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TO THE EDITOR: We read with great interest the recent article by Kushioka et al.1 (Kushioka J, Yamashita T, Okuda S, et al: High-dose tranexamic acid reduces intraoperative and postoperative blood loss in posterior lumbar interbody fusion. J Neurosurg Spine 26:363–367, March 2017) regarding the use of intravenous tranexamic acid (TXA) for single-level posterior lumbar interbody fusions (PLIFs). The authors conducted a nonrandomized, retrospective, comparative cohort study with 30 patients in each group and found that patients who received intravenous TXA had lower intraoperative and postoperative blood loss without any reported complications. We commend the authors on their effort to investigate the effectiveness and safety of intravenous TXA. There are, however, several issues regarding the methodology and the implications of this article that we wish to discuss. First, the authors refer to the TXA protocol in this study as “high dose.” Although there is currently no universally accepted definition, in the adult spinal deformity literature a “high-dose” TXA protocol typically implies a loading dose ranging from 50 to 100 mg/kg, followed by a 10–20 mg/kg/hr infusion.2,4 In this study, 2 separate doses of 2000 mg of TXA were given 15 minutes prior to the incision and again 16 hours postoperatively. This dosing protocol resulted in patients with higher body mass getting a much lower effective dose of TXA than patients with lower body mass. For example, a patient that weighed 100 kg would be getting a 20 mg/kg dose, whereas a patient weighing 50 kg would be getting 40 mg/kg with the single 2000 mg loading dose. It would have been helpful if the authors included the weight range for the patients in the study to give the readers an idea of the effective dose of TXA patients actually received in the study. Second, the size and design of the study make it likely that the results overestimate the effect of TXA in this patient population. Estimating intraoperative blood loss is typically an inaccurate process and, in the absence of a description of the specific methods used in this study, one has to assume that precise methods such as weighing sponges and carefully measuring volumes were not employed. In addition, although the authors state that “the drain was routinely removed 40 hours after the operation,” no data are provided to show that all drains were removed after the same amount of time. A systematic variation in duration of drainage could introduce significant bias to the results. Furthermore, 5 different surgeons performed the procedures in the study. Surgeon-related factors and variation in surgical technique can also influence estimated blood loss (EBL). Finally, the unblended design of the study introduces the potential for unintentional bias favoring the experimental treatment. A randomized controlled trial conducted by Wang et al.3 in 2013 did not find statistically significant differences in EBL for single-level PLIFs. In our clinical experience, TXA is an effective agent in reducing blood loss in major spinal surgery such as in deformity correction involving long-segment fusions, osteotomies, or vertebral column resections. Its use in routine single-level degenerative cases, however, must be weighed against the risk of rare complications unlikely to be captured in a small study such as this. The readers should carefully consider the results of this and other studies on TXA before adopting it for routine degenerative cases.

Letter to the Editor. Utility of intravenous tranexamic acid in single-level posterior lumbar interbody fusions