1.Pooled, random donor platelet concentrates. Each individual unit has about 50 ml of fresh plasma. A standard pool size for an adult is currently 6 units. Therefore, the volume of one pool is approximately 300 ml. Shelf life of original unit = 5 days. After pooling, the platelet infusion must start within 4 hours.
Dosage: rule of thumb is 1 unit per 10 kg of body weight. If clinicians ask for pool bigger than 6 units because they have an extra-large adult, that is acceptable (certainly up to 10 or 12 platelets). An average adult should have an adequate dose with 6 units. Beware of requests for pools larger than 10 units. More is not necessarily better! If an adequate response does not occur with the standard size dose, then something is going on in the patient. Giving a hundred units of platelets may not make the platelet count go up in such a patient. First question to ask is: did the patient stop bleeding even if the platelet count did not go up as expected? If so, no more platelets may be necessary. If surgery is pending and the bleeding is projected at that time, suggest that a pool of 6 or 8 units be given immediately prior to surgery and then we will send a second pool as needed. Do not send more than one pool to the patient at a time unless circumstances are very unusual indeed!
2.Apheresis platelets (single donor platelets). Each unit contains the equivalent of 6 to 8 units of pooled platelets and approximately 250 ml of fresh plasma. If you have a choice between single donor platelets and a pool of platelets, if all other variables are equal, use the apheresis platelets first because they have a lower risk of transmitting infectious disease.
Dosage: 1 apheresis collection = 1 dose for an adult or large child. For smaller patients, one apheresis unit can be split into two doses and issued at separate times. When single donor platelets are being issued to an adult or older pediatric patient the two bags are combined into one. Shelf life of the unit becomes 24 hours at that time (because of decreased surface area for respiration).
ABO group of platelets. Platelets should be ABO compatible whenever possible. See Compatible Blood Groups For Transfusion. The plasma in the platelets should be compatible with the RBCs of the recipient. If no ABO compatible platelets are available, you have the following choices:
There is no definitive right or wrong choice. Pick whichever serves the needs of the individual patient in question best.
Rh group of platelets. Platelets do not express Rh antigens, but the RBCs that contaminate a unit of platelets do. Platelet concentrates should be Rh compatible with the recipient whenever possible. However, platelets from Rh negative donors are frequently in short supply. If no Rh negative platelets are available for an Rh negative recipient, you may:
Indications. See also appendix 1 in paper supplement. Thrombocytopenia: patients at bed rest, with no procedure planned and platelet count >20,000/µl do not generally need transfusion with platelets. Exception: if they are demonstrating "platelet-type" bleeding (e.g. mucosal bleeding, petechiae, oozing from veni-puncture sites), I wouldn't object to trying a platelet transfusion. If the count is below 20,000/µl, platelet transfusion can be given if requested, bleeding or not. Prior to surgery, platelets can be administered if the platelet count is <100,000. For a minor procedure (e.g. line placement) it may be appropriate to get by with a count >50,000 but < 100,000.
Cardiopulmonary bypass surgery: Do not place a lot of emphasis on the platelet count. Circulating platelets may be poorly functional because of damage from the pump. You may authorize platelet transfusion to cardiac patients even if the count is >100,000 if the patient is showing evidence of platelet-type bleeding. Encourage transfusion of platelets in such patients to occur after the patient comes off the bypass circuit whenever possible. A bleeding time determination is not required.
Platelet dysfunction: A patient with a history of known platelet dysfunction, or a patient with recent use of anti-platelet drugs (e.g. aspirin, persantine) may require platelet transfusion despite a normal platelet count. Ideally, a bleeding time would already be available to demonstrate the dysfunction. However, on nights and weekends, you do not need to require a bleeding time be done to prove the dysfunction, because it may delay treatment and cause unnecessary work by the hematology lab personnel. I would recommend trying one dose of platelets. If that doesn't stop the bleeding, then further work-up is encouraged (e.g. maybe a heme/onc consult is in order).
Contraindications. Unless life-threatening hemorrhage is occurring, platelet transfusion is generally not indicated for: ITP, TTP, post-transfusion purpura, uremia.
Evaluation of efficacy. Please encourage a post-transfusion platelet count. Generally this is sampled one hour after transfusion, but sampling as early as fifteen minutes is useful. The expected increment for an average size adult is a rise in the count of 5,000 to 10,000 per each unit in the pool transfused. Note: a lack of expected rise does not mean the transfusion was totally ineffective. The most helpful indicator is whether the patient quit bleeding.
Platelet count prior to issue of platelets. It is encouraged that a platelet count be available for review prior to release of platelet concentrates. However, this is not an absolute requirement. If a situation exists where the platelets are perceived to be needed STAT and a count has not been done, yet the need for platelets makes sense (e.g. massive bleeding or leukemia patient), then go ahead and release one pool, but ask that a purple top (EDTA) tube be sent concurrently for platelet count. In these cases we want ongoing monitoring of efficacy of therapy, but we won't delay treatment to get it before the transfusion is issued. The platelet counts are done by hematology and the clinicians should send the sample directly there as a STAT "walk-in". Their runner then needs to wait for the results.
Use of apheresis platelets prior to completing testing. Occasionally you will get a request to issue an apheresis platelet unit from a relative or friend to a patient prior to all infectious disease testing being completed. DO NOT OKAY THIS WITHOUT CHECKING WITH BLOOD BANK FACULTY FIRST!! There are very few situations where this would be appropriate, and the clinicians often don't understand our regulations in this matter, so they will put pressure on you to give in. It must be documented to be a life-threatening emergency that can only be treated with those particular platelets. In reality, most requests for this early release involve frantic parents or spouses that fear the general blood supply. The FDA will not allow early release for this reason.
Use of apheresis platelets for patients other than the intended recipient. If an apheresis platelet unit will expire soon, the blood bank may contact you to see if the patient for whom it was collected indeed is going to use it soon. If that patient does not need the unit in the near future, see if the physician will OK us using it for another patient. They are usually willing to do this, especially if they know their patient has yet another unit on the shelf, so you might check with the lab about other platelets available for that patient. The platelet supply is always limited and we cannot afford to waste platelets.
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