dysfunctional)
*pneumococcal pneumonia is most common infection
*aplastic crisis: causes RBCs to shut down
*hemolytic crisis
*gallstones
*Acute chest syndrome: pneumonia, tissue infarction, and fat embolism, fever, chest pain, cough, lung infiltrates, and dyspnea
*pulmonary infarctions -> pulmonary hypertension, MI, and cor pulmonale. The heart may become ischemic and enlarged, leading to HF
*retinal vessel obstruction -> hemorrhage, scarring, retinal detachment, and blindness
*Renal failure
*PE or strokes
*osteoporosis and osteosclerosis

Question 10

Review figure 30.4 on page 618 to understand long term systemic complications from sickling: brain 5

Answer 10

Thrombosis or hemorrhage causing paralysis, sensory deficits, death

Question 11

Review figure 30.4 on page 618 to understand long term systemic complications from sickling: eyes 4

Answer 11

Hemorrhage
Retinal detachment
Blindness
Retinopathy

Question 12

Review figure 30.4 on page 618 to understand long term systemic complications from sickling: lungs 3

Answer 12

Acute chest syndrome
Pulmonary hypertension
Pneumonia

Question 13

Review figure 30.4 on page 618 to understand long term systemic complications from sickling: heart 1

Answer 13

HF

Question 14

Review figure 30.4 on page 618 to understand long term systemic complications from sickling: liver and gallbladder 2

Answer 14

Hepatomegaly
Gallstones

Question 15

Review figure 30.4 on page 618 to understand long term systemic complications from sickling: spleen 1

Answer 15

Splenic atrophy (autosplenectomy)

Question 16

Review figure 30.4 on page 618 to understand long term systemic complications from sickling: kidney 2

Answer 16

Hematuria
Renal failure

Question 17

Review figure 30.4 on page 618 to understand long term systemic complications from sickling: bones and joints 2

Answer 17

Hand-foot syndrome
Osteonecrosis

Question 18

Review figure 30.4 on page 618 to understand long term systemic complications from sickling: penis 1

Answer 18

Priapism

Question 19

Review figure 30.4 on page 618 to understand long term systemic complications from sickling: skin 1

Answer 19

Stasis ulcers of hands, ankles, and feet

Question 20

Describe the characteristics of hemolysis which occurs due to RBC breakdown. 4

Answer 20

*Physical destruction of RBCs results from the exertion of extreme force on the cells.
*Traumatic events causing disruption of the RBC membrane include hemodialysis, extracorporeal circulation used in cardiopulmonary bypass, and prosthetic heart valves.
*the force needed to push blood through abnormal vessels, such as those that have been burned, irradiated, or affected by vascular disease may physically damage RBCs.
*RBCs can be fragmented and destroyed as they try to pass through abnormal arterial or venous microcirculation.

Question 21

Describe the priorities of care for patients experiencing a sickle cell crisis. 9

Answer 21

*may need hospitalized
*o2 therapy treats hypoxia
*Assess for any changes in respiratory status and encourage incentive spirometry
*rest
*DVT prophylaxis (anticoagulants) should be prescribed
*fluids to reduce blood viscosity
*Priapism is managed with pain medication, fluids, and nifedipine
*transfusion therapy
*iron chelation therapy

Question 22

Speculate on the reasons for undertreatment of sickle cell pain. 2

Answer 22

*Lack of understanding can lead HCPs to underestimate the severity of acute and chronic pain
*SCD patients may develop tolerance, and larger doses of pain medication may be needed to reduce pain to a tolerable level

Question 23

Identify one of the most frequent complications of sickle cell disease.

Answer 23

Infection is a frequent complication (especially chronic leg ulcers)

Question 24

Review the action of hydroxyurea on SCD. 3

Answer 24

*Hydrea is the only med that is clinically beneficial.
*This drug increases the production of hemoglobin F (fetal hemoglobin) and alters the adhesion of sickle RBCs to the endothelium.
*The increase in Hgb F is accompanied by a reduction in hemolysis, an increase in hemoglobin concentration, and a decrease in sickle cells and painful crises.

Question 25

Describe how 2 dietary supplements, folic acid and glutamine, could help a patient with SCD.

Answer 25

*Dietary supplementation with oral glutamine can reduce the number and frequency of pain crises and hospitalizations.
*Because chronic hemolysis results in increased use of folic acid stores, the patient should take an oral folic acid supplement.

Question 26

Describe patient teaching and support needed for long-term management of SCD. 6

Answer 26

*Teach the patient ways to avoid crises.
*Review steps to avoid dehydration and hypoxia, such as avoiding high altitudes and seeking medical attention quickly to counteract problems such as upper respiratory tract infections.
*Teach patients to maintain adequate fluid intake. Immunizations, such as pneumococcal, H. influenzae, influenza, and hepatitis, should be given.
*Screening for retinopathy should begin at age 10.
*Each person with SCD should have a reproductive life plan.
*Teaching about pain control is needed because the pain during a crisis may be severe and often requires considerable analgesia.