139 Preservation and Clinical use of Platelets Flashcards

1
Q

Platelets circulate for a shorter time in thrombocytopenic patients ( ______ days) compared with normal subjects (8–10 days)

A

≤5 days

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2
Q

Daily requirement of platelets to maintain endothelial support

A

4.8 x 1010

Because one random donor platelet concentrate contains on average 8.3 × 1010 platelets, the daily requirement for endothelial support should be easily maintained with the transfusion of only one platelet concentrate per day.

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3
Q

The two mechanisms by which platelets are lost from circulation:

A

(1) senescence, whereby platelets are removed by the mononuclear phagocyte system;

(2) random, whereby platelets are consumed during hemostasis to provide endothelial support

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4
Q

Before the availability of platelets for transfusion, observational studies found the incidence of spontaneous bleeding increases at platelets counts of 100 × 109/L or less in children with acute leukemia, but minor and major bleeding began to increase (>1% chance of observable bleeding per patient-day) when the platelet count fell below ______ × 109/L.

A

Below 50 × 109/L

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5
Q

TRUE OR FALSE

More recent observations suggest that the amount of bleeding is not dependent on the platelet count as long as it is above 5 × 109/L.

A

TRUE

More recent observations suggest that the amount of bleeding is not dependent on the platelet count as long as it is above 5 × 109/L.

Life-threatening bleeding rarely occurs above platelet counts of 5 × 109/L to 10 × 109/L without disruption of the vessel wall.

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6
Q

Study that showed that bleeding occurred on 17% of the study days at platelet counts between 6 × 109/L and 85 × 109/L and increased to 25% when counts fell below 6 × 109/L

A

Platelet Dose (PLADO) study

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7
Q

WHO Bleeding Grade Categories

A

Grade 1: Minor bleeding

Grade 2: Bleeding requires intervention or
treatment, eg, nasal packing, bladder irrigation,
platelet transfusion or medications, to treat bleeding
Grade 2a: Grade 2 bleeding excluding skin manifestations

Grade 3: Bleeding requires red cell transfusion
related to treatment of bleeding or Significant intervention to treat bleeding, eg, endoscopy or surgery

Grade 4: Bleeding that is fatal or lifethreatening

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8
Q

TRUE OR FALSE

Several prospective randomized platelet transfusion trials have shown differences in spontaneous bleeding events when patients are transfused at platelet counts below 10 × 109/L versus 20 × 109/L

A

FALSE

Several prospective randomized platelet transfusion trials have shown no differences in spontaneous bleeding events when patients are transfused at platelet counts below 10 × 109/L versus 20 × 109/L or even versus 30 × 109/L, and a threshold for transfusion as low as 5 × 109/L may be safe.

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9
Q

Recommended cut-off for platelet transfusion by both the American Association of Blood Banks (AABB) in 2015 and Sanquin Blood Supply in 2011

A

Less than 10 × 109/L

Patients with active infection or fever, or those who are bleeding may require higher transfusion thresholds.

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10
Q

TRUE OR FALSE

At this time, TRAs cannot be routinely recommended as an adjunct to or replacement for platelet transfusions in patients with hypoproliferative thrombocytopenia

A

TRUE

At this time, TRAs cannot be routinely recommended as an adjunct to or replacement for platelet transfusions in patients with hypoproliferative thrombocytopenia

But clinical trials are ongoing

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11
Q

TRUE OR FALSE

Lumbar puncture (LP) can often be safely performed at platelet counts below 20 × 109/L.

A

TRUE

Lumbar puncture (LP) can often be safely performed at platelet counts below 20 × 109/L.

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12
Q

Platelet count generally accepted as appropriate for major neurosurgical procedures

A

100 × 109/L

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13
Q

Often considered to be a safe level of platelets for patients anticoagulated with warfarin or heparin therapy

A

40–50 × 109/L

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14
Q

Target platelet count in life-threatening bleeding, such as intracerebral bleeding or diffuse alveolar hemorrhage and diffuse microvascular bleeding

A

100 × 109/L

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15
Q

The incremental increase in platelet count after a platelet transfusion is dependent on:

A
  • Platelet dose (number)
  • Patient’s blood volume (which is, in turn, dependent on body size)
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16
Q

The corrected count increment (CCI), generally measured ______________________ after a platelet transfusion

A

30 minutes to 1 hour

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17
Q

Formula for corrected count increment (CCI)

A

(Posttransfusion Platelet Count- Pretransfusion Platelet Count) (Body Surface Area in Meters ) / Number of Platelets Transfused ( x10^11 )

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18
Q

Corrected count increment (CCI) considered “refractory” to platelet transfusions

A

CCI of less than 5 × 109/L on at least two consecutive occasions

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19
Q

Another indicator of platelet refractoriness

A

Two sequential one-hour platelet increments of 11 × 109/L or less

20
Q

Platelet refractoriness can be classified as:

A
  • Immune
  • Nonimmunologically mediated- most common
21
Q

The factors that most likely resulted in platelet refractoriness, in order of frequency:

A
  • (a) developing lymphocytotoxic antibodies
  • (b) being male, or female with two or more pregnancies
  • (c) heparin administration
  • (d) fever
  • (e) bleeding
  • (f) transfusion of γ-irradiated platelets
  • (g) receiving an increasing number of platelet transfusions

in order of frequency

22
Q

Patients with high anti-________ agglutinin titers may benefit from ABO-matched platelets.

A

anti-A agglutinin titers

23
Q

Patients who have been previously transfused or pregnant may fail to increase their platelet count after transfusion because of human leukocyte antigen (HLA) antibodies directed against the ________________ antigens.

A

Class I HLA antigens

24
Q

Reduce the rate of formation of HLA antibodies

A

Transfusion of leukocyte-reduced cellular blood components

25
Q

TRUE OR FALSE

Transfusion of platelets to patients with immune thrombocytopenia is appropriate only for life- or organ-threatening bleeding.

A

TRUE

Transfusion of platelets to patients with immune thrombocytopenia is appropriate only for life- or organ-threatening bleeding.

26
Q

TRUE OR FALSE

Platelet transfusion was associated with an increased risk of arterial thrombosis in patients with thrombotic thrombocytopenic purpura and heparin-induced thrombocytopenia, but not in patients with immune thrombocytopenia.

A

TRUE

Platelet transfusion was associated with an increased risk of arterial thrombosis in patients with thrombotic thrombocytopenic purpura and heparin-induced thrombocytopenia, but not in patients with immune thrombocytopenia.

27
Q

Platelets are obtained by two different methods:

A
  • Platelet concentrates from whole blood
  • Apheresed Platelets
28
Q

The FDA requires at least:
* ____ × 1010 platelets/ concentrate
* ____ × 1011 platelets/apheresis collection

A
  • 5.5 × 1010 platelets/ concentrate
  • 3.0 × 1011 platelets/apheresis collection
29
Q

Two methods used to prepare platelets

A
  • Platelet-rich plasma (PRP) method
  • Buffy-coat (BC) method
30
Q

Advantage of Apheresed Platelets

A
  • Reducing transfusion-transmitted infections
  • Reducing the incidence of platelet alloimmunization
31
Q

TRUE OR FALSE

The bacterial risk associated with plasma transfusions is high because they are stored at 12 °C.

A

FALSE

The bacterial risk associated with platelet transfusions is high because platelets are stored at 22 °C.

32
Q

TRUE OR FALSE

Differences in platelet product, ABO matching, or storage duration did not affect time to bleeding

A

TRUE

Differences in platelet product, ABO matching, or storage duration did not affect time to bleeding

33
Q

Adverse event that occurred more frequently with platelets (421.7/100,000) compared with other blood components in the U.S. between 2010 and 2012 (the most recent hemovigilance report at the time of this publication).

A

Transfusion Reactions

34
Q

The majority of transfusion reactions were:

A
  • Allergic (46.8%)
  • Febrile nonhemolytic transfusion reactions (36.1%)
35
Q

TRUE OR FALSE

Premedication does not alter the rate of allergic transfusion reactions

A

TRUE

Premedication does not alter the rate of allergic transfusion reactions

36
Q

Indications for providing leukoreduced platelet products:

A
  • (a) reduction of platelet alloimmunization
  • (b) prevention of cytomegalovirus transmission by transfusion
  • (c) reduction in febrile transfusion reactions
37
Q

Indicated to prevent transfusion-related GVHD

A

γ-Irradiation

38
Q

γ-Irradiation with the usual dose of

A

25 Gy

39
Q

Indications for γ-Irradiated platelets:

A
  • (a) patients receiving stem cell transplantation and/or fludarabine chemotherapy
  • (b) intrauterine transfusions
  • (c) granulocyte transfusions
  • d) crossmatched, HLA-matched, or directed donation blood products
  • (e) patients who are severely immunocompromised, usually because of their disease or its treatment (including newborns that are premature, low birth weight, or have erythroblastosis fetalis; patients with congenital immunodeficiencies; and patients with hematologic malignancies, as well as some solid tumor malignancies such as neuroblastoma, sarcoma, and Hodgkin disease)
40
Q

Volume reduction is also used for patients with:

A
  • Recurrent allergic reactions
  • Febrile nonhemolytic transfusion reactions that are not mitigated by premedication
  • When the recipient and donor have an ABO incompatibility
41
Q

Effective for patients with severe allergic reactions, as well as critical for patients with IgA deficiency to prevent anaphylactic transfusion reactions.

A

Platelet washing

42
Q

Systems used in pathogen reduction

A
  • Amotosalen (Intercept system)
  • Riboflavin (Mirasol system)
43
Q

The major risk of platelet storage at 22 °C is

A

Bacterial overgrowth

Usually because of inadequate sterilization of the venipuncture site

44
Q

The FDA has approved platelet storage up to ___ days

A

7 days

Most bacteria have been demonstrated to grow to confluence by 3 to 5 days.

Therefore, once platelets have been stored beyond 5 days, there is little increased risk from bacterial overgrowth.

45
Q

When platelets were collected by a Haemonetics apheresis machine, they could be stored for

A

13 days

46
Q

Half-life of Aspirin

A

2-3 hours