139 Preservation and Clinical use of Platelets

Question 1

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

Answer 1

≤5 days

Question 2

Daily requirement of platelets to maintain endothelial support

Answer 2

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.

Question 3

The two mechanisms by which platelets are lost from circulation:

Answer 3

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

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

Question 4

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.

Answer 4

Below 50 × 109/L

Question 5

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.

Answer 5

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.

Question 6

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

Answer 6

Platelet Dose (PLADO) study

Question 7

WHO Bleeding Grade Categories

Answer 7

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

Question 8

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

Answer 8

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.

Question 9

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

Answer 9

Less than 10 × 109/L

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

Question 10

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

Answer 10

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

Question 11

TRUE OR FALSE

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

Answer 11

TRUE

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

Question 12

Platelet count generally accepted as appropriate for major neurosurgical procedures

Answer 12

100 × 109/L

Question 13

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

Answer 13

40–50 × 109/L

Question 14

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

Answer 14

100 × 109/L

Question 15

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

Answer 15

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

Question 16

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

Answer 16

30 minutes to 1 hour

Question 17

Formula for corrected count increment (CCI)

Answer 17

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

Question 18

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

Answer 18

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

Question 19

Another indicator of platelet refractoriness

Answer 19

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

Question 20

Platelet refractoriness can be classified as:

Answer 20

• Immune
• Nonimmunologically mediated- most common

Question 21

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

Answer 21

• (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

Question 22

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

Answer 22

anti-A agglutinin titers

Question 23

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.

Answer 23

Class I HLA antigens

Question 24

Reduce the rate of formation of HLA antibodies

Answer 24

Transfusion of leukocyte-reduced cellular blood components

Question 25

TRUE OR FALSE

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

Answer 25

TRUE

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

Question 26

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.

Answer 26

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.

Question 27

Platelets are obtained by two different methods:

Answer 27

• Platelet concentrates from whole blood
• Apheresed Platelets

Question 28

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

Answer 28

• 5.5 × 1010 platelets/ concentrate
• 3.0 × 1011 platelets/apheresis collection

Question 29

Two methods used to prepare platelets

Answer 29

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

Question 30

Advantage of Apheresed Platelets

Answer 30

• Reducing transfusion-transmitted infections
• Reducing the incidence of platelet alloimmunization

Question 31

TRUE OR FALSE

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

Answer 31

FALSE

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

Question 32

TRUE OR FALSE

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

Answer 32

TRUE

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

Question 33

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).

Answer 33

Transfusion Reactions

Question 34

The majority of transfusion reactions were:

Answer 34

• Allergic (46.8%)
• Febrile nonhemolytic transfusion reactions (36.1%)

Question 35

TRUE OR FALSE

Premedication does not alter the rate of allergic transfusion reactions

Answer 35

TRUE

Premedication does not alter the rate of allergic transfusion reactions

Question 36

Indications for providing leukoreduced platelet products:

Answer 36

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

Question 37

Indicated to prevent transfusion-related GVHD

Answer 37

γ-Irradiation

Question 38

γ-Irradiation with the usual dose of

Answer 38

25 Gy

Question 39

Indications for γ-Irradiated platelets:

Answer 39

• (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)

Question 40

Volume reduction is also used for patients with:

Answer 40

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

Question 41

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

Answer 41

Platelet washing

Question 42

Systems used in pathogen reduction

Answer 42

• Amotosalen (Intercept system)
• Riboflavin (Mirasol system)

Question 43

The major risk of platelet storage at 22 °C is

Answer 43

Bacterial overgrowth

Usually because of inadequate sterilization of the venipuncture site

Question 44

The FDA has approved platelet storage up to ___ days

Answer 44

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.

Question 45

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

Answer 45

13 days

Question 46

Half-life of Aspirin

Answer 46

2-3 hours