Limitations
The main limitations of the current study are the retrospective nature
of the study, with most cases performed by a single surgeon, and the
population sample not being random, although it did include all isolated
primary CABG patients during the 2 study periods. In addition, the
protocol was implemented as a unit, so we could not analyze which
techniques were more successful than others. For example, several of the
protocol measures, such as cessation of blood thinners and use of
aminocaproic acid and cell saver, were part of our practice to varying
degrees during the first study period because their efficacy in reducing
transfusions had been previously proven. The purpose of the protocol was
to reduce transfusion rates, with the understanding that some variables
could be more impactful than others. The study did not test any of these
variables independently. However, a major change during the second
period was tolerance of anemia both intraoperatively and
postoperatively. Commonly, during the first period (group A), the
hematocrit “trigger point” for transfusion was 26% compared with 21%
for the second period (group B).
Some may argue that this study was underpowered to demonstrate improved
outcomes from a restrictive transfusion protocol. First, the low risk of
blood transfusion-related complications would require a much larger
sample to demonstrate any meaningful difference. Second, outcomes
typically measured with coronary revascularization would not necessarily
capture some of the potential long-term transfusion-related
complications. Third, the purpose of this study was to demonstrate the
feasibility and safety of implementing a transfusion reduction practice
in one of the most commonly performed cardiac operations, not to prove
or disprove the risks of blood transfusions already well documented in
the literature. Finally, there is a fundamental flaw with such an
argument. When subjecting a patient to a treatment or intervention, the
burden of proof should be on the intervening rather than the
non-intervening group. To our knowledge, there are no studies
demonstrating improved outcomes with transfusions. Should patients
undergo an operation or receive chemotherapy with no proven benefit?
Blood products are a scarce resource,31,32 and
exhausting them without a proven justification in an era of
evidence-based medicine imposes a moral question. Should we transfuse a
stable patient post-CABG merely for a predetermined hematocrit trigger
point, while it could be life saving for another patient?
Two key issues are at hand. First is the realization and acceptance of
the team caring for the patient that a blood transfusion does not lead
to better outcomes and may actually be detrimental. Second, and perhaps
more challenging, is taking ownership and interest in reducing blood
use. This would require buy-in from all team members. At our facility,
the primary caretaker is the surgeon, who must approve or deny all
transfusion requests. This could be more challenging in other settings
with multiple services (such as intensivists, residents, etc.),
mandating strict adherence to a protocol agreed on by all.