ABSTRACT
Thrombocytosis [platelet counts >400 ' 103/mm3] following coronary artery bypass grafting has been described to occur frequently [20-30%] and to be associated with thrombotic complications postoperatively. The purpose of the present study is to establish when the peak value of platelet count occurs, and how high it is, as well as to determine the duration of thrombocytosis. Thirty consecutive patients undergoing elective coronary artery bypass grafting, who subsequently developed postoperative thrombocytosis [group 1] were considered for the study. Another 30 patients with platelet counts within normal limits postoperatively served as controls [group 2]. Platelet count was monitored on a weekly basis during 5 weeks postoperatively. Patient characteristics, operation data and cardiopulmonary bypass data in group 1 did not differ from group 2 patients, except for a higher incidence of hyperlipidemia, i.e., 97% [29/30 patients] in group 1 compared to 40% [12/30] in group 2 [p < 0.001]. Neither deaths nor nonfatal myocardial infarctions occurred during the study period. Postoperative thrombocytosis was diagnosed on 6.1 +/- 1.5 days postoperatively, and peak platelet count reached 14 +/- 4.0 days postoperatively [6-21 days]. The highest platelet count observed was 905,000/mm3. Platelet counts returned to normal values within 5 weeks. Three late vein graft occlusions occurred in all groups, and thus coinciding with the maximum platelet count observed. Conclusions: Postoperative thrombocytosis is a potentially dangerous complication, with an increased risk for vein graft occlusion. Postoperative thrombocytosis, when it occurs, is diagnosed around the 6th postoperative day, reaches its peak 2 weeks postoperatively and may last as long as 5 weeks. Close surveillance of patients with postoperative thrombocytosis is emphasized