Antiplatelet therapy: Nuances of perioperative antiplatelet therapy are beyond the scope of this review, but some general principles can be elucidated from the American College of Cardiology/American Heart Association (ACC/AHA) 2007 perioperative guidelines.1 Management of antiplatelet therapy should be done in conjunction with the surgical team, as cardiovascular risk has to be weighed against bleeding risk.
Aspirin therapy should be continued in all patients with a history of coronary artery disease (CAD), balloon angioplasty, or percutaneous coronary intervention (PCI), unless the risk of bleeding complications is felt to exceed the cardioprotective benefits—for example, in some neurosurgical patients.1
Clopidogrel therapy is crucial for prevention of in-stent thrombosis (IST) following PCI because patients who experience IST suffer catastrophic myocardial infarctions with high mortality. Ideally, surgery should be delayed to permit completion of clopidogrel therapy—30 to 45 days after implantation of a bare-metal stent and 365 days after a drug-eluting stent. If surgery has to be performed sooner, guidelines recommend operating on dual antiplatelet therapy with aspirin and clopidogrel.1 Again, this course of treatment has to be balanced against the risk of hemorrhagic complications from surgery.
Both aspirin and clopidogrel irreversibly inhibit platelet aggregation. The recovery of normal coagulation involves formation of new platelets, which necessitates cessation of therapy for seven to 10 days before surgery. Platelet inhibition begins within minutes of restarting aspirin and within hours of taking clopidogrel, although attaining peak clopidogrel effect takes three to seven days, unless a loading dose is used.
Beta-blockers in the perioperative setting are a focus of an ongoing debate beyond the scope of this review (see “What Pre-Operative Cardiac Evaluation of Patients Undergoing Intermediate-Risk Surgery Is Most Effective?,” February 2008, p. 26). Given the current evidence and the latest ACC/AHA guidelines, it is still reasonable to continue therapy in patients who are already taking them to avoid precipitating cardiovascular events by withdrawal. Patients with increased cardiac risk, demonstrated by a Revised Cardiac Risk Index (RCRI) score of ≥2 (see Table 1, p. 12), should be considered for beta-blocker therapy before surgery.1 In either case, the dose should be titrated to a heart rate <65 for optimal cardiac protection.1
Statins should be continued if the patient is taking them, especially because preoperative withdrawal has been associated with a 4.6-fold increase in troponin release and a 7.5-fold increased risk of myocardial infarction (MI) and cardiovascular death following major vascular surgery.2 Patients with increased cardiac risk— RCRI ≥1—can be considered for initiation of statin therapy before surgery, although the benefit of this intervention has not been examined in prospective studies.1
Amiodarone has an exceptionally long half-life of up to 142 days. It should be continued in the perioperative period.
Calcium channel blockers (CCBs) can be continued with no unpleasant perioperative hemodynamic effects.1 CCBs have potential cardioprotective benefits.
Clonidine withdrawal can result in severe rebound hypertension with reports of encephalopathy, stroke, and death. These effects are exacerbated by concomitant beta-blocker therapy. For this reason, if a patient is expected to be NPO for more than 12 hours, they should be converted to a clonidine patch 48-72 hours before surgery with concurrent tapering of the oral dose.3
Digoxin has a long half-life (up to 48 hours) and should be continued with monitoring of levels if there is a change in renal function.
Angiotensin converting enzyme inhibitors (ACEI) and angiotensin receptor blockers (ARBs) have been associated with a 50% increased risk of hypotension requiring vasopressors during induction of anesthesia.4 However, it is worth mentioning that this finding has not been corroborated in other studies. A large retrospective cohort of cardiothoracic surgical patients found a 28% increased risk of post-operative acute renal failure (ARF) with both drug classes, although another cardiothoracic report published the same year demonstrated a 50% reduction in risk with ACEIs.5,6 Although the evidence of harm is not unequivocal, perioperative blood-pressure control can be achieved with other drugs without hemodynamic or renal risk, such as CCBs, and in most cases ACEIs/ARBs should be stopped one day before surgery.