RESUMO
BACKGROUND:Hidden blood loss, after total knee arthroplasty, attracts surgeons’ attention. There are various hypotheses about etiopathogenisis of hidden blood loss, but no one can reasonably explain its mechanism. OBJECTIVE:To research the correlation of free fatty acids and hidden blood loss after total knee arthroplasty, and explore the etiology and mechanism of hidden blood loss after total knee arthroplasty. METHODS:Clinical data of 42 osteoarthritis patients who underwent primary unilateral total knee arthroplasty were colected in this study. Intraoperativeand postoperative dominant blood loss was recorded. Blood samples were colected preoperatively and 24, 48, 72, and 96 hours postoperatively. Changes in hemoglobin, erythrocyte count, hematocrit and free fatty acids were detected in blood. Hidden blood loss was obtained by Gross equation. Simultaneously, stains were added to the blood smear. Changes of cels morphology were observed under a microscope. RESULTS AND CONCLUSION:(1) Hemoglobin and erythrocyte count decreased significantly at 24 and 48 hourspostoperatively, and significant differences were determined as compared with that preoperatively (P< 0.01). (2) Free fatty acids levels increased significantly within 24 hours after surgery, and decreased to preoperative levels at 72 and 96 hours later.Hidden blood loss was also significant at 24 and 48 hours after surgery, which showed positive correlation with free fatty acids content. (3) A plenty of abnormal erythrocytes were observed under the microscope. At 24 and 48 hours postoperatively, erythrocyte shrinkage and damage were mainly presented. At 96 hours, no significant abnormality was found. (4) These results indicated that free fatty acids were strongly associated with postoperative hidden blood loss. Surgeon should pay attention to the fatty droplets which may enter into the circulation in the process of reaming the femoral canal so as to reduce intraoperative total blood loss.