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The Spine Blog

Friday, May 24, 2019

IV or PO TXA?

Tranexamic acid (TXA) is now widely accepted as an effective means to reduce blood loss during spinal deformity surgery, and it is now being adopted for any fusion surgery in which significant blood loss is anticipated. Most of the spine surgery literature has evaluated IV TXA, typically administered as an initial bolus followed by a continuous infusion for the remainder of the case. The total joints literature has demonstrated the efficacy of oral and topical TXA, though the spine literature has not evaluated the PO preparation. Advocates of PO TXA note the reduced cost and ease of administration. In order to compare IV and PO TXA in spinal fusion, Dr. Yu and colleagues from Detroit performed an RCT in which 83 patients undergoing lumbar or thoracolumbar fusion were randomized to receive IV or PO TXA. The IV medication was given as a 1 g bolus prior to incision followed by a second 1 g bolus prior to closure. The patients randomized to PO TXA received 1.95 g PO 2 hours prior to incision. The average fusion length was 3.8 levels, 15% underwent pedicle subtraction osteotomies, and 26% underwent interbody fusions. The two groups were very similar at baseline, though the IV group had a significantly lower BMI (28.5 vs. 32.1) and lower baseline platelet count (205 vs. 240). The IV group was also less likely to undergo an interbody fusion (16% vs. 38%). The primary outcome, drop in hemoglobin, was not significantly different between the two gropus (3.36 g/dL IV vs. 3.43 g/DL PO). The other outcome measures, including estimated blood loss, drain output, rate of post-operative transfusion, and rate of thromboembolic events, were not significantly different between the two groups. The authors concluded that PO TXA was equally as effective as IV TXA and recommended the use of PO TXA due to its lower cost ($14 vs. $53) and ease of administration.

The authors should be congratulated for successfully performing a Level 1 RCT addressing a clinically relevant question. The results strongly suggest that PO and IV TXA are equally as effective and have similarly safe side effect profiles. The authors do not comment on blinding, so one must assume the study was not blinded. It would have been relatively easy to blind the surgeons (and potentially the patients) to group assignment, though it is not clear that would have affected the results in a meaningful way. The main outcome measure, drop in hemoglobin, is not subjective and was unlikely subject to bias. The only other concern with the methodology is that the authors did not use a continuous IV infusion during surgery, and IV TXA given as a bolus is likely not circulating at a sufficient concentration to be effective in surgeries over four hours long (the average surgery was about 4 ½ hours). As such, the IV TXA patients undergoing longer surgeries may have had lower blood loss if a continuous infusion was performed for the duration of the case. While the conclusion that IV and PO TXA are equally effective is likely valid, it is unclear if PO TXA should be widely adopted. In the scope of a spinal fusion surgery that likely costs tens of thousands of dollars, a $40 savings is negligible. The authors do point out that changing to PO TXA could save the US healthcare system $20 million per year, though sadly that is a rounding error when it comes to national healthcare expenditures. The argument that administering PO TXA is easier than IV TXA is also questionable, as it requires that the medication is given 2 hours prior to incision. Some patients do not arrive until less than two hours before surgery, and it is easy to imagine that the dose is missed or delayed in the pre-operative holding area. At my institution, TXA is administered by anesthesia along with pre-operative antibiotics, and this is confirmed at the time out. In this model, if the TXA is overlooked, it is caught at the time out and administered prior to making the incision. This paper makes it clear that PO TXA is a reasonable option in systems that find using it advantageous. A more pressing question is defining the indications for TXA use. Given its good safety profile, it seems reasonable to consider using it in any lumbar or thoracolumbar fusion.

Please read Dr. Yu’s article on this topic in the June 1 issue. Would you consider using PO TXA at this point based on this article? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS
Associate Web Editor