| JOURNAL HOME | CME HOME | THIS MONTH | PAST ISSUES | ETOC | COLLECTIONS |
| AUTHORS | REVIEWERS | EDITORIAL BOARD | FEEDBACK | RSS | HELP |
| ||||||||||||||
| ||||||||||||||
|
|
|
|
||||||||||||
|
||||||||||||||
Division of Cardiovascular Anesthesia and Intensive Care, Policlinico di Monza, Monza, Italy
To the Editor:
Pleym et al. (1) evaluated the effects of administering tranexamic acid (TA) as a single bolus dose in patients treated with aspirin until the day before coronary surgery. Even if they demonstrated that TA reduced postoperative bleeding significantly, they concluded affirming that TA cannot be recommended for all patients, because this drug might theoretically induce thrombotic complications. They come to this conclusion due to the lack of differences in terms of allogeneic transfusion in their patients treated or not treated with TA.
My first consideration is that the authors based the sample size calculation for their study on postoperative bleeding, and not on perioperative transfusions. The authors report 20% of patients transfused in the placebo group, versus 17.5% in the TA group, which signifies a difference of about 10% between the two groups. To show statistically significant difference with these numbers, the authors should have enrolled about 3000 patients per group.
A second consideration is that one would consider as clinically significant the reduction, in the TA group, of more then 40% in terms of amount of packed red cells transfused (13 units in 7 patients, that is 1.86 units per patient transfused in the TA patients, versus 22 units in 8 patients, corresponding to 2.75 units per patient transfused in the placebo group). I think the significance would have had a greater result greater considering also the blood lost and reinfused postoperatively; probably without this blood-sparing technique, which is not routinely used in all cardiosurgical centers, the patients of the placebo group would have required further units of packed red cells, amplifying the differences among the groups.
A last consideration regards the modality of the administration of TA. The efficacy of the protocol of the authors is not surprising for the simple reason that the surgical times reported by the authors are so brief that the single bolus dose used guarantees adequate concentrations of the drug for the entire period of surgery (2). There are concerns regarding the efficacy of this protocol in case of prolonged times required by more complex surgery.
In conclusion, I think it is arguable to advise against the treatment with TA on the basis of theoretical and undemonstrated increased risk of thrombotic complications, whereas the efficacy of TA in reducing bleeding and allogeneic transfusion has been evidenced by previous published studies as well as also by Pleym et al. (3–4).
References
St. Elisabeth Department of Cardiothoracic Surgery, Trondheim, Norway
In Response:
We thank Dr. Casati for his comments on our article (1). The aim of our study was to investigate the effect of a single dose of tranexamic acid on postoperative bleeding and transfusion requirements in patients scheduled for primary coronary artery bypass grafting (CABG) who were treated with aspirin until the day before surgery. The aim was not to investigate tranexamic acid administration in more complex cardiac surgical procedures. Obviously, further studies must be done to determine whether the mode of administration of tranexamic acid used in this study is also effective in reducing postoperative bleeding in more complicated procedures with prolonged surgical and cardiopulmonary bypass times. We would, however, like to point out that our drug administration procedure is simple and safe, and that the duration of action of this regimen is unknown, as no hard clinical data on minimum effective serum concentrations exists.
The patients in the tranexamic acid group had a numerically smaller number of packed red cells transfused compared with the placebo group (13 units in 7 patients versus 22 units in 8 patients), and Dr. Casati considers this difference to be clinically significant. The difference was, however, not statistically significant. As pointed out by Dr. Casati, our sample size calculation was based on differences in postoperative bleeding and not on differences in transfusion requirements. We therefore agree that a small but clinically significant difference in transfusion requirements may be present without being detected by this study due to lack of power, which we also briefly discussed in our article. In addition, we discussed other factors that may have influenced the negative results on transfusion requirements, and the retransfusion of mediastinal shed blood to all patients is one of these factors. However, since the difference in transfusion requirements was not statistically significant, one must also consider the possibility that the numerically smaller number of packed red cells transfused to the tranexamic acid group compared with the placebo group was caused by chance alone.
Most studies on the effect of tranexamic acid in cardiac surgery have been prospective, randomized, and placebo controlled. This study design is not suitable to demonstrate rare but potentially serious adverse effects caused by drug treatment (2). Tranexamic acid has been associated with arterial and venous thrombosis in case reports (3,4). The possibility that tranexamic acid can cause potentially harmful side effects also in cardiac surgery has been raised by several previous authors and is a concern among many clinicians. In the final part of our article we state that our study does not preclude the possibility that certain groups of patients undergoing various cardiac procedures may benefit from treatment. However, because we were unable to demonstrate a reduction in transfusion requirements in the tranexamic acid group, and because there are some concerns about the safety of the drug, it is still our opinion that routine prophylactic treatment with tranexamic acid in primary CABG cannot be recommended.
References
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
