Blood Product Usage Case Studies


CASE 4


Clinical History:

The parents of a 4 year-old boy bring him to the pediatrician to ask about the child's new propensity to form large bruises for no obvious reason, and the onset of fevers. A complete blood count and peripheral smear are obtained. These reveal the following:

  • White blood cell count = 90 X 109/L (normal = 5.3-11.5 X 109/L)

  • Hemoglobin = 8.3 g/dL (normal = 10.5-12.7 g/dL)

  • Hematocrit = 25% (normal = 31.7-37.7%)

  • Platelet count = 20,000 / mm3 (normal = 204-405 X 109/L)

  • PT = 10 seconds (normal = 10.7-15 seconds)

  • PTT = 26 seconds (normal = 25-40 seconds)

The peripheral smear reveals a predominant population of large white blood cells with a high nuclear-to-cytoplasmic ratio, and fine chromatin, suspicious for blasts.

The pediatrician explains to the parents that the most likely diagnosis is acute lymphoblastic leukemia (ALL). He explains the need for their consent to draw more blood to send for flow cytometry, get a bone marrow biopsy, and to perform a lumbar puncture as part of the staging process. He also asks their consent to give blood products.

Questions:

  1. If you were the pediatrician, which product would be your first priority? Why?

    2. Platelets. The count is too low to perform an invasive procedure such as a bone marrow biopsy or a lumbar puncture; the patient may bleed excessively and compromise the spinal cord.

    A consensus-development conference held in 1986 determined the following regarding platelet counts:

    • A patient is unlikely to bleed if platelets are greater than 50,000/microliter (assuming the platelets have normal function).

    • A patient is likely to have spontaneous hemorrhage if the platelet count is less than 5,000/microliter.

    • Between 5,000 and 10,000/microliter, there is an increased risk of spontaneous hemorrhage.

    • Between 10,000 and 50,000/microliter, there is an increased risk of hemorrhage during a hemostatic challenge such as surgery or trauma.

    • A platelet count of 20,000/microliter might be fine if the physician was not going to perform any invasive procedures. But for a lumbar puncture, platelets are indicated.

  2. For an invasive procedure, above what value do you want to help assure that a patient will not bleed?

    3. You will find that this number is somewhat subjective and depends on the clinician. Based on the above data, one needs a platelet count greater than 50,000/microliter, and many people aim for a count of 100,000/microliter or higher.

  3. What other blood products is this child likely to need during the course of his therapy?

    4. Because chemotherapy will affect all cell lines, he is likely to need packed red cells as well as platelets after chemotherapy. White cell production may be stimulated with administration of granulocyte colony-stimulating factor (G-CSF). One would not expect his coagulation parameters to change, so he should not need FFP.

  4. The physician evaluates the child's fever and finds evidence on physical examination and chest radiograph for a pneumonia in one lung. Antibiotics are administered and acetaminophen is given for the fever. Do fevers and drugs impact how well a person will respond to a unit of platelets?

    5. Yes. Fevers and drugs (especially antifungal agents) will lead to increased platelet destruction and a patient will not get as much of an increase from a unit of platelets as a patient without fevers,etc.

  5. What is the difference between a platelet pool and an apheresis unit of platelets?

    6. Platelet pool:

    + + + + +

    Made from 4 - 8 units of platelets separated from donated whole blood, so there are 4 - 8 "donor exposures" as far as viral transmission risks. Generally a pooled unit will not have as many platelets as an apheresis unit, so the rise in the patient's count will not be as high. A platelet pool is less expensive than an apheresis unit.

    Apheresis unit:

    =

    An apheresis unit is taken from only one donor, who has platelets removed by apheresis techniques during a donation. There is thus only one donor exposure per unit. The platelet count also is usually higher than in a pooled unit. The main disadvantage is that the unit is more expensive to make than a pooled unit.