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J Thorac Cardiovasc Surg 2003;125:739
© 2003 The American Association for Thoracic Surgery

Letters to the Editor

Preoperative platelet inhibition and bleeding after cardiopulmonary bypass

Department of Cardiac Surgery, Royal Sussex County Hospital, Brighton, United Kingdom^a
Department of Cardiac Surgery, University of Glasgow, Royal Infirmary, Glasgow, United Kingdom^b
Department of Medicine, Manchester Royal Infirmary, Manchester, United Kingdom^c

To the Editor:

Bizzari and associates ¹ studied clinical events and potential bleeding complications in a group of patients who had undergone emergency or urgent cardiac surgery after treatment with tirofiban hydrochloride. They observed that patients treated with tirobifan had a smaller decrease in platelet count during cardiopulmonary bypass; other platelet suppressants have similar effects. ^2,3 Preoperative platelet inhibition will reduce the platelet loss associated with cardiopulmonary bypass because a preferential loss of activated platelets is observed during the period of extracorporeal circulation. ^4,5 The hemostatic function of the preserved platelets would, however, be impaired by heparin-induced plasma changes. ⁶

The study was undertaken because of a concern that platelet inhibition may exacerbate bleeding after cardiopulmonary bypass. We among others have demonstrated that during cardiopulmonary bypass platelets lose the ability to form large stable aggregates (macroaggregates). ^6-9 This impairment persists for several hours postoperatively. ^7,8 Macroaggregation is important for platelet hemostatic function because it gives strength to a platelet plug and paves the way for clot retraction. As platelet macroaggregation is virtually abolished during cardiopulmonary bypass, ^6-9 we suggest that additional platelet suppression is unlikely further to impair hemostasis or increase bleeding during the immediate postoperative period. Furthermore, after cardiopulmonary bypass platelets appear resistant to aspirin, ¹⁰ an irreversible platelet inhibitor; it is therefore unlikely that even long-acting platelet suppressants that are administered preoperatively will significantly impair platelets late in the postoperative period. This would explain why patients who received platelet suppressants shortly before undergoing surgery using cardiopulmonary bypass did not appear to bleed excessively when compared with those who did not receive these drugs. ^1-3

References

1. Bizzarri F, Scolletta S, Tucci E, Lucidi M, Davoli G, Toscano T, et al. Perioperative use of tirofiban hydrochloride (Aggrastat) does not increase surgical bleeding after emergency or urgent coronary artery bypass grafting. J Thorac Cardiovasc Surg. 2001;122:1181-5.[Abstract/Free Full Text]
   
2. Faichney A, Davidson KG, Wheatley DJ, Davidson JF, Walker ID. Prostacyclin in cardiopulmonary bypass operations. J Thorac Cardiovasc Surg. 1982;8:601-8.
   
3. Dyke CM, Bhatia D, Lorenz TJ, Marso SP, Tardiff BE, Hogeboom C, et al. Immediate coronary artery bypass surgery after platelet inhibition with eptifibatide: results from PURSUIT. Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrelin Therapy. Ann Thorac Surg. 2000;70:866-71.[Abstract/Free Full Text]
   
4. Wahba A, Black G, Koksch M, Rothe G, Preuner J, Schmitz G, et al. Cardiopulmonary bypass leads to a preferential loss of activated platelets: a flow cytometric assay of platelet surface antigens. Eur J Cardiothorac Surg. 1996;10:768-73.[Abstract]
   
5. Muriithi EW, Belcher PR, Rao JN, Chaudhry MA, Nicol D, Wheatley DJ. The effects of heparin and extracorporeal circulation on platelet counts and platelet microaggregation during cardiopulmonary bypass. J Thorac Cardiovasc Surg. 2000:120;538-43.
   
6. Muriithi EW, Belcher PR, Day SP, Menys VC, Wheatley DJ. Heparin induced platelet dysfunction and cardiopulmonary bypass. Ann Thorac Surg. 2000;69:1827-32.[Abstract/Free Full Text]
   
7. Menys VC, Belcher PR, Noble MI, Evans RD, Drossos GE, Pillai R, et al. Macroaggregation of platelets in plasma, as distinct from microaggregation in whole blood (and plasma), as determined using optical aggregometry and platelet counting respectively, is specifically impaired following cardiopulmonary bypass in man. Thromb Haemost. 1994;72:511-8.[Medline]
   
8. Kawahito K, Kobayashi E, Iwasa H, Misawa Y, Fuse K. Platelet aggregation during cardiopulmonary bypass evaluated by a laser light-scattering method. Ann Thorac Surg. 1999;67:79-84.[Abstract/Free Full Text]
   
9. Belcher PR, Muriithi EW, Milne EM, Wanikiat P, Wheatley DJ, Armstrong RA. Heparin, platelet aggregation, neutrophils and cardiopulmonary bypass. Thromb Res. 2000;98:249-56.[Medline]
   
10. Zimmermann N, Kienzle P, Weber A-A, Winter J, Gams E, Schrör K, et al. Aspirin resistance after coronary artery bypass grafting. J Thorac Cardiovasc Surg. 2001:121:982-4.
    

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Muriithi, E. W. Articles by Menys, V. C. Search for Related Content PubMed PubMed Citation Articles by Muriithi, E. W. Articles by Menys, V. C.