Characteristics and results of platelet count decrease after lower extremity arthroplasty in patients receiving low-molecular-weight heparin

This study aims to evaluate changes in platelet count and causes of thrombocytopenia in the postoperative period in patients undergoing lower extremity arthroplasty; to determine the frequency of heparin-induced non-immune thrombocytopenia (HIT Type I) and immune thrombocytopenia (HIT Type II); and to contribute to postoperative hemogram monitoring. The study retrospectively examined a total of 120 patients who underwent lower extremity arthroplasty and received routine low molecular weight heparin (LMWH) prophylaxis between December 2011 and December 2015. Platelet and hemoglobin values were recorded in the preoperative period and at 8 hours postoperatively, as well as on days 1, 2, 3, 4, 5, and 10. A platelet count of <150×10⁹/L was considered thrombocytopenia. The likelihood of HIT Type II was assessed based on a preoperative value of ≥50% platelet decrease and using the 4T scoring system. A decrease in platelet count was observed in 98.3% of patients during the postoperative period. The median decrease ratio between the baseline value and the lowest platelet value was calculated as 15.16%. Thrombocytopenia was observed in 24 (20%) patients. Thrombocytopenia due to hemodilution or increased platelet consumption was detected in 12 (10%) of these patients, while HIT Type I was detected in 12 (10%) of them. No HIT Type II was observed in any patient. The most significant decrease in platelet count was observed within the first four days postoperatively, while values recovered from day 5 onwards and exceeded baseline levels. Changes in platelet count following lower extremity arthroplasty generally occur within the first four days after surgery and are mostly observed as postoperative hemodilutional thrombocytopenia and thrombocytopenia associated with accelerated platelet destruction related to fluid replacement and surgical hemostasis. HIT Type I occurs at a significant rate but does not cause clinical problems. In contrast, HIT Type II is a life-threatening condition, although it is extremely rare, and therefore, clinical awareness is of great importance.