Comparison of  Total and Hidden Blood Loss in Patients Undergoing Single-Level Open and Unilateral Biportal Endoscopic Transforaminal Lumbar Interbody Fusion

Abstract urpose: This study aimed to compare total blood loss (TBL) and hidden blood loss (HBL) in patients undergoing single-level open transforaminal lumbar interbody fusion (O-TLIF) and unilateral biportal endoscopic transforaminal lumbar interbody fusion (ULIF).Methods: A total of 28 patients who underwent ULIF and 30 patients who underwent O-TLIF from March 2020 to October 2021 were retrospectively reviewed. The Nadler’s formula was employed to estimate the patient’s blood volume (PBV), Gross’s formula to estimate TBL, and Sehat’s formula to estimate HBL. The obtained data were then analyzed with independent t test、chi-squared test, and analysis of covariance.Results: TBL and measured blood loss (MBL) in ULIF group (360.00±245.74 ml, 117.43±83.09 ml) was significantly lower than O-TLIF group (542.29±233.25ml, 306.30±108.98ml). Nevertheless, the HBL in ULIF group was higher than that in O-TLIF group (242.57±242.49 ml vs 235.99±236.53 ml), however this was not statistically significant. (P=0.917). The HBL was 67.38± 25.63% of TBL in ULIF group and 43.52±17.39% of TBL in O-TLIF group. Patients in ULIF group had lower TBL and MBL, shorter duration of drainage, lower postoperative anemia, and shorter postoperative hospital stay compared to those in O-TLIF group.Conclusions: Perioperative HBL should not be neglected in patients undergoing ULIF or O-TILF, as it accounts for a large percentage of TBL in both groups. ULIF is associated with lower TBL and MBL, postoperative anemia, shorter postoperative hospital stays compared with O-TLIF.