Exposure to ultrasound decreases the recalcification time of platelet rich plasma.

-Human blood was withdrawn, anticoagulated with citrate, and centrifuged, yielding platelet rich plasma (PRP). Recalcification times (i.e. the time taken to form a clot following the addition of sufficient calcium ions) were measured with a semiautomatic device. There were no changes in the recalcification time of PRP sample immediately following exposure to continuous wave 1 MHz ultrasound at intensities in the range 0.065--2 W/era -'. However. subsequent measurements showed an irreversible time dependent decrease of the recalcification time of an asymptotic value which was invariably less than that of the controls. This behavior can be interpreted as a time dependent alteration to the platelet population.