sickle cell disease core concepts for the emergency p hysician and nurse
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Sickle Cell Disease Core Concepts for the Emergency P hysician and Nurse. Epidemiology, Genetics, Pathophysiology Spring 2013 Paula Tanabe, PhD, RN, FAEN, FAAN Associate Professor Duke University, Schools of Nursing and Medicine. Epidemiology of SCD. - PowerPoint PPT PresentationTRANSCRIPT
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Sickle Cell DiseaseCore Concepts for the
Emergency Physician and Nurse
Epidemiology, Genetics, PathophysiologySpring 2013
Paula Tanabe, PhD, RN, FAEN, FAANAssociate Professor
Duke University, Schools of Nursing and Medicine
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Epidemiology of SCD
• SCD is a genetic disease affecting 70,000 – 100,000 Americans, primarily of African descent (Hassell, 2010)
• Most common genetic disease among blacks
• SCD occurs in 1 of every 500 black births• 1:1,100 Hispanics (eastern states) • 1:32,000 Hispanics (western states)• SCD occurs in many other ethnic groups, including
Northern Europeans and those that live in the Middle Eastern Countries
• 1:12 African-Americans are carriers (trait) for the disorder
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Comparison of Life ExpectancyUS Population vs. Sickle Cell Disease
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Changes in Life Expectancy
• National Center for Health Statistics (CDC)
• Compared 1999-2007 with 1979-1998
• Largest declines in ages 0-4
• Smaller but significant declines up to age 19
– Due to prophylactic treatment with penicillin and vaccinations
– Transcranial doppler screening identifies children at risk of stroke; placed on chronic transfusion therapy to prevent stroke
• No differences in the 20-24 age group
• Increase in death rate ages: 45-54, 55-65, and 65-75
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What is the pathophysiology?
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Normal Vs. Sickle Red CellsNormal
• Biconcave disc-shaped• Deformable• Life span of 120 days
Sickle• Sickle-shaped• Rigid • Live for 20 days or
less• Sticky surface,
abnormal properties
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Prolonged Sickling of RBC’s
• After recurrent episodes of sickling–membrane damage
occurs– cells not capable of
resuming biconcave shape upon re-oxygenation
• Deformed sickle cells adhere to endothelium & macrophages– induces hemolytic
process
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Hemolysis and Vaso-occlusion
Vaso-occlusion:• Complex process initiated
by rigid and abnormally shaped sickled RBC’s
• Abnormal adhesion occurs to the endothelium
• Activation of WBC’s, RBC’s and the endothelial surface which enhances the VOC process
• Results in tissue damage, hypoxia, necrosis and organ dysfunction
Hemolysis:▪ Anemia in SCD is caused by red cell destruction, or hemolysis
▪ The degree of anemia varies widely between patients
▪ Red cell production by the bone marrow increases dramatically, but is unable to keep pace with the destruction
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Chronic Manifestations:• Anemia• Jaundice• Splenomegaly• Functional asplenia• Cardiomegaly and functional
murmurs• Hyposthenuria and enuresis• Proteinemia• Cholelithiasis• Delayed growth and sexual
maturation• Restrictive lung disease*• Pulmonary hypertension*• Avascular necrosis• Proliferative retinopathy• Leg ulcers• Transfusional hemosiderosis*
Acute Manifestations:• Bacterial sepsis or
meningitis*• Recurrent vaso-occlusive
pain (dactylitis, musculo-skeletal or abdominal pain)
• Splenic sequestration*• Aplastic crisis*• Acute chest syndrome*• Stroke*• Priapism• Hematuria, including
papillary necrosis
Acute and Chronic Manifestations
*Potential cause of mortality
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Sickle Cell Disease (SCD) Common Genotypes
Sickle cell anemia (SS, most severe form)
Sickle/Hb C disease (SC, lesser severity, but can still have pain episodes, and life-threatening complications)
Sickle/Beta plus thalassemia (Sβ+ thalassemia, similar to SC)
Sickle/Beta zero thalassemia(Sβ° thalassemia, similar to SS)
65 %
25 %
8 %
2 %
Genotype Approximate % of US Patients
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References• Hassell KL. Population estimates of sickle cell disease in
the U.S. Am J Prev Med. 2010;38(4S):S512-S521.
• Platt et al. Mortality in sickle cell disease, life expectancy and risk factors for early death. NEJM 1994. 330: 1639-44.
• Hamideh, D. Trends in Mortality Among Patients with SCD in the United States. Is there any change in the past 10 years? 2012. 6th Annual Sickle Cell Disease Research and Educational Symposium & Annual National SCD Scientific Meeting
• http://wonder.cdc.gov/controller/datarequest/D79
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Post-Test
1. Which genotype is associated with the most severe symptoms?
a) SSb) SCc) SB0
d) SB+
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Post-Test
2. What is the median lifespan for most individuals with SCD?a) 20’sb) 30’sc) 40’sd) 50’s
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Post Test Answers
1. A – Patients with SS have the most severe form of the disease which is associated with more complications. However, all patients can experience pain and multiple other complications.
2. C – The median lifespan continues to be 48 for females and 42 for males.