In thrombocytopenia bleeding may occur related to the deficiency in platelets. Administration of platelet products can supply sufficient platelets to restore hemostasis.


Basic Equation Approach


ideal number of platelet units to give =

= ((increment wanted) * (blood volume) / (number of platelets per unit))


actual number of platelet units to give =

= ((ideal number) / (fractional yield you "expect"))


For further description of this method, see Maximal Platelet Count Increment (MPI), below.


Heuristic Approach


Rule of Thumb : Ideally, a 70 kg person with 1.8 sq meter BSA should see a 5,000-10,000/µL increase in platelet count for each unit of platelets given. This assumes that the minimum number of platelets per unit is (5.5 * 10^10).


As the blood volume increases or decreases much from the "average", the less predictable this heuristic will work.


Based on the heuristic approach:

Step 1: Decide the increment you want

Step 2: Guess how you expect the patient to respond (whoa!) to a single unit (where along the spectrum of 5,000 - 10,000 platelets/µL per unit) = "guess at increment per unit"

Step 3: [(increment wanted) / (guess at increment per unit)] = number of units to give


Annotation to heuristic:

(1) A BSA of 1.8 square meters works out to a blood volume of 4.71 liters (4.71 * 10^6 µL).

(2) If the minimum number of platelets was present in a single unit, then the increment for 1 unit of platelets should be ((5.5 * 10^10) / (4.71 * 10^6)) approximates 10,000.

(3) Since you can expect that more platelets are given than the minimum, the heuristic assumes less than ideal (ranges down to 50%) recovery.

(4) One unit of platelet concentrate usually increases the platelet count of an adult with a blood volume of 5,000 mL by about 5,000/µL (Jacobs 1994).


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