139 Preservation and Clinical use of Platelets Flashcards
Platelets circulate for a shorter time in thrombocytopenic patients ( ______ days) compared with normal subjects (8–10 days)
≤5 days
Daily requirement of platelets to maintain endothelial support
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.
The two mechanisms by which platelets are lost from circulation:
(1) senescence, whereby platelets are removed by the mononuclear phagocyte system;
(2) random, whereby platelets are consumed during hemostasis to provide endothelial support
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.
Below 50 × 109/L
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.
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.
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
Platelet Dose (PLADO) study
WHO Bleeding Grade Categories
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
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
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.
Recommended cut-off for platelet transfusion by both the American Association of Blood Banks (AABB) in 2015 and Sanquin Blood Supply in 2011
Less than 10 × 109/L
Patients with active infection or fever, or those who are bleeding may require higher transfusion thresholds.
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
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
TRUE OR FALSE
Lumbar puncture (LP) can often be safely performed at platelet counts below 20 × 109/L.
TRUE
Lumbar puncture (LP) can often be safely performed at platelet counts below 20 × 109/L.
Platelet count generally accepted as appropriate for major neurosurgical procedures
100 × 109/L
Often considered to be a safe level of platelets for patients anticoagulated with warfarin or heparin therapy
40–50 × 109/L
Target platelet count in life-threatening bleeding, such as intracerebral bleeding or diffuse alveolar hemorrhage and diffuse microvascular bleeding
100 × 109/L
The incremental increase in platelet count after a platelet transfusion is dependent on:
- Platelet dose (number)
- Patient’s blood volume (which is, in turn, dependent on body size)
The corrected count increment (CCI), generally measured ______________________ after a platelet transfusion
30 minutes to 1 hour
Formula for corrected count increment (CCI)
(Posttransfusion Platelet Count- Pretransfusion Platelet Count) (Body Surface Area in Meters ) / Number of Platelets Transfused ( x10^11 )
Corrected count increment (CCI) considered “refractory” to platelet transfusions
CCI of less than 5 × 109/L on at least two consecutive occasions
Another indicator of platelet refractoriness
Two sequential one-hour platelet increments of 11 × 109/L or less
Platelet refractoriness can be classified as:
- Immune
- Nonimmunologically mediated- most common
The factors that most likely resulted in platelet refractoriness, in order of frequency:
- (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
Patients with high anti-________ agglutinin titers may benefit from ABO-matched platelets.
anti-A agglutinin titers
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.
Class I HLA antigens
Reduce the rate of formation of HLA antibodies
Transfusion of leukocyte-reduced cellular blood components
TRUE OR FALSE
Transfusion of platelets to patients with immune thrombocytopenia is appropriate only for life- or organ-threatening bleeding.
TRUE
Transfusion of platelets to patients with immune thrombocytopenia is appropriate only for life- or organ-threatening bleeding.
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.
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.
Platelets are obtained by two different methods:
- Platelet concentrates from whole blood
- Apheresed Platelets
The FDA requires at least:
* ____ × 1010 platelets/ concentrate
* ____ × 1011 platelets/apheresis collection
- 5.5 × 1010 platelets/ concentrate
- 3.0 × 1011 platelets/apheresis collection
Two methods used to prepare platelets
- Platelet-rich plasma (PRP) method
- Buffy-coat (BC) method
Advantage of Apheresed Platelets
- Reducing transfusion-transmitted infections
- Reducing the incidence of platelet alloimmunization
TRUE OR FALSE
The bacterial risk associated with plasma transfusions is high because they are stored at 12 °C.
FALSE
The bacterial risk associated with platelet transfusions is high because platelets are stored at 22 °C.
TRUE OR FALSE
Differences in platelet product, ABO matching, or storage duration did not affect time to bleeding
TRUE
Differences in platelet product, ABO matching, or storage duration did not affect time to bleeding
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).
Transfusion Reactions
The majority of transfusion reactions were:
- Allergic (46.8%)
- Febrile nonhemolytic transfusion reactions (36.1%)
TRUE OR FALSE
Premedication does not alter the rate of allergic transfusion reactions
TRUE
Premedication does not alter the rate of allergic transfusion reactions
Indications for providing leukoreduced platelet products:
- (a) reduction of platelet alloimmunization
- (b) prevention of cytomegalovirus transmission by transfusion
- (c) reduction in febrile transfusion reactions
Indicated to prevent transfusion-related GVHD
γ-Irradiation
γ-Irradiation with the usual dose of
25 Gy
Indications for γ-Irradiated platelets:
- (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)
Volume reduction is also used for patients with:
- Recurrent allergic reactions
- Febrile nonhemolytic transfusion reactions that are not mitigated by premedication
- When the recipient and donor have an ABO incompatibility
Effective for patients with severe allergic reactions, as well as critical for patients with IgA deficiency to prevent anaphylactic transfusion reactions.
Platelet washing
Systems used in pathogen reduction
- Amotosalen (Intercept system)
- Riboflavin (Mirasol system)
The major risk of platelet storage at 22 °C is
Bacterial overgrowth
Usually because of inadequate sterilization of the venipuncture site
The FDA has approved platelet storage up to ___ days
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.
When platelets were collected by a Haemonetics apheresis machine, they could be stored for
13 days
Half-life of Aspirin
2-3 hours
