Patient Encounter 2

LK is a 15-year-old female with a history of sickle cell disease (HbS).

PMH: Cholecystectomy at age 11 years; admitted for vasoocclusive crises five times over the past year; acute chest syndrome at age 13 and 14; immunizations up-to-date; multiple blood transfusions

FH: Father with SC trait; mother with SCD

SH: Student in the 9th grade; denies alcohol or drug use; is sexually active

Meds: Lortab 7.5 mg tablets orally every 4 to 6 hours as needed for pain; ibuprofen 600 mg orally three times a day as needed for pain; Folic acid 1 mg orally daily

The medical team wants to start LK on hydroxyurea.

Is she a candidate for hydroxyurea? Why or why not?

What initial laboratory work is required before initiating hydroxyurea?

Identify treatment goals for hydroxyurea in LK.

What is the initial dose and how will you monitor for efficacy?

What patient counseling is needed?

How will you monitor for toxicity?

Several methods of transfusion may be used, including simple transfusion, exchange transfusion, or erythrocytapher-esis. The goal of chronic transfusion therapy is to maintain the HbS level at less than 30% (0.30) of total hemoglobin concentration. Transfusions are usually administered every 3 to 4 weeks depending on the HbS concentration. For secondary stroke prevention, current studies have indicated that lifelong transfusion may be required, with increased incidence of recurrence once transfusions are stopped.5

The benefits of transfusion should be weighed with the risks. Risks associated with transfusions include allo-immunization (sensitization to the blood received), hyper-viscosity, viral transmission, volume overload, iron overload, and transfusion reactions. Approximately 18% to 30% of SCD patients who receive transfusions will experience alloimmunization, which can be minimized by the use of leukocyte-reduced RBCs or HLA-matched units. Viral transmission is still a concern, despite increased screening of blood donors and units. While the risk of contraction of AIDS has decreased dramatically, hepatitis C remains a concern. All SCD patients should be vaccinated for hepatitis A and B, and should be serially monitored for hepatitis C and other infections. Parvovirus occurs in 1 of every 40,000 units of RBCs and can be associated with acute anemia and multiple sickle cell complications.5 Iron overload remains a concern among those patients maintained on chronic transfusions for greater than 1 year. Counsel patients to avoid excessive dietary iron and monitor serum ferritin regularly. Chelation therapy with deferoxamine or deferasirox should be considered when the serum ferritin level is greater than 1,500 to 2,000 ng/mL (1,500-2,000 mcg/ L). Deferoxamine should be initiated at 20 to 40 mg/kg daily (to a maximum of 1-2 g/dav) over 8 to 12 hours subcutaneously, and has been associated with growth failure. Monitor children receiving deferoxamine for adequate growth and development on a regular basis. Deferasirox should be initiated at 20 mg/kg daily, and is available in a tablet that should be dispersed in water, orange juice, or apple juice and taken or-

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ally 30 minutes before food. ' Monitor all chelation patients for auditory and ocular changes on a yearly basis. Exchange transfusions may also be helpful in cases of iron overload.

Sickle cell hemolytic transfusion reaction syndrome is a unique problem in SCD patients. Due to alloimmunization, an acute or delayed transfusion reaction may occur. Delayed reactions typically occur 5 to 20 days post-transfusion. Alloantibodies and autoantibodies resulting from previous transfusions can trigger the reaction, in which patients develop symptoms suggestive of a pain crisis or worsening symptoms if they are already in crisis. A severe anemia after transfusion also may occur due to a rapid decrease in hemoglobin and hematocrit, along with a suppression of eryth-ropoiesis. Further transfusions may worsen the clinical picture due to autoimmune antibodies. Recovery may occur only after ceasing all transfusions, and is evidenced by a gradual increase in hemoglobin with reticulocytosis5,9

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