Background: Hidden blood loss (HBL) often occurs after joint replacement; however, the mechanism of HBL is not clear. We conducted a prospective study to analyze the correlation between high-level free fatty acids (FFA) and erythrocyte injury, and explore the pathologic mechanism of hidden blood loss (HBL) after total knee arthroplasty (TKA).
Methods: Perioperative blood indexes were tested in 120 patients who underwent unilateral total knee replacement for end-stage knee osteoarthritis. The changes in FFA, reactive oxygen species (ROS), hemoglobin (Hb), and red blood cells (RBC) in the blood samples were detected. The activity of glutathione peroxidase (GSH-Px), total superoxide dismutase (T-SOD) and hydrogen peroxide (H2O2) levels were measured. Morphologic changes of blood cells were analyzed under a microscope.
Results: HBL occurred in all patients after TKA. The Hb and RBC decreased significantly 24 h after surgery (P <0.05), while FFA and ROS concentration were substantially elevated, and heteromorphic red blood cells appeared under the microscope. The hemoglobin content decreased to its lowest level at 48 h after the operation (P<0.01). With the increase of FFA and ROS levels, HBL appeared more obvious (P<0.01). GSH-PX activity, T-SOD activity, and H2O2 levels significantly decreased compared to preoperative tested samples (P<0.01). Microscopically, atypical erythrocytes increased significantly with cellular rupture and lysis identified.
Conclusions: High levels of FFA in blood can induce oxidative stress and damage red blood cells, leading to the occurrence of HBL after surgery.
Trial registration: Chinese Clinical Trials Registry (the trial number: ChiCTR17010681, URL: http://www.chictr.org.cn).
Keywords: Hidden blood loss; free fatty acids; reactive oxygen species; total knee arthroplasty.
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