Perioperative Evaluation

Perioperative Evaluation



Christopher M. Whinney


Operative treatment of disease has a tremendous yet unrecognized impact on modern medical systems. An estimated 26 million patients underwent surgery in the United States in 2005. Serious adverse events occur in more than 1 million of these patients, at an estimated cost of $25 billion annually. With the aging population, it is anticipated that surgical referrals will increase by 25%, costs by 50%, and costs of perioperative complications by 100%. Given these staggering numbers, it is imperative that clinicians involved with patients undergoing surgery know the basics of perioperative diagnosis and management.



CARDIOVASCULAR EVALUATION AND MANAGEMENT


Cardiovascular complications are one of the most common perioperative adverse events in patients undergoing noncardiac surgery. Although in absolute numbers they are rare, they are associated with a mortality rate as high as 70%. It is essential for clinicians to be familiar with current cardiac risk evaluation and preventive strategies for patients undergoing noncardiac surgery.



PREOPERATIVE CARDIAC ASSESSMENT


The core goals of preoperative cardiac assessment are to determine the status of the patient’s cardiac conditions, to provide an estimate of risk, to determine if further testing is warranted, and to determine if interventions are warranted to reduce perioperative cardiac risk.



Prior History


The prior cardiovascular history of the patient is the foundation of the perioperative assessment. Because the incidence of perioperative cardiovascular events varies according to the patient risk profile, risk of the proposed surgery, and the patient’s functional capacity, all of these elements should be part of the preoperative history.


The clinician should inquire about prior myocardial infarction, congestive heart failure, valvular disease, angina, or arrhythmia. If the patient has had prior diagnostic testing or therapeutic interventions, inquire about when and where these were done and the results of such procedures. Traditional risk factors, such as hypertension, dyslipidemia, tobacco use, and diabetes, are essential elements, as well as comorbid conditions that might limit functional capacity such as peripheral vascular disease, chronic obstructive pulmonary disease, cerebrovascular disease, and renal insufficiency. Current symptoms such as chest pain at rest or on exertion, shortness of breath, claudication, syncope or presyncope, or anginal equivalent symptoms should be noted.


Functional capacity is vital information, because exercise capacity is a reliable predictor of future cardiac events. This is usually expressed in metabolic equivalents (METs), where one MET is defined as the oxygen consumption of a 70-kg man at rest. Greater than 7 METs of activity tolerance is considered excellent, whereas less than 4 METs is considered poor activity tolerance. The Duke Activity Status Index suggests questions that correlate with METs levels; for example, walking on level ground at about 4 miles per hour or carrying a bag of groceries up a flight of stairs expends approximately 4 METs of activity. Patients limited in their activity from noncardiac causes, such as severe osteoarthritis or general debility, are categorized as having poor functional capacity, because one cannot discern if significant cardiac conditions exist without the benefit of noninvasive cardiac testing.


The degree of surgical risk contributes to a patient’s risk for cardiac complications. In general, procedures that are longer and have greater potential for blood loss, hemodynamic instability, and intravascular fluid shifts carry greater risk. Procedural risk is stratified into high (estimated mortality >5%), intermediate (mortality 1%-5%), and low (<1%) risk categories. Vascular surgery procedures are considered high risk procedures, with the exception of carotid endarterectomy; the literature cites an event rate between 1 and 5% for this procedure, categorizing it as an intermediate-risk operation.


The physical examination serves to confirm the above information and can reveal information of importance unknown to the patient. Vital signs can detect hypertension or hypotension, tachycardia or bradycardia, significant arrhythmias, or hypoxia if pulse oximetry is used. Jugular venous distension, the presence of an S3 gallop, or rales suggest decompensated heart failure. Cardiac murmurs should be noted, especially if aortic stenosis is suspected. Carotid, femoral, or abdominal bruits suggest the presence of peripheral vascular or cerebrovascular disease.


The electrocardiogram is a commonly used tool in traditional preoperative cardiac assessment, although its role in the asymptomatic patient is unclear. Incidental findings that might be significant include evidence of prior myocardial infarction (MI), conduction abnormalities such as second- or third-degree heart block, bundle branch block, and left ventricular hypertrophy suggesting hypertensive heart disease. Although the current literature notes no evidence that asymptomatic findings on the preoperative EKG affect postoperative cardiac risk, clinicians often obtain this test as a preoperative baseline for comparison in the patient with prior heart disease or with significant clinical predictors for cardiovascular events.



Risk Stratification


Since Goldman and colleagues created the first risk-stratification tool in the late 1970s, several risk indices have been published, each with their own benefits and limitations. The most prominent in use are the guidelines published jointly by the American College of Cardiology and the American Heart Association, (the ACC/AHA guidelines), most recently revised in September 2007. The stepwise risk assessment recommended by the ACC/AHA is demonstrated in Figure 1. This revision incorporates a simple, validated assessment tool called the Revised Cardiac Risk Index (RCRI). The RCRI discerns the presence of six independent predictors of major cardiovascular complications (Box 1). The authors of this tool did not make recommendations for risk reduction, but subsequent studies suggest the use of beta blockers based on RCRI score results.


image image

Figure 1 Cardiac evaluation and care algorithm for noncardiac surgery based on active clinical conditions, known cardiovascular disease, or cardiac risk factors for patients 50 years of age or older.


Consider perioperative beta blockade for populations in which this has been shown to reduce cardiac morbidity/mortality. *Clinical risk factors include ischemic heart disease, compensated or prior heart failure, diabetes mellitus, renal insufficiency, and cerebrovascular disease. ACC/AHA, American College of Cardiology/American Heart Association; HR, heart rate; LOE, level of evidence; MET, metabolic equivalent.


(Reproduced with permission from Fleisher LA, Beckman JA, Brown KA, et al: ACC/AHA 2007 guidelines on perioperative cardiovascular evaluation and care for noncardiac surgery: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the 2002 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery). Circulation 2007;116:e418–e499.)



Box 1 Revised Cardiac Risk Index Criteria


Adapted from Lee TH, Marcantonio ER, Mangione CM, et al: Derivation and prospective validation of a simple index for prediction of cardiac risk of major noncardiac surgery. Circulation 1999;100(10):1043-1049.



High-risk surgical procedure, defined as intraperitoneal, intrathoracic, or suprainguinal vascular procedure

Ischemic heart disease, defined as the following:
• History of myocardial infarction

• History of or current angina

• Use of sublingual nitroglycerine

• Positive exercise test results

• Q waves on electrocardiogram

• Patients who have undergone percutaneous transluminal coronary angioplasty or coronary artery bypass graft surgery and who have chest pain presumed to be of ischemic origin

Cerebrovascular disease, defined as the following:
• History of transient ischemic attack

• History of cerebrovascular accident

Diabetes mellitus requiring insulin therapy

Chronic renal insufficiency, defined as a baseline creatinine level of at least 2.0 mg/dL (177 µmol/L)


Noninvasive Testing


In patients with suspicion for occult coronary artery disease or with risk factors and limited functional capacity, noninvasive cardiac testing can further unveil the presence of significant coronary artery disease and assess the patient’s functional capacity. Treadmill stress testing, with and without thallium imaging, has been assessed in the literature and found to have excellent negative predictive value for perioperative cardiac events. Dipyridamole or adenosine thallium imaging can be used in patients unable to reach an adequate heart rate with physical activity and also has a comparable negative predictive value. In addition, dobutamine echocardiography has similar efficacy in risk stratification, with the added advantage of lower cost; this test is more limited in patients with preexisting wall motion abnormalities or in the presence of bundle branch blocks. Trans-thoracic echocardiography may be helpful if congestive heart failure (CHF) or significant valvular disease is suspected (ejection fraction <35% has been shown to predict postoperative CHF), but this should not be pursued for screening purposes. Although these tests have good negative-predictive value, they have poor positive-predictive value for perioperative cardiac events; thus, a positive test is more limited in its value.



Coronary Artery Revascularization


If significant coronary artery disease is seen by noninvasive testing or by cardiac catheterization, options for management include medical optimization or revascularization. Asymptomatic patients with prior coronary artery bypass graft (CABG) surgery or percutaneous coronary interventions have lower rates of perioperative mortality and nonfatal myocardial infarction (MI) compared with historical controls; this protective effect lasts approximately 4 to 6 years. However, studies such as the CARP and DECREASE-V trials suggest that prophylactic revascularization, even in high-risk surgeries, provide no risk reduction in patients without unstable symptoms. This may in part be due to the risks of the revascularization itself (CABG surgery complications or stent thrombosis). If patients have an independent indication for revascularization, this should be pursued and elective surgery should be postponed; otherwise, medical optimization should be considered as the primary means of risk reduction.



Perioperative Risk Reduction


Medical means of perioperative cardiac risk reduction in recent times have predominantly focused on two classes of medications: selective β1 antagonists (beta blockers) and 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins).


Beta blockers are well established to reduce cardiac mortality, MI, and ischemia in ambulatory settings; four studies between 1996 and 2001 found that perioperative beta blockade reduced the risk of death, MI, or both between 50% and 90% at postoperative intervals from 28 days to up to 2 years. Subsequent randomized, controlled trials of vascular surgery patients showed no clear benefit from metoprolol on major cardiac events; a meta-analysis by Devereaux and colleagues of the trials showed a small benefit on 30-day adverse outcomes that failed to reach statistical significance. A retrospective review by Lindenauer and coworkers that evaluated data on more than 600,000 patients extracted from Medicare databases used the RCRI score and found that low-risk patients (RCRI = 0) did not benefit and might actually have been harmed by beta blockade, but higher risk patients (RCRI ≥3) had significant risk reductions for in-hospital death.


The recently published POISE trial was a randomized, controlled trial of more than 8000 patients spanning 21 countries comparing extended-release metoprolol with placebo. Metoprolol administration reduced the risk of nonfatal myocardial infarction, cardiac revascularization, and clinically significant atrial fibrillation 30 days after randomization compared with placebo. However, the beta-blocker group suffered a significantly higher risk of overall mortality, stroke, and clinically significant hypotension and bradycardia. Criticisms of the trial methodology included the high dose of beta blocker used (100 mg preoperatively followed by 200 mg daily postoperatively as tolerated hemodynamically) and the lack of dose titration; however, this is the largest randomized trial of perioperative beta blockade to date, and it suggests that harm might outweigh benefit. Further studies are needed to define more clearly the population who will benefit from prophylactic beta blockade, as well as the optimal regimen in both dose and timing. The algorithm suggested by Auerbach and Goldman for selecting patients for beta blockade (Fig. 2) is still a reasonable method to use until further trial data are available.


image

Figure 2 Suggested algorithm for perioperative of beta blockers.


CAD, coronary artery disease; PVD, peripheral vascular disease; RCRI, Revised Cardiac Risk Index.


(From Auerbach AD, Goldman L: β-Blockers and reduction of cardiac events in noncardiac surgery: Clinical applications. JAMA 2002;287[11]:1445-1447.)


Statin therapy has been evaluated in the perioperative setting by observational studies by Poldermans and colleagues and by Kertai and colleagues and by a small randomized trial by Durazzo and coworkers. These studies consistently reveal 60% to 70% reduction in mortality in patients taking statins. Because patients at risk for postoperative MI and cardiac events often have indications for statins, the perioperative period may be an opportunity to start appropriate statin therapy in these patients.

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Jul 18, 2017 | Posted by in GENERAL SURGERY | Comments Off on Perioperative Evaluation

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