Comparison of the Total and Hidden Blood Loss in Patients Undergoing Open and Minimally Invasive Transforaminal Lumbar Interbody Fusion.

PURPOSE: This study examined the volume of hidden blood loss (HBL) and compared perioperative blood loss between minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) and open transforaminal lumbar interbody fusion (O-TLIF).

METHODS: Forty-eight patients who were treated with MI-TLIF and 59 patients treated with O-TLIF were enrolled in this study. Patients' height, weight, and preoperative and postoperative hematocrit (Hct) were recorded and used to calculate total blood loss (TBL) according to the Gross formula. Each patient's HBL was calculated. The data were further analyzed by the Student t test and the χ2 test.

RESULTS: The visible blood loss (VBL) was 186 ± 95 mL in the MI-TLIF; however, the HBL (423 ± 233 mL; 66.5 ± 16.1% of TBL) was twice the VBL. The VBL in the O-TLIF group was 471 ± 147 mL, and the HBL was 271 ± 223 mL (31.3 ± 23.9% of TBL). Although TBL in MI-TLIF (602 ± 251 mL) was less than in O-TLIF (742 ± 275 mL), the HBL was significantly higher (P < 0.01). No difference in postoperative blood loss was observed between the 2 groups. Seven and 10 patients had preoperative anemia in the MI-TLIF group and the O-TLIF group, respectively, and 32 and 45 postoperatively.

CONCLUSION: HBL is seriously underestimated and accounts for a large percentage of TBL in both MI-TLIF and O-TLIF. A correct understanding of HBL can ensure patient safety and improve postoperative rehabilitation.