Hidden Blood Loss and Its Possible Risk Factors in Full Endoscopic Lumbar Interbody Fusion

Background: Full endoscopic lumbar interbody fusion (Endo-LIF) is a representative recent emerging minimally invasive operation. The hidden blood loss (HBL) in an Endo-LIF procedure and its possible risk factors are still unclear. Methods: The blood loss (TBL) was calculated by Gross formula. Sex, age, BMI, hypertension, diabetes, ASA classification, fusion levels, surgical approach type, surgery time, preoperative RBC, HGB, Hct, PT, INR, APTT, Fg, postoperative mean arterial pressure, postoperative heart rate, Intraoperative blood loss (IBL), patient blood volume were included to investigate the possible risk factors by correlation analysis and multiple linear regression between variables and HBL. Results:Ninety-six patients (23 males, 73 females) who underwent Endo-LIF were retrospective analyzed in this study. The HBL was 240.11 (65.51, 460.31) mL (median [interquartile range]). Fusion levels (p = 0.002), age (p = 0.003), hypertension (p = 0.000), IBL (p = 0.012), PT (p = 0.016), preoperative HBG (p = 0.037) were the possible risk factors. Conclusion: Fusion levels, younger age, hypertension, prolonged PT, preoperative HBG are possible risk factors of HBL in an Endo-LIF procedure. More attention should be paid especially in multi-level minimally invasive surgery. The increase of fusion levels will lead to a considerable HBL.