Pediatric Examination and Board Review (157 page)

BOOK: Pediatric Examination and Board Review

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Platelet transfusions are most useful in states of platelet hypoproduction, such as for patients receiving chemotherapy, in conditions of bone marrow hypoplasia such as Fanconi anemia, aplastic anemia, and in conditions with intrinsic platelet dysfunction, such as Wiskott-Aldrich syndrome, Bernard-Soulier syndrome, or Glanzmann thrombasthenia. Platelet transfusions are less likely to increase platelet counts in cases of increased platelet consumption, such as ITP, disseminated intravascular coagulation (DIC), Kasabach-Merritt syndrome, or in cases of platelet sequestration from hypersplenism. The transfused platelets in cases of increased consumption or sequestration will be rapidly consumed or sequestered. Correction of thrombocytopenia in these cases requires treatment for the underlying condition rather than platelet transfusions.

12.
(A)
FFP is a plasma product isolated from whole blood by centrifugation. Rapid freezing is used to preserve the plasma proteins, which include clotting factors II, V, VII, VIII, IX, X, XI, XII, and other proteins such as protein C, protein S, antithrombin III, complement factors, and immunoglobulins. FFP contains small amounts of fibrinogen, factor XIII, and von Willebrand factor, but these factors can be found in higher concentrations in cryoprecipitate, generated from rapid thawing of FFP.

Clotting factors are predominantly synthesized in the liver, and so hepatic insufficiency is associated with clotting factor deficiencies that result in prolongation of the PT and PTT. Replacement of these factors with FFP is frequently necessary to control bleeding. Because FFP is a poor source of fibrinogen, it should not be used as a source of fibrinogen replacement for a patient with hypofibrinogenemia; instead, cryoprecipitate should be used as needed. For patients with single factor deficiencies, such as in patients with hemophilia, replacement of factor with FFP would require large volumes and exposures to large numbers of donors, each with added risk of transfusion-related infections. Therefore, factor replacement with purified or recombinant products, which have lower risks of transmission of viral infections because of postsynthetic processing, is preferred for treatment of any bleeding episodes in these patients.

In patients receiving anticoagulant therapy, reversal of the anticoagulant action is frequently required, either to control excessive bleeding or before surgical procedures. Heparin functions as an anticoagulant by inhibiting serine proteases in the coagulation cascade, including thrombin-mediated generation of fibrin. The effects of heparin can be reversed rapidly by administration of protamine, a mixture of polypeptides that binds to heparin and neutralizes its inhibitory effect on the coagulation proteases. FFP is less effective in reversing the effects of heparin because the excess heparin will inhibit FFP-derived factors as well. In patients being treated with warfarin sodium, the vitamin K– dependent clotting factors (factors II, VII, IX, and X) are depleted and can be replaced on an emergent basis for severe bleeding with FFP. However, for control of nonemergent bleeding or to reverse the effects of warfarin sodium, vitamin K replacement is the preferred method of treatment, with rapid synthesis of the factors by the liver occurring in the presence of vitamin K to correct the deficiency.

13.
(C)
Blood transfusions are associated with a small risk of viral transmission and infection, with potential blood-borne pathogens including human immunodeficiency virus (HIV), hepatitis B and C viruses, cytomegalovirus (CMV), and EBV. Other viruses that are primarily spread via respiratory droplets, such as influenza, respiratory syncytial virus, and varicella zoster, are not spread by blood transfusions. Blood products are aggressively screened, both by donor history and serologic testing, to decrease the chances of a transfusion-related infection. Non-blood cell containing blood products are treated further to decrease the transmission rate of viruses. The current risks of viral transmission (per units of blood transfused) are approximately 1 in 2 million units for HIV and 1 in 500,000 units for hepatitis C. Approximately a third of packed red blood cell units are CMV-positive and can cause CMV infection in recipients who are CMV-negative. The viral transmission rates for products such as FFP and cryoprecipitate are much lower because of the extra treatment, but they are still not completely risk free.

14.
(B)
Reactions to blood product transfusions occur in 1-10% of transfusions and can range from mild fever and chills to anaphylaxis and shock. Reactions occur more commonly in patients who have received prior transfusions. Acute reactions occur within 24 hours of the transfusion and can have a variety of presentations. Acute hemolytic transfusion reactions because of ABO blood type mismatch are generally the most severe, with clinical features that include fevers, chills, anxiety, nausea, vomiting, shortness of breath, hypotension, hemoglobinemia, hemoglobinuria, renal failure, and DIC. Simple febrile reactions to the presence of donor cytokines can also be associated with fevers, chills, nausea, vomiting, and headaches but are not associated with hemoglobinemia or hemoglobinuria. Allergic reactions because of host antibodies to donor plasma proteins can also occur, and can range from minor urticaria to anaphylaxis. Chronic transfusion reactions can also occur from 4 days to several weeks posttransfusion. Delayed hemolytic reactions are usually a result of alloimmunization to minor blood group antigens from prior blood transfusions, and they are usually less severe than acute reactions. Delayed transfusion reactions are usually associated with mild fevers, fatigue, and weakness and laboratory features of hemolysis such as increased reticulocytes, increased indirect bilirubin, decreased haptoglobin, and peripheral spherocytosis. Hemoglobinuria is rare in delayed transfusion reactions. Myoglobinuria is not a feature of either acute or chronic transfusion reactions.

15.
(A)
Radiation therapy is associated with a wide range of complications, which vary depending on the radiation site and dose. Central nervous system radiation is associated with cognitive delays, hormonal abnormalities (such as growth hormone deficiency and thyroid dysfunction), and increased risk of cerebrovascular disease. Thoracic radiation is associated with cardiac damage (ranging from cardiomyopathy to restrictive pericarditis to myocardial infarction from increased atherosclerosis) and with lung damage (fibrosis or restrictive lung disease). Abdominal irradiation is associated with injury to abdominal organs, primarily gonadal failure and infertility. Furthermore, radiation therapy is associated with an increased risk of secondary malignancies at the sites of radiation. Diabetes mellitus is not a common complication of radiation therapy.

16.
(A)
Anthracyclines such as doxorubicin are associated with cardiac toxicity and can cause both acute and delayed cardiomyopathy with congestive heart failure. Anthracyclines are not associated with any pulmonary complications. Platinum compounds such as cisplatin are associated with renal toxicity and ototoxicity with high-frequency hearing loss. Cyclophosphamide, a commonly used alkylating agent, is also associated with renal toxicity, and its metabolites can irritate the bladder wall, resulting in hemorrhagic cystitis. High-dose steroid therapy has a long list of side effects and complications, including hypertension, hyperglycemia, behavioral changes, and growth delay but can also cause avascular necrosis, particularly of the femoral head. Adverse reactions to vincristine include neuritic pain, constipation, hair loss, sensory loss, paresthesia, difficulty in walking, slapping gait, loss of deep-tendon reflexes, and muscle wasting. Generalized sensorimotor dysfunction may become progressively more severe with continued treatment.

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CASE 91: A 6-YEAR-OLD WITH FEVERS, FATIGUE, AND BRUISING

A 6-year-old child is brought to your clinic by her parents for recurrent fevers, extreme fatigue, and bruising on her legs. She was a previously well child with no past medical history but was noted by her parents to be “very tired” starting about 1 week ago. Her activity level dropped significantly and she seemed to be “sleeping all the time,” according to her mother. She also began having daily fevers 3 days ago, and yesterday was noted to have large bruises on her legs bilaterally, despite no history of trauma. Her parents deny any medication use or any ingestions. The family history is negative for any significant medical problems. Before the past week she had been going to school and doing well.

On physical examination, the child is pale and tiredappearing. Her temperature is 102°F (38.9°C) orally. She has a few petechiae in her oropharynx and diffuse cervical lymphadenopathy. She has a 2/6 systolic ejection murmur. Her liver and spleen are both palpable 1 cm below the costal margin. Her legs have multiple large ecchymoses.

Her complete blood count revealed a white blood cell count of 65,000/μL, a hemoglobin of 6.4 g/dL, and a platelet count of 18,000/μL. The differential has 84% large white blood cells with minimal agranular pale blue cytoplasm and large nuclei with very fine chromatin and large nucleoli.

SELECT THE ONE BEST ANSWER

1.
The patient’s most likely diagnosis is which of the following?