Reduction in blood platelet size with increase in circulating numbers in the postoperative period and a comparison of the glass bead and rotating bulb methods for detecting changes in function.

The changes in blood platelet numbers, size, adhesiveness, and response to adenosine diphosphate have been followed for about a month after major operations performed on 19 patients. The well established increase in numbers was confirmed and reached a maximum of rather less than double the normal numbers in the third week. It was accompanied by a reduction of platelet size from 8.3mu(3) to 7.2mu(3), and by an increased responsiveness shown in all the tests employed. These abnormalities were preceded by an initial change in the reverse direction from that obtaining at the peak of the response. In this series the bead method proved superior, as a means of delineating the postoperative platelet response, to the rotating bulb method in tests of timing, proportional changes, and of discrimination.