Flashcards in Case 30 Deck (47):
What are key findings from history in a 2 yr old with sickle cell disease and acute chest syndrome?
What are key findings from physical exam in a 2 yr old with sickle cell disease and acute chest syndrome?
-Tachypnea with rhonchi
-Decreased breath sounds
What is on the differential diagnosis for acute chest syndrome?
Sepsis, Rib infarction, congestive heart failure, pericarditis
What are key findings from testing in a child with acute chest syndrome?
New infiltrates on chest Xray, Cardiomegaly, Leukocytosis.
Pathophysiology of Sickle Cell Disease (SCD):
-Substitution of valine for glutamic acid at the sixth amino acid position of the hemoglobin molecule
-This abnormal hemoglobin polymerizes when deoxygenated
-Polymers then deform the RBC into characteristic sickle cells
-Sickle cells have increased adherence and block blood flow in the microvasculature
-Result: Local tissue hypoxia, pain, and tissue damage
-The abnormal hemoglobin also induces hemolysis of the RBCs leading to chronic anemia and elevation of the reticulocyte count
What is the inheritance of sickle cell disease?
-Gene mutation frequency 7-10 percent among african americans living in the US
-Sickle cell trait is also seen in the Hispanic population but with a lower gene frequency.
--Normal gene (A)
--Sickle hemoglobin gene (S)
--If both parents have one copy of the sickle cell gene (S), then:
25percent of offspring could have sickle cell disease (SS)
25percent are expected to have normal AA globin
50percent are expected to have sickle cell trait (AS)
Evaluating pain in patient with sickle cell disease:
-A scale that shows faces (in stages from happy to crying) is validated for children ages 4 and up.
-Children with SCD who have frequent pain crises sometimes understand the faces scale earlier than age 4 (even as young as 2)
-Sometimes, even children over 4 years are too ill to comply with the request. In this case, parental judgement is best tool for assessing child's pain.
Physical Exam for child with SCD - General:
Growth impairment common in children with SCD due to chronic anemia, poor nutrition, painful crises, endocrine dysfunction, and/or poor pulmonary dysfunction.
Physical Exam for child with SCD - HEENT:
Observe sclera for signs of icterus (clue to the degree of RBC hemolysis)
Physical Exam for child with SCD - CV:
Flow murmur common in SCD.
Physical Exam for child with SCD - Abdomen:
-Enlargement of spleen is common during first few years of life in children with SCD
-Massive enlargement or rapid change in spleen size can indicate sepsis or splenic sequestration crisis (life-threatening complication that occurs when blood pools in the spleen, leading to severe anemia and shock)
-Routine assessment of the spleen size by the parents can lead to earlier detection and treatment
-Spleen becomes progressively fibrotic and by the time the child is four to six years old, is no longer palpable.
-Children with hemoglobin SC or S beta thalassemia can have splenic enlargement into adolescence
Physical Exam for child with SCD - Neurologic:
Evaluate for potential stroke.
What is on the differential diagnosis for acute chest syndrome?
Sepsis, Rib infarction, Congestive heart failure, pericarditis.
Acute Chest Syndrome:
-One of the most common causes of death in patients with SCD
-Clinical features: Fever, cough, chest pain, shortness of breath, and decreased oxygenation
-CXR findings: Multilobar infiltrates (more commonly lower and middle lobes), effusions, and atelectasis.
-Difficult to discern if lung infiltrate due to infection, pneumonia, or atelectasis
-Decreased splenic function in SCD leads to decreased resistance to infection with encapsulated organisms (Strep pneumo., Haemophilus influenzae type b, Neisseria meningitidis).
-New infiltrates would not be a usual finding unless the sepsis leads to acquired/adult respiratory distress syndrome (ARDS)
Always consider when child with SCD presents with chest pain (could be vaso-occlusive crisis)
Congestive heart failure:
-Can occur in patients with SCD and chronic anemia
-Tachypnea is common sign of CHF in children
-Usually does not cause chest pain on its own
-Uncommon cause of chest pain
--Presents with tachypnea and fever
--Can present with effusion and infiltrate
Newborn screening for SCD:
-Knowing a newborn's screening results is important, because beginning penicillin prophylaxis as soon as possible (definitely by two months of age) is vital in preventing pneumococcal sepsis.
-Universal screening for inherited blood cell disorders now occurs in virtually all of the states and in the District of Columbia
Nomenclature seen on the newborn screen:
-At birth, the predominant hemoglobin is hemoglobin F (fetal)
-Normal adult hemoglobin is hemoglobin A
-Hemoglobin F is always listed first, followed by other hemoglobins listed in order of concentration:
--FS would be the most common hemoglobin pattern when looking for sickle cell disease
--When one of the globin genes has a mutation for S and the other has a mutation for thalassemia (i.e., produces little or no normal hemoglobin) you may see patterns such as FSA (S-beta thalassemia +) or FS (S-beta thalassemia 0), both of which are sickling disorders.
--When one gene has the S mutation and one gene has the mutation for hemoglobin C, then the pattern is FSC.
Most common hemoglobin pattern for sickle cell disease
FSA or FS
One globin gene has a mutation for S, and the other has a mutation for thalassemia, producing sickling disorders of a milder phenotype
One gene has the S mutation and the other has the mutation for hemoglobin C
Prenatal diagnosis of SCD:
-Sample fetal blood obtained in utero
-DNA extraction from chorionic villi
-Hgb, hematocrit, and reticulocyte count can be interpreted only in relation to prior values and whether or not the child has had recent transfusion therapy.
-Baseline Hgb for children with sickle cell is often between 6 and 9 mg/dL.
-Although there is accommodation to the chronic anemia, the lower the baseline hemoglobin, the more difficult it is for the patient to withstand any acute change
-Patients with SCD frequently demonstrate an exaggerated leukocytosis and thrombocytosis in response to stress; CBC findings do not usually definitely help to identify pneumonia or which of the ACS causes is present.
Study of intracranial blood-vessel flow to assess risk of stroke
Chronic issues in SCD:
Anemia can cause chronic fatigue; will be more severe due to myelosuppression from infections such as Parvovirus or from hypersplenism (when spleen enlarges and traps blood cells)
What are signs of medical emergencies in SCD:
-Tachypnea, chest pain, cough
Fever in SCD:
May be the only sign of serious infection
Slurred speech in SCD:
--10 percent of children with SCD will have a stroke by age 15
--An exchange transfusion may be indicated to lower the hemoglobin-S level and prevent progression or recurrence
Tachypnea, chest pain, cough in SCD:
Lungs are a site of sickling problems.
-Acute chest syndrome (ACS)
--May be result of infectious process, intrapulmonary sickling or pulmonary fat embolism (all appear similar on CXR)
--Requires supplemental oxygen and transfusion therapy
Increased jaundice in SCD:
-Baseline jaundice typical in SCD and not an emergency
-Marked increase in the level of jaundice, however, may indicate an increase in the degree of hemolysis and a need for transfusion (may be associated with a viral illness)
Increased pallor in SCD:
-Baseline pallor is a typical finding from the anemia of SCD and does not constitute an emergency
-Increased pallor, however, can be due to splenic sequestration, increased hemolysis, or a temporary inhibition of erythroid production (aplastic crisis)
Priapism in SCD:
Sickling in the penile arteries can cause permanent damage.
Prevention of complications in SCD:
1. Antibiotic prophylaxis
Antibiotic Prophylaxis for SCD:
-Due to decreased splenic function and consequent decreased resistance to infection with encapsulated organisms (Strep pneumo., H. influenzae type b, Neisseria meningitides), infants and young children with SCD are at increased risk for sepsis
-When given to infants with sickling disorders, penicillin significantly decreases the risk of mortality from overwhelming sepsis.
-Prophylaxis is usually continued until the child is five or six years of age (after this, little data to support its use except in patients who have had documented sepsis and bacteremia, or who have had their spleens removed).
Immunization for SCD:
-Hemophilus influenza type B conjugate vaccine and 13-valent pneumococcal conjugate vaccine (Preener 13) given at two, four and six months
-To expand antibody coverage beyond the 13 initial serotypes, children with sickling disorders also receive the 23-valent pneumococcal polysaccharide vaccine at two years of age, with a repeat dose three to five years later.
-The meningococcal conjugate vaccine is also given at age two years to children with functional asplenia (most children with SCD), with a booster dose three to five years later
-Annual influenza vaccine
Complications of SCD:
1. Acute Chest Syndrome (ACS)
3. Waldeyer's ring lymphoidal-tissue hypertrophy
4. Bilirubin gallstones
Management of Pain in Acute Chest Syndrome:
-Can decrease the ability to fully expand the lungs
-Narcotic analgesia relieves the pain and improves ability to take a deep breath
-Narcotics are respiratory depressants, however, and therapeutic balance must be carefully maintained
Management of Hydration in Acute Chest Syndrome:
-IV infusion because respiratory distress and tachypnea both increase fluid demands and make it difficult for the child to tolerate oral liquids
-Correct dehydration, provide replacement for insensible losses (increased with fever and tachypnea), and give maintenance fluids
-1.5 times normal maintenance because dehydration may contribute to intracellular hemoglobin polymerization and RBC sickling
-With ACS, avoid hydrating too vigorously and causing pulmonary edema from volume overload
Management of Incentive Spirometry in Acute chest syndrome:
-Encourage deep breathing to avoid atelectasis
Management of Antibiotics in acute chest syndrome:
-Practice guidelines and clinical data support the use of antibiotics in ACS
-Infectious agents causing ACS include: Viruses, chlamydia, mycoplasma, and bacteria.
-Effective antibiotic choices depend on local patterns of antimicrobial resistance
Transfusion of packed RBCs in acute chest syndrome if:
-Hemoglobin below baseline
-Increasing respiratory rate or chest symptoms
-Declining oxygen saturation
Exchange transfusion or erythrocytapheresis in Acute Chest Syndrome:
Reserve for especially severe disease and/or hypoxemia not corrected by oxygen therapy.
Sepsis in SCD:
-Fever may be the only sign of sepsis in children with sickle cell disease and must be dealt with as a medical emergency, with rapid evaluation, blood cultures and institution of broad spectrum parenteral antibiotics while waiting for culture results to guide therapy.
-Children with sickle cell disease also get "normal" colds and other viral illnesses.
-Lack of normal spleen function as well as other more subtle immunologic deficiencies call for a rapid and aggressive approach.
Waldeyer's Ring Lymphoidal-tissue hypertrophy in SCD:
-Common in children with SCD, evidenced by:
--Obstructive sleep apnea
-Treatment: Tonsillectomy with adenoidectomy