Clopidogrel (Plavix) before coronary artery bypass surgery (CABG)
significantly increases blood loss following surgery, results of a
study conducted in Canada confirm.

Clopidogrel, a potent inhibitor of platelet aggregation, is widely
used in patients with acute coronary syndromes as well as before
percutaneous coronary interventions.

However, "its favorable effects on preventing thrombus formation may
have deleterious effects on hemostasis in patients undergoing
coronary surgery," investigators note in the November Annals of
Thoracic Surgery.

To investigate, Dr. MacKenzie A. Quantz, from the University of
Western Ontario in London and colleagues prospectively assessed
hemostasis after CABG in 41 patients who discontinued clopidogrel 0
to 4 days before CABG and 39 who discontinued the drug 5 to 8 days
before surgery.

They compared the results with those of 232 patients who
discontinued clopidogrel more than 8 days before CABG or who were
never on the drug.

Most of the subjects had also received aspirin before CABG and most
were given aprotinin preoperatively, which has been shown to curb
blood loss following heart surgery in aspirin users.

Despite a higher aprotinin dose in the clopidogrel 0-to-4 day group,
this group had significantly higher postoperative blood losses in
the first 24 hours (1044 mL) relative to the 5-to 8-day group (528
mL) and the > 8-day group (573 mL).

Thirty-one (75.6%) of patients in the 0-to-4 day discontinuation
group needed blood transfusions compared with 14 (35.9%) in the 5-to-
8 day group and 98 (42.2%) in the > 8-day group (p < 0.001)

The 0-to-4 day group also required significantly more units of
transfused blood products than the other two groups and had
significantly higher rates of reoperation for bleeding.

On multivariate analysis, use of clopidogrel within 0 to 4 days of
CABG was a strong independent predictor of increased blood
transfusion requirement and prolonged ICU and hospital stay.

Based on their results, Dr. Quantz and colleagues recommend
discontinuing clopidogrel more than 5 days before CABG when possible.

In an editorial, Drs. Piet W. Boonstra and Wim van Oeveren from
Groningen University Medical Center in the Netherlands write that
this "excellent paper confirms the widespread belief among cardiac
surgeons that exposure of patients to clopidogrel in combination
with aspirin before surgery increases blood loss and blood
transfusion significantly."

Ann Thorac Surg 2004;78:1522,1536-1541