Table 13-10 Cardiac Risk Stratification for Noncardiac Surgical Procedures

10 Perioperative cardiac adverse event risk reduction has undergone significant changes over the past

decade. Despite these efforts, a large, international prospective study across 15,000 patients

demonstrated that more than 8% of patients undergoing major inpatient surgery still experience

postoperative myocardial ischemia.29 These patients have significantly increased 30-day mortality, even

though only 15% of perioperative ischemic episodes included typical cardiac symptoms. Previous

retrospective studies demonstrating value to coronary revascularization spurred aggressive preoperative

coronary artery disease identification and management. However, recent data have questioned the

value of coronary revascularization among asymptomatic patients in not only the perioperative period,

but also in the general medical population.30,31 The most recent American College of Cardiology

(ACC)/American Heart Association (AHA) guidelines reserve preoperative coronary revascularization

for patients demonstrating asymptomatic left main coronary artery disease, three-vessel disease,

reduced ejection fraction, unstable angina, or acute myocardial infarction.32 Furthermore, large

retrospective and prospective studies have demonstrated that the institution of perioperative betablockade also bears significant risks that must be weighed against possible benefits.33,34 As a result, the

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most recent ACC/AHA guidelines reserve the institution of beta-blocker therapy for only high-risk

patients that would warrant blockade independent of the surgical procedure.32 Patients already on betablocker therapy should be continued on the therapy throughout the perioperative period.32 The

widespread use of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, commonly

known as statins, for cardiovascular disease and hyperlipidemia has introduced another medication into

the surgical preoperative evaluation. Although prospective data establishing the value of instituting

preoperative statin therapy are limited, there is general consensus that these medications should not be

withdrawn during the perioperative period.35 A large randomized controlled trial evaluating the benefit

of other promising agents – clonidine and aspirin – as perioperative optimization standards failed to

demonstrate benefit.36,37

All patients in high-risk groups or with a history of ischemic heart disease must be evaluated and

properly treated before elective surgery. All elective surgery should be delayed for 6 months after

myocardial infarction. If this is not feasible, invasive monitoring should be considered in the

perioperative period and intensive postoperative observation should continue for at least 48 hours. The

intrusiveness of the surgical procedure also plays a part in the overall risk and need for preoperative

workup of heart disease. The AHA has produced and updated an algorithm for the recommended

preoperative workup (Algorithm 13-1).32

Percutaneous Coronary Intervention With Stenting

11 The widespread use of percutaneous intervention for coronary artery disease via stenting (with or

without drug-eluting coating) has introduced a new level of clinical complexity. In-stent thrombosis is a

feared complication with profound morbidity and mortality. Given the known proinflammatory and

prothrombotic physiologic state induced by acute illness, surgery, and anesthesia, coronary stents may

be at elevated risk for thrombosis during the perioperative period. Large retrospective studies have

demonstrated that the risk of perioperative in-stent thrombosis is increased if noncardiac surgery is

performed soon after percutaneous coronary intervention.38,39 The appropriate duration to defer

elective surgery after coronary stenting remains controversial, but recent ACC/AHA guidelines

recommend 365 days for drug-eluting stents and 30 days for bare-metal stents.32 The role for

antiplatelet therapy remains a major question, but data suggest that cessation of recommended

antiplatelet therapy in the perioperative period may have significant coronary thrombotic risks without

major improvement in bleeding adverse events.38,39 The decision to stop antiplatelet therapy prior to

recommended guidelines should be limited to specific procedures that demand a nearly bloodless

surgical field or in procedures involving closed spaces incapable of tolerating minor theoretical

increases in bleeding (intracranial, minimally invasive spine surgery). Recent data and

recommendations in the surgical literature demonstrate that continuation of aspirin therapy throughout

the perioperative period in patients with coronary artery stents should be the standard of care.32

Congestive Heart Failure

CHF has been described as the single most important factor predicting postoperative cardiac

morbidity.40 All elective surgical procedures should be deferred until heart failure is medically

optimized. If surgery cannot be deferred, aggressive perioperative management is warranted with a

goal of optimizing cardiac output. In contrast to isolated ischemic heart disease, CHF is more easily

diagnosed by history, physical examination, and basic preoperative laboratory workup, including

electrocardiography (ECG) and chest radiography. Because patients with left, right, or both left and

right ventricular dysfunction are less tolerant of the fluid shifts associated with surgery and the

myocardial depression associated with the anesthetic, they constitute the highest-risk group for

postoperative complications. Recent data demonstrate that although cardiac complications have

historically been the focus of surveillance and prevention, pulmonary and infectious complications may

warrant similar attention.41

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Algorithm 13-1. Decision aid for preoperative cardiac evaluation prior to noncardiac surgery. This decision tree for preoperative

evaluation takes into account not only the patient’s physical status but also the severity of the surgical procedure. ACC, American

College of Cardiology; AHA, American Heart Association; LOE, level of evidence.

Pulmonary Disease

Pulmonary disease is classically divided into acute and chronic restrictive and obstructive disease.

Restrictive disease is defined by processes that reduce lung volumes, and obstructive disease is

characterized by reduced flow rates on pulmonary function tests.

Obstructive diseases are present in patients with forced expiratory volume in 1 second (FEV1

)/forced

vital capacity (FVC) ratios of less than 50%. Obstructive pulmonary disease can be either chronic or

acute (asthma). In either case, the reversible component of obstruction should be reversed before

elective surgery. Patients are maintained on bronchodilator medications, and those with chronic

secretions are appropriately hydrated and receive therapy to mobilize secretions. In patients with

reactive airway disease, the endotracheal tube can induce severe bronchospasm. Even in patients who

are treated well preoperatively, reactive bronchospasm can complicate anesthetic induction and the

emergence from anesthesia. Severe bronchospasm is a life-threatening emergency that can be

challenging to diagnose and treat. Administration of potent local (albuterol) and systemic (epinephrine)

bronchodilators in a timely fashion is essential.

Regional or neuraxial anesthetics can be useful in these patients for peripheral surgery or for

procedures that require an anesthetic sensory level below T6. As the sensory and motor levels rise to T6

and above, patients lose significant accessory motor function that can decrease expiratory reserve

volume and the ability to cough and clear secretions. Because of tenuous pulmonary status and the high

incidence of postoperative pulmonary complications, these high-risk patients should be extubated with

caution only when they meet adequate extubation criteria relative to preoperative test data. Changes in

pulmonary mechanics and frequency of postoperative pulmonary complications are greatest after upper

abdominal surgery. Both vital capacity and functional residual capacity are reduced, reaching lowest

levels in the first 24 hours postoperatively. In the high-risk groups, therapy should be directed toward

restoring functional residual capacity to preoperative levels. Such therapy improves compliance and gas

exchange. Because of the potential adverse effects of systemic narcotics on respiratory drive, the use of

epidural narcotics and local anesthetics for postoperative pain control is very popular. These techniques

allow the patients to be extubated earlier and, in patients with intrathoracic and upper abdominal

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surgery, help restore pulmonary function toward preoperative values.42

Obesity

Obesity causes a host of problems on both sides of the surgical drapes. Obesity is defined as a body

mass index (BMI) greater than or equal to 30 kg/m2. BMI can be easily calculated by dividing the

patient’s weight in kilograms by the square of his or her height in meters. The pathophysiologic changes

associated with morbid obesity (BMI ≥40 kg/m2) affect the respiratory, cardiovascular, and

gastrointestinal systems. Patients have an external restrictive lung disease that reduces functional

residual capacity and worsens with the supine position. Breathing effort increases and ventilation

becomes diaphragmatic and position dependent. Increased airway pressures required to maintain

adequate ventilation in obese patients predispose this patient group to barotrauma, furthering their risk

of pulmonary complications. Obese patients frequently desaturate at night and have a high incidence of

sleep apnea. Because of increased blood volume and frequent desaturations, obese patients can develop

pulmonary hypertension and right-sided heart failure. Obese individuals have a high incidence of

coronary artery disease. Because of size alone, they have increased cardiovascular demands with limited

cardiac reserve and exercise tolerance. Obese patients have a high incidence of hiatal hernia and

gastroesophageal reflux, increasing the risk for aspiration on induction and emergence from anesthesia.

Issues as mundane as venous access can cause significant problems in this patient group.

A significant concern of the anesthesiologist is gaining adequate control of the airway. The combined

problems of aspiration risk, rapid desaturation caused by reduced functional residual capacity and

increased oxygen demand, and technical difficulties associated with intubation due to anatomic fat

deposits make intubation a high-risk procedure. If problems occur, there can be significant technical

difficulties in obtaining a rapid cricothyrotomy. For these reasons, a nasal or oral awake intubation can

be useful or even imperative. Patients should receive prophylactic administration of H2

-receptor

antagonists and a nonparticulate antacid to improve the pH of gastric contents. If intubations are to be

done after induction of anesthesia, they should be performed in a rapid sequence using cricoid pressure.

To prevent aspiration on emergence, obese patients should be extubated when fully awake, preferably

in the sitting position. Regional anesthetics can be very useful when peripheral procedures are planned.

Unfortunately, morbidly obese patients can develop pulmonary failure just by lying flat, making it

difficult to use epidural or spinal anesthetics for abdominal procedures. Epidural analgesics for

postoperative pain management allow earlier extubation and ambulation of these patients.43

Diabetes Mellitus

The incidence of DM is rising, particularly, type 2 DM in the elderly. This is a systemic disorder that has

particular relevance for the anesthesiologist and surgeon because of its effect on the vascular, renal,

nervous, and immune systems. Patients with DM should be investigated for the presence of concomitant

coronary artery disease, peripheral vascular occlusive disease, renal failure, and autonomic and

peripheral neuropathy. Problems with cardiovascular instability, fluid balance, and aspiration due to

gastroparesis should be expected. In addition, these patients are more prone to infection and have

problems with temperature control. The management of the diabetic state in these patients is important

and complicated. Hypoglycemia during the anesthetic state is a feared complication because of

challenges in prompt diagnosis. Oral hypoglycemic agents such as glipizide should be stopped prior to

surgery and hyperglycemic situations treated with short-acting intravenous or subcutaneous insulin

during the perioperative period. Insulin-dependent diabetics for same-day admission or outpatient

surgery should take one-half of their usual morning dose of long-acting insulin. After the establishment

of an IV line, laboratory blood samples are drawn and treatment of hyper- or hypoglycemia is started.

Additional insulin is then given according to the results of frequent (every 1 to 2 hours) blood sugar

monitoring. Although there are compelling data associating perioperative hyperglycemia with adverse

postoperative events, there are no randomized controlled trials demonstrating improved outcomes with

aggressive intraoperative hyperglycemia management.44 Furthermore, complications from

hypoglycemia are arguably greater than those from hyperglycemia, and are more likely as insulin

therapy becomes more aggressive during the perioperative period.

Renal Insufficiency and Failure

Because the kidneys play a vital role in metabolic, synthetic, and fluid management homeostasis, renal

failure is associated with many effects on the cardiovascular, pulmonary, hematologic, gastrointestinal,

and immune system. Pre-existing renal insufficiency is a known risk factor for postoperative myocardial

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