Author(s): Ann Norris, James Taylor Lloyd
Patients undergoing vascular surgery frequently have multiple comorbid conditions that should be optimized prior to surgery.
Cardiovascular system. Major adverse cardiac events (MACE) such as stroke, myocardial infarction (MI), cardiac arrest, and death are the leading cause of morbidity and mortality in patients undergoing vascular surgery. MI accounts for about one-half of early postoperative deaths. Accurate risk stratification based on preoperative patient characteristics remains a significant challenge in vascular surgery. Commonly used risk calculators such as the Revised Cardiac Risk Index (RCRI) and Gupta Myocardial Infarction or Cardiac Arrest have reduced performances in vascular surgery. Alternate scoring systems such as the Geriatric-Sensitive Perioperative Risk Calculator, Vascular Surgery Group of New England Cardiac Risk Index, and Vascular Quality Initiative Cardiac Risk Index tools have been proposed to address these shortcomings, but have their own limitations. Below are some specific considerations with regard to vascular surgical patients.
Cardiac stress testing. For nonemergent cases, in patients estimated to be at elevated risk (>1% risk of perioperative MACE) with poor functional capacity (<4 METS), noninvasive cardiac stress testing should be carried out if the results will impact patient care. Dobutamine stress echocardiography or myocardial perfusion imaging will be necessary for patients with physical limitations such as claudication or disability from prior stroke. The need for coronary artery catheterization is determined based on the results of the stress test.
Echocardiography may be indicated if the patient has a new murmur, dyspnea of unknown etiology, valvular heart disease, or heart failure with new or worsening symptomatology.
Cardiac Biomarkers such as beta-natriuretic peptide (BNP) to aid in preoperative risk stratification are not currently part of the American College of Cardiology guidelines but have been integrated into society guidelines in Europe and Canada. Several studies have shown an association between elevated preoperative BNP and adverse cardiovascular events in noncardiac surgery, though optimal cutoff levels or a precise algorithm for how to respond to elevated levels have not been well defined. Cardiac biomarkers represent a potential emerging area to further improve preoperative risk stratification, particularly in vascular surgery patients where the RCRI has not been shown to be as predictive.
Blood pressures should be measured in both arms to determine whether there is a difference. Due to the systemic nature of atherosclerosis, patients may have subclavian or axillary arterial stenoses. Blood pressure should be monitored in the extremity with the higher reading.
Coronary revascularization should be carried out only if medically indicated. According to the Coronary Artery Revascularization Prophylaxis trial, coronary revascularization in advance of major vascular surgery has not been shown to improve outcome when compared with medical management. This trial excluded patients with left main coronary artery disease, ejection fraction less than 20%, and severe aortic stenosis.
β-Blocker therapy should be maintained in patients already on chronic therapy. Initiation of β-blocker therapy is reasonable in patients with three or more RCRI risk factors or in patients with reversible ischemia on preoperative testing. However, improper timing and dose titration may increase risk of stroke and mortality. β-Blocker therapy should be started at least 2 days prior to surgery; 7 days is preferred. Therapy should be started at a low dose and titrated slowly to achieve target heart rate of 60 to 80 bpm and should be held for hypotension.
Antiplatelet therapy.Aspirin therapy should be continued in patients with coronary stents, cerebrovascular disease, or high-risk coronary artery disease. Continuation should be considered in all vascular surgical procedures in discussion with the surgical team. Aspirin therapy is associated with an increased risk of bleeding. POISE-2, a randomized, controlled trial of 10,000 patients undergoing noncardiac surgery, did not show a benefit of aspirin initiation or continuation with respect to MACE or death. However, it excluded patients who had recently received coronary stents and those undergoing carotid endarterectomy (CEA). Furthermore, only a small proportion of the study population underwent vascular surgery. Continuation of clopidogrel therapy depends on patient factors (eg, presence and type of coronary stents and when they were placed) as well as surgical factors.
Statins should be continued perioperatively. The initiation of statin therapy is reasonable in patients undergoing vascular surgery. The statin should ideally be started 1 week to 30 days prior to the surgical procedure. There is evidence that statins decrease coronary inflammation regardless of low-density lipoprotein level. Withdrawal prior to surgery has been associated with increased cardiac events.
Warfarin, depending upon the indication and in consultation with the surgical team and prescribing provider, should be discontinued at least 3 to 5 days before surgery, and heparin therapy initiated.
If regional anesthesia is planned, anticoagulant and antiplatelet agents should be held according to the most recent American Society of Regional Anesthesia (ASRA) guidelines and in consultation with the surgeon and cardiologist.
Respiratory system. Many vascular patients have histories of significant tobacco use and may have compromised pulmonary function (see Chapter 4: Specific Considerations With Pulmonary Disease). Routine pulmonary function testing is not indicated. Aortic cross-clamping and associated ischemia-reperfusion can produce a systemic inflammatory response that may contribute to postoperative lung injury.
Renal system. Preexisting renal dysfunction is common. It is related to atherosclerosis, hypertension, diabetes, and advanced age and may exist even in the absence of an abnormal serum creatinine value. These patients have a reduced capacity to autoregulate renal perfusion in the setting of hypotension and are often intolerant to perioperative insults such as ischemia-reperfusion, atheroembolism, and nephrotoxins like contrast dye. Patients with chronically elevated serum creatinine levels (>2 mg/dL)
have substantially greater morbidity and mortality following vascular surgery. Open aortic and renal arterial surgeries carry the highest risk for postoperative renal dysfunction. Patients undergoing endovascular procedures are at risk for contrast-induced acute kidney injury (CI-AKI). CI-AKI is diagnosed by an increase in serum creatinine beginning 24 to 48 hours following contrast exposure in a patient with no other reason for AKI. In otherwise healthy patients, the risk of CI-AKI is low and its clinical relevance is debated. The risk of CI-AKI is increased in patients with chronic kidney disease, diabetes, anemia, heart failure, and hemodynamic instability. Procedures using high-osmolar contrast or high volumes of contrast are higher risk. In patients at risk, crystalloid administration and the use of low volumes of iso-osmolar or low-osmolar contrast agents are recommended. Treatment with sodium bicarbonate and N-acetylcysteine (NAC) has also been used to prevent CI-AKI. However, results of the PRESERVE trial demonstrated neither a benefit of sodium bicarbonate over saline nor a benefit of NAC over placebo in preventing AKI.Central nervous system. Patients should be examined for carotid bruits and questioned for a history of transient ischemic attacks (TIAs) and cerebrovascular accidents. Symptomatic carotid disease may warrant revascularization prior to other elective procedures.
Endocrine system. In addition to accelerated atherosclerosis, patients with long-standing diabetes may have extensive microvascular disease resulting in autonomic dysfunction, silent myocardial ischemia, and nephropathy. In consultation with the patient’s endocrinologist, metformin should be discontinued prior to procedures that involve intravenous (IV) contrast dye or renal or hepatic ischemia due to the potential for the development of severe lactic acidosis. It should also be held in patients with preexisting renal dysfunction or heart failure.
Glucagon-like–peptide 1 (GLP-1) agonists are increasingly being prescribed for type 2 diabetes, cardiovascular risk reduction, and weight loss. These medications are associated with delayed gastric emptying and have been linked to cases of aspiration. Current American Society of Anesthesiologist (ASA) recommendations are to hold these medications on the day of surgery for patients taking GLP-1 agonists daily and the week prior to surgery for patients taking them weekly. Patients requiring surgery who have not held this medication appropriately should be managed as having a full stomach.
Sodium glucose co-transporter 2 (SGLT-2) inhibitors are another emerging medication with indications for diabetes, heart failure, and renal failure. SGLT-2 inhibitors are associated with euglycemic diabetic ketoacidosis (DKA), a process of ketosis characterized by normal or mildly elevated blood glucose and an anion-gap metabolic acidosis. Surgical stress can exacerbate the risk of euglycemic DKA and thus it is recommended to discontinue SGLT-2 inhibitors 3 to 4 days prior to surgery. Laboratory values (pH, bicarbonate, anion gap, beta-hydroxybutyrate) should be closely monitored in patients who haven’t appropriately discontinued these medications preoperatively or in patients who develop otherwise unexplained metabolic acidosis during the intraoperative or postoperative period.
Hematologic system. The vascular surgical patient is at particularly high risk to develop heparin-induced thrombocytopenia (HIT) due to the need for repeated and occasionally prolonged exposure to heparin (see Chapter 24: Anesthesia for Spine Surgery). This syndrome is characterized by thrombocytopenia and/or thrombosis in the setting of heparin exposure and is due to the formation of antibodies to the heparin–platelet factor 4 (PF4)
complex. The 4T score helps determine the pretest probability of a HIT diagnosis and should guide clinical management (eg, suspension of heparin administration if the probability is intermediate or high). The acute management of the patient with HIT includes discontinuation of all heparins, suspension of warfarin, avoidance of platelet transfusions, and the initiation of alternative, nonheparin anticoagulant therapy.In patients with active HIT alternative anticoagulation with direct thrombin inhibitors such as argatroban and bivalirudin can be used. These medications are only FDA approved for use as an anticoagulant during percutaneous coronary intervention but bivalirudin has also been studied for use during cardiopulmonary bypass. Argatroban’s effect can be monitored intraoperatively using activated clotting time (ACT). There is no currently approved method to monitor the effect of bivalirudin but ACT and activated partial thromboplastin time (aPTT) have been used. These alternative anticoagulants carry an increased risk of bleeding due to the lack of a reversal agent. In addition, bivalirudin is renally cleared and its elimination can be delayed in patients with renal dysfunction. Argatroban is hepatically cleared and similarly can have decreased elimination in patients with hepatic dysfunction.