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The Society of Thoracic Surgeons, Blood Conservation Guideline Task Force, Division of Cardiovascular & Thoracic Surgery, University of Kentucky Chandler Medical Center, CTW Building, Suite 320, 900 South Limestone, Lexington, KY 40536-0200
(Email: ferraris{at}uky.edu; ferraris{at}earthlink.net).
| Dr Ferraris discloses that he has financial relationships with AstraZeneca, Aventis, Bayer, Network for Advancement of Transfusion Alternatives (NATA), and The Medicines Company.
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Gourlay and colleagues [1] suggest that leukocyte depletion may be beneficial in limiting bleeding and blood transfusion after cardiac operations. Our review of the literature did not find evidence to confirm this speculation.
Several of the references cited by Gourlay and colleagues, and others identified by our guideline writers, compare the benefits of leukocyte depletion combined with other interventions including surface coating of the bypass circuit, aprotinin use, and other anti-inflammatory strategies. We do not believe that these references provide adequate evidence to support leukocyte depletion as a beneficial intervention for blood conservation, because the benefits may just as well have been caused by the other agents in the experimental designs. The best studies (ie, the highest levels of evidence) did not find any benefit of leukocyte depletion in limiting bleeding or blood transfusion [2, 3].
An important consideration in developing practice guidelines is to identify interventions that may be harmful. The potential for harm is the only thing that generates a class III recommendation for guideline purposes. There are at least two references identified by the guideline writers that suggest leukocyte depletion may cause harm [4, 5]. Because of the failure of leukocyte depletion in showing a benefit in limiting blood transfusion, and because of the potential harm, this intervention was given a class III recommendation. I should also point out that the overwhelming majority of the guideline writing and reviewing workforces agreed with this recommendation (see Appendix 2 of the Blood Conservation Guidelines) [6].
Gourlay and colleagues amplify an important feature of the practice guidelines. These guidelines are not laws, they are guidelines. Perhaps the most important part of the guideline document is the legal disclaimer that appears on the first page of the document. This disclaimer should be read by all surgeons who read the guideline document, and this disclaimer suggests that the ultimate judgment regarding the care of a particular patient must be made by the surgeon in light of the individual circumstances presented by the patient. If Gourlay and colleagues [1] find that leukocyte depletion limits bleeding and provides for better outcome in their patients at their institution, and if they can document these results, then there is nothing in the guidelines that prevents them from using this intervention, regardless of the class of recommendation.
There are two desirable outcomes from practice guideline development. First, implementation of practice guidelines limits wide variations in practice, and practice variation is undesirable. This may increase costs and cause worse outcomes. Adherence to practice guidelines improves patient outcomes. Another important result of the guideline development process is to identify deficits in the knowledge base. An example of a knowledge deficit identified by our guideline development is the management of clopidogrel in patients requiring coronary artery bypass grafting (CABG). Stopping clopidogrel in these patients risks acute thrombosis of drug-eluting stents, whereas continuation of clopidogrel risks excessive bleeding and possibly increased mortality during CABG. There is limited evidence available to provide a recommendation in this setting. An important side effect of the guideline development process is hypothesis generation and identification of future studies that need to be performed. It is possible that Gourlay and colleagues [1] are on the verge of finding something important by showing that leukocyte depletion may be a beneficial intervention. Future randomized trials may confirm this concept, but available evidence does not provide this yet.
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