New Blood Conservation Guidelines on Antiplatelet Therapy
Reed Miller
March 16, 2011 (Chicago, Illinois)
— The new guidelines on blood conservation in surgery incorporate
recent evidence on antiplatelet therapy while continuing to emphasize
the importance of preoperative risk assessment [1].
The 2011 update to the Society of Thoracic Surgeons (STS) and the
Society of Cardiovascular Anesthesiologists (SCA) blood conservation
clinical practice guidelines, published in the March 2011 issue of the Annals of Thoracic Surgery, include significant changes to the societies' first set of blood conservation recommendations in 2007.
"Not all patients undergoing cardiac procedures have equal risk of
bleeding or blood transfusion. An important part of blood resource
management is recognition of patients' risk of bleeding and subsequent
blood transfusion," the writing committee, led by Dr Victor Ferraris (University of Kentucky, Lexington), explains in the document.
"There is almost no evidence in the literature to stratify blood
conservation interventions by patient risk category. Nonetheless, logic
suggests that patients at highest risk for bleeding are most likely to
benefit from the most aggressive blood management practices."
"A small fraction of the patients account for most of the blood
transfusion, so there's unquestionably a high-risk group," and the
guidelines are primarily aimed at managing that group, Ferraris told
heartwire.
An important component of preoperative risk assessment identified in
the new guidelines but not addressed in the 2007 version is the
identification and management of preoperative antiplatelet drug therapy.
"Persistent evidence supports the discontinuation of drugs that
inhibit the P2Y12 platelet binding site before operation, but there is
wide variability in patient response to drug dosage (especially with
clopidogrel)," the guidelines authors explain. "Newer P2Y12 inhibitors
are more potent than clopidogrel and differ in their pharmacodynamic
properties. Point-of-care testing may help identify patients with
incomplete drug response who can safely undergo urgent operations."
New STS/SCA Recommendations on Preoperative Interventions for Blood Conservation
Recommendation
Class of recommendation
Level of evidence
P2Y12-receptor inhibitors should be
discontinued before operative coronary revascularization (either on
pump or off pump), if possible. The optimum time between drug
discontinuation and operation will vary depending on the drug.
1
B
Point-of-care testing for platelet ADP responsiveness might be reasonable to identify clopidogrel nonresponders.
IIb
C
Adding a P2Y12 inhibitor to aspirin
therapy soon after CABG surgery may increase the risk of reexploration
and subsequent operation.
III
B
Preoperative erythropoietin (EPO)
plus iron given several days before cardiac operation is a reasonable
approach to increasing red-cell mass in patients with preoperative
anemia, in candidates for operation who refuse transfusion, or patients
at high risk for postoperative anemia. Chronic EPO may cause
thrombotic cardiovascular events in renal-failure patients.
IIa
B
Recombinant human EPO may be
considered to restore red-blood-cell volume in patients also undergoing
autologous preoperative blood donation before cardiac procedures, but
this approach has not been evaluated in large studies.
IIb
A
Ferraris acknowledged that the most current evidence on antiplatelet
therapy is always "a moving target. There are new drugs and new
evidence, and some of the new things aren't even on the market yet but
probably will be [soon]," he said. So the next iteration of these
guidelines will no doubt include even more new evidence on antiplatelet
drugs and how to use them. For example, Ferraris noted that recently
published data suggest that chronic aspirin therapy can be discontinued
earlier than five days before coronary bypass surgery without
increasing the risk of MI, death, or stroke. "But one consistent finding is that antiplatelet drugs cause excess
bleeding, and that hasn't changed with the new drugs," Ferraris told
heartwire . "The only thing that changes
is the pharmacodynamics. Some of the newer drugs have a shorter
half-life, and you don't have to wait as long to do an operation after
you stop those newer drugs, and that's a change for the better." Other additions to the guidelines that Ferraris highlighted are the
recommendations on topical hemostatic agents used during surgery to
mitigate bleeding. "There's a whole bunch of these things [on the
market], with surprisingly little evidence to support their use, but
they're widely used," Ferraris said. Topical hemostatic agents that
employ localized compression get a IIb recommendation (evidence level C)
while antifibrinolytic agents used to limit chest tube drainage get a
IIa rating (evidence level B). Also, the new guidelines recommend against using aprotinin
(Trasylol, Bayer Healthcare Pharmaceuticals), an antifibrinolytic agent,
to reduce bleeding after cardiac surgery. Bayer took the drug off the
market after it was shown that its risk outweighed its potential
benefits.
Better Format Needed for Guidelines
Ferraris
said that the writing committee is also working on finding a better
way to disseminate these guidelines and teach physicians about them
beyond just publishing them in a journal. "We'd like to find a forum
that isn't so cumbersome." For example, the STS and SCA may develop an
iPhone application or a set of flash cards to help users learn the
guidelines more easily. "One of the benefits of the guidelines is that
you find out where there is a lack of evidence or gaps in the knowledge
base, so guidelines serve to generate hypotheses about what needs to
be done next. So somehow we need to figure out how to disseminate these
more widely." References
