Many patients are on aspirin for its antiplatlet effects. If the patient is on low dose aspirin then this potentially increases the risk of bleeding complications. If possible aspirin or the anti-platelet drug should be discontinued ten to eleven days prior to surgery. (It takes that long to make new platelets).
Plavix is a more potent anti-platelet drug than aspirin.
Note that vascular patients need their aspirin; aspirin should not be discontinued prior to vascular operations.