PRE-OP PRECAUTION Platelet testing should be a part of pre-op assessments in patients with known bleeding risks.

Controlling bleeding risks is a primary concern for surgical teams before any procedure, especially now that the patient population is getting older and presenting with more vascular disease. The challenge of limiting bleeding is compounded when patients are taking antiplatelet agents or blood thinners, including aspirin. In these cases, a personalized approach to assessing intraoperative bleeding risk is best.

Drug resistance part of the equation
Antiplatelet agents are valuable treatment options that help prevent heart attacks and strokes in patients. However, when patients require surgery, it's important to determine a course of treatment that will strike a delicate balance between minimizing bleeding risks and minimizing the risk of a cardiac event.

Many factors have to be taken into account, including the overall health of the patient, and weighing bleeding risks against the risk of the patient suffering a clot, and the likelihood of the clot being catastrophic when it forms.

If the surgery is elective, it's best to wait until the patient has been on dual antiplatelet therapy for at least 12 months. Once the patient has been stable for more than a year, the cardiologist may temporarily discontinue the antiplatelet agent and keep them on aspirin while they undergo surgery and during the very early stages of recovery.

For more than 15 years, clopidogrel (Plavix) has been one of the most widely used antiplatelet agents for patients with high-risk cardiovascular disease. In the early part of the last decade, my research team was the first to show that up to 30% of patients taking clopidogrel do not effectively respond to the drug. While our findings sparked a heated debate in the cardiology community and exposed that those not responding to the drug were at increased risk for a cardiac event (often unknowingly), it also implied that clopidogrel non-responders would not be at increased risk for bleeding during surgery, since they were not receiving the drug's anti-thrombotic benefits.

If patients are on clopidogrel, but prove to be resistant, they may be able to have surgery within 24 hours of the last dose, which has a negligible effect in about one-third of patients who take it. If you follow conventional cardiology guideline recommendations, you'd keep patients waiting for 5 days until the drug clears their systems. Surgery guidelines are a bit more progressive in attempting to keep patients from waiting, if they don't have pharmacodynamics effects from the drug.

Our research is paving the way for a more personalized approach to antiplatelet therapy, including point-of-care platelet function testing and the development of new drugs that work for patients who do not respond to clopidogrel. One new antiplatelet drug, ticagrelor (Brilinta), has proven to be pharmocodynamically effective in patients resistant to clopidogrel and offers the added benefit of a faster offset. Typically, it takes a full week for the effects of other antiplatelet agents to wear off, clearing the way for surgery. The offset of ticagrelor, a re-versible inhibitor, takes just 5 days or less.

Platelet function testing critical
Just as personalizing antiplatelet therapy may yield better patient outcomes, a personalized approach to balancing bleeding and thrombosis risks in outpatient surgery should also be considered.

Close consultation and communication with the patient's cardiologist is a key piece of this approach. Surgical guidelines say platelet function testing should be considered. It's a class 2 recommendation, which means the testing is suggested, but not mandated. The guidelines don't stipulate which method to use.

At Sinai Hospital of Baltimore, many surgeons request pre-surgical platelet function testing in patients on clopidogrel, which we are fortunate to have access to on site. Blood is obtained via veni-puncture and tested with thromboelastography, which employs analytical software to provide quantitative and qualitative measurements of a clot's physical properties. It's not a very labor intensive process, but it has to be done by technicians skilled in the practice. Results are obtained within an hour. An even easier test, Verify Now (tinyurl.com/q9gewwy), provides results in about 10 minutes, although it hasn't yet been studied prospectively.

Platelet testing may offer valuable insights into bleeding risks as well as the risk of ischemic events. If platelet reactivity is low, we tend to wait to do the surgery until the effects of antiplatelet meds fully dissipate. If platelet reactivity is high, the blood is clotting well and it's likely safe to proceed with the surgery from a bleeding perspective within 24 hours.

While point-of-care platelet function testing is being used more frequently, it has yet to become standard of care. A study conducted by my research team involving 200 patients showed that timing surgery based on the thrombolastography results of a platelet function test can reduce the surgical wait time and need for hospitalization by 50% — an important consideration for outpatient surgery facilities. Large-scale studies demonstrating that platelet function testing improves patient outcomes would lead to a paradigm shift in pre-op assessments and ultimately improve the overall quality of care for surgical patients.

Reducing risks
Developing strategies to proactively avoid excessive bleeding and thrombotic events during surgery is vitally important. Both conditions increase morbidity and mortality, but may be reduced with thoughtful planning and management, including platelet function test results and the offset effects of the antiplatelet agents the patient is taking.