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

LETTERS TO THE EDITOR

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

Department of Anesthesia
Stanford University School of Medicine
Stanford, CA 94305

To the Editor:

In a recent article, Tobe and associates ¹ reported no significant effect of platelet-rich plasmapheresis on blood loss or on homologous blood product transfusion in a group of patients undergoing primary coronary artery bypass grafting In subsequent discussion, Dr. Wernly concluded that "PRP [platelet-rich plasma] offers minimal, if any, beneficial effect" and that the "authors' study has helped significantly to define the role of PRP [platelet-rich plasma] in cardiac surgery." In related anesthesia literature, Ereth and associates ² recently reported thatautologous "platelet-rich plasma did not reduce perioperative bleeding or transfusion requirements in repeat valvular surgery." We believe these negative results may reflect inadequate methods rather than a true lack of efficacy of platelet-rich plasmapheresis; we are thus concerned that a potentially valuable technique for reducing blood loss and transfusion requirements in cardiac surgery may be prematurely dismissed on the basis of these current reports.

Tobe and associates harvested "platelet-rich plasma" using the Haemonetics Plasma Saver (Braintree, Mass.). Specifically, they collected 8 to 10 ml/kg of "platelet-rich plasma" with mean platelet counts of 200,000 and 215,000/µl in the control and treatment groups, respectively. Not only does this quantity of platelets represent an average yield of fewer than three units of platelets for an 80 kg patient, but it is also striking that the mean platelet concentration in the "platelet-rich plasma" is less than the mean platelet concentration in the study patients' whole blood. One must question any anticipated therapeutic value from this low platelet number, even when attempting to account for the "freshness" of these platelets versus blood-bank products. ³ The authors believe that their negative results regarding the efficacy of platelet-rich plasmapheresis, when compared with previous studies claiming beneficial effects of the technique, are likely the result of their blinded study design. However, Jones and colleagues, ⁴ also using a Haemonetics plasma separator system but with a longer pheresis time (57 minutes versus 15 minutes), reported favorable results after obtaining platelet-rich plasma with mean total platelet counts of 2.5 x 10¹¹. These platelet yields, representing more than four units of platelets, are considerably higher than the yields obtained by Tobe and associates. Moreover, Davies and coworkers ⁵ also reported beneficial effects of platelet-rich plasmapheresis by using Electomedics (Englewood Colo.) technology with mean yields of more than six units of platelets per patient before cardiopulmonary bypass. Given the high platelet yields, this latter technique possibly harvested a significant number of the large and potent platelets that are left behind in the packed erythrocyte layer during plasmapheresis with the Haemonetics Plasma Saver. ² The negative results of Tobe's group may thus be a consequence of blinding or a result of the low platelet dose.

Before invoking study design as the explanation for different outcomes, one must be careful to critically evaluate the methods used by various investigators. It is possible that a technique for platelet-rich plasmapheresis with a significantly greater yield of platelets might simply be more efficacious than the technique as performed by Tobe and coworkers. Although the recent report by Ereth's group also casts doubt on the efficacy of methods that yield fewer than three units of platelets, the mean yield of more than six units of platelets obtained by Davies and coworkers lends credibility to the concept that a therapeutic quantity of autologous platelets may be obtained before cardiopulmonary bypass.

Tobe and coworkers have demonstrated that the removal and postbypass reinfusion of autologous platelets, with an average yield of fewer than three units, has little or no significant therapeutic benefit in patients undergoing primary coronary bypass. We still believe that an alternative technique that consistently yields a therapeutic quantity of platelets might significantly affect the transfusion of platelets and other homologous blood products associated with cardiac surgery and cardiopulmonary bypass.

References

1. Tobe CE, Vocelka C, Sepulvada R, et al. Infusion of autologous platelet rich plasma does not reduce blood loss and product use after coronary artery bypass. J THORAC CARDIOVASC SURG 1993;105:1007-14.[Abstract]
   
2. Ereth MH, Oliver WC, Beynen FMK, et al. Autologous platelet-rich plasma does not reduce transfusion of homologous blood products in patients undergoing repeat valvular surgery. Anesthesiology 1993;79:540-7.[Medline]
   
3. Owens M, Holme S, Heaton A, Sawyer S, Cardinali S. Post-transfusion recovery of function of 5-day stored platelet concentrates. Br J Haematol 1992;80:539-44.[Medline]
   
4. Jones JW, McCoy TA, Rawitscher RE, Lindsley DA. Effects of intraoperative plasmapheresis on blood loss in cardiac surgery. Ann Thorac Surg 1990;49:585-90.[Abstract]
   
5. Davies GG, Wells DG, Mabee TM, Sadler R, Melling NJ. Platelet-leukocyte plasmapheresis attenuates the deleterious effects of cardiopulmonary bypass. Ann Thorac Surg 1992;53:274-7.[Abstract]
   

This article has been cited by other articles:

				J. T. Christenson, J. Reuse, P. Badel, F. Simonet, and M. Schmuziger Plateletpheresis Before Redo CABG Diminishes Excessive Blood Transfusion Ann. Thorac. Surg., November 1, 1996; 62(5): 1373 - 1378. [Abstract] [Full Text]

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