Since its introduction in 2000, several studies have reported HBL in various types of orthopedic surgeries. Sehat et al. (11) found that mean HBL was 735 mL, accounting for 50% of TBL during total knee arthroplasty. Yoji Ogura et al. (19) showed that during 2- to 3-level posterior lumbar fusion, HBL varies from 678-1,267mL. Importantly, Foss and Kehlet et al. (20) reported that HBL was consistently associated with in-hospital complications and extended length of hospital stay. But as for now, no studies have reported HBL in ULIF. Here, we performed a retrospective analysis of HBL and TBL during ULIF and O-TLIF.
Michael et al.(21) reported that the IBL of ULIF was 65±38mL. However, ULIF’s IBL was minimal and difficult to calculate because of the volume of saline solution used for irrigation. Thus, in this study, the IBL of ULIF was neglected and incorporated into the calculations of HBL. HBL may result from blood hemolysis (22, 23), extravasation of blood into tissue compartments (24), and free fatty acids mediated oxidative damage of RBCs and Hb (25).
Previous studies (26–29) indicate that gender, multilevel, operative time, fibrinogen level, ASA classification, autologous and allogeneic transfusion, BMI, and surgical method were independent risk factors for HBL in posterior lumbar interbody fusion. Here, to investigate the effect of surgical method on HBL, we used other variables as control variables. Our data show that mean HBL was 242.57±242.49 mL in ULIF (constituting up to 67.38% of TBL) and 235.99±236.53ml in O-TLIF (constituting up to 43.52% of TBL). Surprisingly, mean HBL did not differ significantly between the two groups. However, the proportion of HBL in the two groups was significantly different. Our data indicate that HBL level was considerable and that it was the most important contributor to TBL in both ULIF and TLIF, which is consistent with past findings(12, 30). The difference in HBL composition between the groups may be explained by the following. 1) One non-negligible reason is that IBL in ULIF was neglected and factored into the HBL calculation. 2) The higher radiofrequency used in ULIF may have generated more oxidizing species that damaged RBCs and Hb. 3) HBL might be affected by the “learning curve” that accompanies the introduction of any new surgical method, resulting in higher HBL being observed during ULIF in the initial cases.
In our study, the MBL in O-TLIF (306.30±108.98mL) was significantly higher than in ULIF (117.43±83.09mL). ULIF involved two minimally invasive incisions; one for endoscopic viewing and the other for the insertion and manipulation of surgical tools. The advantages of ULIF include being minimally invasive, involving less muscular dissection, better surgical view, and more precise operation. These factors may explain the lower TBL in the ULIF group. Moreover, considering that ULIF was wholly performed in aqueous media, we pulled with all strength to hemostasis because even minor bleeding can obstruct the surgeon field of vision. Moreover, Xu et al. (31) pointed out that the components of drainage changed radically with time. Thus, rather than the drainage volume, the true blood component of the drainage should be taken into account. In contrast with O-TLIF, ULIF leaves a high volume of water in the muscle and spinal space following saline irrigation. From this, it is expected that there was more water in ULIF drainage. Thus, the true blood volume was less than the drainage volume we described and the true difference between the two groups may be larger.
Perioperative anemia is significantly associated with complications and length of hospital stay (32, 33). TBL only accounted for 8.73±6.35% of PBV in ULIF, which was markedly lower than in the O-TLIF group. As shown on Figure 3, lower TBL reduced the incidence of postoperative anemia in the ULIF group. As expected, relative to O-TLIF, ULIF was associated with significantly shorter postoperative hospital stay. HBL is the leading cause of perioperative anemia and hidden blood loss and perioperative anemia may be minimized by various interventions. A recent study (34) found that tranexamic acid reduces HBL during posterior lumbar interbody fusion surgery. Hong Qian et al(35) found out that antioxidants attenuate oxidative stress-induced HBL in rats. However, more research is needed to identify new strategies for reducing HBL.
This study has some limitations. First, being retrospective, this study is inevitably susceptible to bias. Secondly, the study’s sample size was relatively small. Thirdly, disregarding ULIF’s IBL may have influenced our findings. Finally, studies (36, 37) show that fluid shifts may not be completed in all patients in 2 or 3 days after the operation. Thus, the HctPost we used to calculate TBL may not precise.