Antiplatelet Therapy Continuation in Spine Surgery - Its Effect on Postoperative Morbidity and Mortality

BACKGROUND Antiplatelet agents (APAs) are widely prescribed for coronary stenting, primary and secondary prevention of cerebrovascular and coronary artery disease. Dual antiplatelet therapy (aspirin/plavix) has become the mainstay antiplatelet treatment strategy for the prevention of stent thrombosis. Maintaining antiplatelet therapy until the end of the indicated period is crucial for the success of coronary stents. Premature discontinuation of antiplatelet therapy markedly increases the risk of stent thrombosis, a catastrophic event that frequently leads to myocardial infarction (MI), with a death rate of 20-40%. Aspirin is commonly prescribed for lifetime in patients at increased atherothrombotic risk, whereas Plavix is regarded as mandatory until the coronary stents are fully endothelialized, which takes 4-6 weeks for bare metal stents and up to 1 yr for drug-eluting stents. And yet, within the first year after stenting, approximately 5% of patients who have undergone percutaneous coronary interventions (PCIs) will require noncardiac surgery, thus raising dilemmas of APA management: stopping APA treatment before operation to avoid bleeding while risking postoperative stent thrombosis versus maintaining APA therapy perioperatively thus risking extensive blood loss but limiting the risks of postoperative ischemic events.

Current recommendations are that aspirin should not be discontinued pre-operatively, with the exception of brain surgery and certain urological operations in which bleeding may be difficult to control and is therefore life threatening.

The continued use of plavix during the perioperative period significantly increases intraoperative blood loss, re-operations for the control of hemorrhage and transfusions, but does not affect morbidity, mortality, or surgical outcomes.

Most guidelines recommend to postpone invasive procedures until the end of the indication for plavix. Only vital or emergency surgery should be performed on full antiplatelet therapy, with the exception of procedures in which even a small hemorrhage may have disastrous consequences (e.g. intracranial surgery, spinal surgery in the medullary canal, surgery of the posterior chamber of the eye), or procedures involving massive bleeding.

Evidence-based data are needed to guide management of patients in whom early antiplatelet withdrawal is being considered (e.g. those who require non-cardiac surgery). Several studies have been conducted in orthopedic and cardiac surgery, however, to the best of our knowledge, not in spine surgery. This type of surgery might often be semi-urgent and postponing surgery for long time may be problematic.

This prospective, observational study is designed to evaluate the safety of APA therapy continuation in patients admitted for lumbar spine surgery.

METHODS

Study design The study will be conducted as an observational one. An informed consent will be obtained from all patients matching the above criteria. Diuretics and oral hypoglycemics will be discontinued the day prior to surgery, as dictated by the routines in our patients. Antiplatelet therapy will be continued as commonly practiced in these procedures. Any deviation from this protocol will be documented. Throughout the postoperative period study patients will be observed for any bleeding- or thrombosis-related events, and relevant perioperative data will documented (see "patient monitoring \& assessment").

Peri-operative management Anesthetic and surgical management, including management of surgical hemorrhage or any other hemodynamic event will adhere to standard practice. Postoperatively, study patients will be transferred to the post-anesthesia care unit and later to the neurosurgery department, unless otherwise indicated. In the postoperative period, departmental routines will guide blood product transfusions, pain management, fluid regimens and medications administered.

Patient monitoring \& assessment

Patients will be allocated into 4 groups:

1. Patients not at risk of coronary and/or cerebrovascular disease, and not taking APAs.
2. Patients at high risk for cardio/cerebrovascular disease (diabetes mellitus, cigarette smoking, hypercholesterolemia, hypertension, morbid obesity), but not taking APAs.
3. High-risk patients with cardiovascular risk factors (as above), in whom APA is prescribed as primary prevention of coronary artery disease (CAD).
4. Patients with a history of a coronary syndrome (stable/unstable angina); MI; transient ischemic attack (TIA)/stroke; severe carotid artery stenosis/stenting; or peripheral vascular disease, on APAs for secondary prevention.

For each consented patient included in the study we will record demographics and medical history ; chronic medications ; detailed cardiovascular history ; neurological examination ; APA-related data: type and dose of APA taken; indication ; Intra-operative data ; and perioperative complications.

Outcome measures

1. Primary outcomes: hemorrhagic, thrombotic, and neurological complications Include any complication, morbidity or death potentially caused by continuation (e.g., direct or indirect hemorrhage; hemorrhagic CVA) or withdrawal of APA therapy (e.g., MI; PE; ischemic CVA; DVT; etc.), occurring until discharge, or within 30 postoperative days. Neurological complications may be related to surgery; bleeding; thrombosis; other, and will be classified accordingly.
2. Secondary outcomes Include: re-intubations; transfer to ICU; length of stay (LOS); re-admissions within 7 / 30 days; major morbidity or death 30 and 60 days postoperatively.

Study size The study is expected to last 2 years, and to include approximately 200 patients.

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