30: 2-year-old male with sickle cell disease Flashcards
Pathophysiology of Sickle Cell Disease (SCD)
- -SCD is a group of disorders characterized by substitution of valine for glutamic acid at the sixth amino acid position of the hemoglobin molecule.
- -This mutation leads to the formation of polymers of hemoglobin when the hemoglobin becomes deoxygenated.
- -These polymers lead to deformation of the rbc into the characteristic “sickle” cells. Sickle cells have increased adherence and block blood flow in the microvasculature, which leads to local tissue hypoxia, pain, and tissue damage.
- -The abnormal hgb induces hemolysis of the rbc leading to chronic anemia with an elevation of the retic count.
F
Predominant hemoglobin at birth is hemoglobin F (fetal), so this always appears first in the naming.
A
Hemoglobin A is normal adult hemoglobin.
FS
FS is the most common hemoglobin pattern causing sickle cell disease.
FSA
- -FSA is sickle cell beta thalassemia, meaning one of the globin genes has a mutation for S and the other has a mutation for beta thalassemia (which produces no or little normal hemoglobin).
- -This pattern causes a sickling disorder, although it may behave in a milder fashion than FS (in which both genes have the sickling mutation). From a clinical management standpoint, these patients are treated in the same manner.
FSC
- -FSC is sickle cell hemoglobin C disease: one gene has the S mutation and one gene has the mutation for hemoglobin C.
- -This pattern causes a sickling disorder, although it may behave in a milder fashion than FS (in which both genes have the sickling mutation). From a clinical management standpoint, these patients are treated in the same manner.
Common Procedures for Young Individuals with SCD: TONSILLECTOMY
Lymphoidal-tissue hypertrophy involving Waldeyer’s ring is common in children with sickle cell disease.
- -Excessive snoring may be observed, as well as obstructive sleep apnea.
- -Some physicians think tonsillar hypertrophy may relate to desaturation of hemoglobin and increase the risk of sickling.
- -Tonsillectomy with adenoidectomy will improve the obstructive apnea for most patients.
Common Procedures for Young Individuals with SCD: CHOLECYSTECTOMY
Bilirubin gallstones occur frequently in all patients with hemolytic anemias—including sickle cell disease—the result of increased release of hemoglobin during breakdown of abnormal red blood cells.
Risk of Sepsis in Children with SCD
- -The decreased splenic function leads to decreased resistance to infection with encapsulated organisms (Streptococcus pneumoniae, Hib, Neisseria meningitidis).
- -When given to infants with sickling disorders, penicillin significantly decreases the risk of mortality from overwhelming sepsis.
- -Penicillin is usually continued until the child is 5 or 6 years of age; after this age there is little data to support its use except in patients who have had documented sepsis and bacteremia, or who have had their spleens removed.
Goals for the Comprehensive Visit for SCD
- How the family deals with the various complications that can occur.
- The frequency of painful or other vaso-occlusive problems.
- -This will give an indication of the need for other, more aggressive interventions such as the use of hydroxyurea. - How the family accesses health care.
- How the family is dealing with a chronic illness.
Expected Complications for Children with SCD
- jaundice
- anemia
- stroke
- respiratory problems
Immunization Recommendations for Children with SCD
The Haemophilus influenzae type b conjugate vaccine and 13-valent pneumococcal conjugate vaccine (Prevnar 13)-given at 2, 4 and 6 mo-have aided in protection against 2 bacteria that have been major leaders in M&M in children with SCD
Impairment of growth is common in children with sickle cell disease. This is probably multifactorial and may be due to any one or combination of the following:
Chronic anemia Poor nutrition Painful crises Endocrine dysfunction Poor pulmonary function
Important Signs in the Physical Exam in a Patient with SCD
- splenic enlargement
- sclera
- neurologic exam
Baseline Hemoglobin in SCD
between 6 and 9 g/dL (60-90 g/L). They accommodate to this level of hemoglobin very well, but the lower the baseline hemoglobin, the more difficult it is for the patient to withstand any acute change.
In a child with sickle cell disease, cough and breathing difficulty may indicate:
Acute chest syndrome:
- -Pneumonia
- -Intrapulmonary sickling
- -Pulmonary fat embolism
Acute chest syndrome (ACS)
Multilobar infiltrates (more commonly lower and middle lobes)
Effusions
Atelectasis
Pericarditis
can present with effusion and infiltrate on chest x-ray.
Congestive heart failure (CHF)
Lower lobe infiltrates and cardiomegaly are both consistent with a diagnosis of CHF.
Rib infarction
- -While there would not be pulmonary infiltrates, a pleural effusion might happen as a sequela of rib infarction.
- -Also, cardiomegaly and hypoxia would not usually be present (though patients with sickle cell disease may have baseline cardiomegaly).
Sepsis
- -Cardiomegaly would be present only if patient was in cardiogenic shock (although, as noted above, patients with sickle cell disease may have cardiomegaly at baseline).
- -New infiltrates would not be a usual finding unless the sepsis leads to acquired/adult respiratory distress syndrome (ARDS).
CBC Findings in Stress Response
Patients with sickle cell disease frequently demonstrate an exaggerated leukocytosis and thrombocytosis in response to stress.
Atelectasis
Definition:
A collapsed or airless segment of lung due to obstruction with distal collapse of the alveoli.
Risk:
Atelectasis is a serious risk in a child with chest pain. It can exacerbate acute chest syndrome, causing it even to become life-threatening.
Indications for RBC transfusion in ACS are not precise, but if a child experiences one of the following, a transfusion of packed red cells is recommended:
A fall in hemoglobin from baseline Increasing respiratory rate Worsening chest symptoms Declining O2 sats Progressive infiltrates on chest x-ray
When to Seek Emergency Care for a Patient with SCD
- fever
- splenic enlargement
- slurred speech
- chest pain
- rapid breathing
- INC pallor
- INC jaundice
- priapism
Various infectious agents have been reported in ACS including:
Viruses
Chlamydia
Mycoplasma
Bacteria
Differential Diagnosis of Fever, Respiratory Distress, and Chest Pain in Child with SCD
- ACS
- pericarditis
- CHF–Tachypnea is one of the most common signs of CHF in children.
- rib infarction
- sepsis
Parvovirus B19 causes aplastic anemia–SCD
especially in children with shortened RBC half-life. A mild anemia associated with parvovirus often goes unnoticed in healthy children. However, in patients with decreased RBC survival, such as sickle-cell patients, anemia can develop very rapidly and severely, along with decreases in the other cell lines (resulting in leukopenia and thrombocytopenia). In the above presentation, the presence of fever in a child with sickle cell disease should also raise concern for significant bacterial infection from encapsulated organisms like pneumococcus. This patient should have a blood culture and be started on empiric antimicrobial therapy pending screen labs and cultures
