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This Article Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Bradley O. Hofer Edward D. Verrier Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Hofer, B. O. Articles by Vocelka, C. Search for Related Content PubMed Articles by Hofer, B. O. Articles by Vocelka, C.

J Thorac Cardiovasc Surg 1994;108:1148-1149
© 1994 Mosby, Inc.

LETTERS TO THE EDITOR

Platelet-rich plasmapheresis in cardiac surgery: Efficacy may yet be demonstrated

Division of Cardiothoracic Surgery
University of Washington
Seattle, WA 98195

Reply to the Editor:

Drs. Stover and Siegel have suggested that two recent studies, including ours, failed to show efficacy of platelet-rich plasma harvest and reinfusion in either valve or coronary surgery because of "inadequate methods."

We agree that the technique of platelet-rich plasma collection may have an effect. In our previous discussion we specifically mentioned the probable improved efficacy of large platelets that are located near the red cell mass during centrifugation. Techniques that maximize this harvest may well show additional benefits. Simple harvesting of autologous whole blood before cardiopulmonary bypass is a much simpler approach, but not always appropriate. Additional platelet numbers may also add to efficacy, as theorized by Drs. Stover and Siegel, but increasing the duration of plasmapheresis to a period that is sometimes longer than the cardiopulmonary bypass run itself seems excessive without documented significant effects on coagulation. Additionally, the difference between 2.5 x 10⁹ platelets (collected in 57 minutes per Stover and Siegel) and 1.72 to 2.15 x 10⁹ platelets (collected in 15 minutes by us) does not seem adequate to justify 42 minutes of pheresis. Controlled trials like ours, establishing efficacy of these techniques, similar to those that have documented the efficacy of aprotinin, are eagerly awaited.

Truly proving statistically and scientifically that an intervention does not work is a difficult task. Our "negative study" did not eliminate the possibility that the treatment has a measurable, but small, effect beyond the power of the study. Unfortunately, the two studies sited by Drs. Stover and Siegel as "proving" efficacy are either nonrandomized or nonblinded or both. To compare our results with these studies, we included a figure in the article comparing the 95% confidence intervals in our study with those in four other studies, including the two mentioned by the Drs. Stover and Siegel. Even if the effects of larger platelets in greater numbers are accepted without rigorous documentation, then it remains of concern that in the four studies cited in Fig. 2 of our article the difference in chest drainage was at most minor: the treatment groups had approximately 100 to 350 ml less chest tube drainage over 24 hours, frequently with a low hematocrit value. This may be significant in a statistical sense in the context of unblinded and nonrandomized studies, but it may not be significant clinically. If the technique was proved efficacious, even to limited extent, and was made inexpensive, simple, and reproducible, these mild effects would be adequate to promote widespread adoption of the technique.

Drs. Stover and Siegel do not address two important issues. First, there is a wide individual variation in the degree of coagulopathy after cardiopulmonary bypass. The effects of large numbers of reinfused platelets and associated factors in such coagulopathic patients might be dramatic. One of the continuing shortcomings of plasmapheresis of platelet-rich plasma, by any method, is the inability to target these coagulopathic patients and spare the others an added expense and procedure. The second is that there may be other ameliorative effects of plasmapheresis on the complications of cardiopulmonary bypass, as suggested by Davies and associates. Well-controlled studies documenting these effects should be pursued.

This Article Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Bradley O. Hofer Edward D. Verrier Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Hofer, B. O. Articles by Vocelka, C. Search for Related Content PubMed Articles by Hofer, B. O. Articles by Vocelka, C.