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  Perioperative risk assessment by careful history, physical examination, and selective investigation is essential for directing therapy in the high-risk surgical patient.

  
  
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  To decrease mortality and morbidity, major medical illnesses must be identified and appropriately managed.

  
  
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  Delirium is a common postoperative complication that can be anticipated given risk factors.

  
  
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  Perioperative cardiac morbidity can be minimized with preemptive medical management which includes the perioperative administration of β-blockers in very select patients.

  
  
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  Postoperative pulmonary complications can be reduced by aggressive pre- and postoperative care.

  
  
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  Diabetes mellitus and steroid dependence must be completely managed to significantly influence perioperative morbidity and mortality.

As indicated in Chap. 110, surgery and anesthesia trigger a host of physiologic responses. Anesthesiologists have described elective surgery as “planned trauma.” Thus they prepare for all the traumatic sequelae that will occur such as blood loss and fluid shifts, increased myocardial oxygen demands, respiratory changes caused by intubation and ventilation with supplemental oxygen, increased plasma cortisol of the stress response, and coagulopathy to name a few. In the average otherwise healthy patient, these responses result in no major untoward postoperative events. However, in the medically compromised patient, the additional burden of surgical stress can prove to be very challenging and sometimes insurmountable. Such patients frequently require detailed evaluation and monitoring in the preoperative as well as postoperative periods in the intensive care unit (ICU). Careful planning, preoperative assessment, and management of identified abnormalities in these patients are crucial to optimize chances of a good postoperative outcome. A major component of this planning involves the assessment of risks for intraoperative and postoperative morbidity. Patients with cardiac, respiratory, and renal abnormalities pose special risks for postoperative complications. In this chapter, we present guidelines for identifying and managing patients at risk of developing postoperative morbidity.

Table 111-1 is a system of perioperative screening for patients at St Michael’s Hospital in Toronto, Canada. Patients identified preoperatively with severe disease (Table 111-1) or gravid patients for nonobstetric surgery should be seen by an anesthesiologist in an outpatient clinic where there is time for preoperative risk stratification and disease optimization if possible. If conditions are found that warrant a delay in surgery, early identification minimizes the impact of other scheduled surgeries. At that juncture, additional advice from Internal Medicine or medical subspecialties is sought as necessary for postoperative management.

Codifying or classification leads to more rapid and precise communication among clinicians: shock classification, solid organ injury grading, and subarachnoid hemorrhage classification are such examples. The American Society of Anesthesiologists (ASA) physical status classification was created with a similar goal (Table 111-2) and is still commonly used as an index of surgical risk.¹ The Dripps-American Surgical Association classification is essentially identical.² Not surprisingly, for a nonparametric scale, morbidity and mortality do not rise regularly with increasing score. The risk for anesthesia and surgery for ASA 1-2 patients is thought to be better than 1:50,000. The risk rises acutely for ASA 4 but is not 100% for ASA 5!³ Additionally, statistics are made more difficult to interpret as the score is assigned by a clinician who is free to interpret “constant threat to life.” A patient critically dependent on dialysis may logically be called ASA 4 but such patients have competed in triathlons.⁴ Therefore, clinicians should not depend entirely on such scales for risk assessment but critically assess the individual.

Delirium is a common postoperative complication. As discussed in Chap. 82, patients cared for in critical care areas can suffer rates nearing 80%. Delirium in elderly postoperative patients is thought to have a 50% occurrence.⁵ Longitudinal studies have demonstrated long-term cognitive dysfunction in patients who have suffered delirium as inpatients.⁶

The risk factors for delirium are numerous and include the trauma of surgery and anesthesia (Table 111-3). Strangely enough, patients who have received regional anesthetics, thus likely exposed to less opiates, have the same rate of delirium as similar patients who have undergone general anesthetics.⁷ Other factors common to our aging population such as structural (stroke, brain injury) and nonstructural (psychiatric) brain disease increase the risk for delirium. Knowing that a patient may suffer postoperative delirium allows treatment to commence immediately.

Postoperative pain is a very important risk factor for the development of delirium. Patients may enter a terrible feedback loop of suffering from delirium only to have opiates removed from their postoperative regime to then experience more pain and more delirium! The phenomenon of patients receiving inadequate pain control is even more important in the critical care units where reliance on propofol sedation without concomitant analgesia gives rise to a calm appearing patient. Given that many ICUs do not have a formal sedation and analgesia protocol, which includes sedation and analgesia goals, patients risk being sedated without analgesia.⁸ These patients are at high risk for postoperative delirium.

Postoperative delirium requires a multimodal treatment strategy. While haloperidol is sometimes considered,⁹ the evidence for improved outcomes in those treated with this medication is lacking. Pretreating patients at risk for delirium has had limited success.¹⁰

Identifying at risk patients allows the surgeon caring for postoperative patients to reduce the risk for delirium. This is done by ensuring that environmental, medical, and pharmacological factors favor recovery. Examples of such measures include ensuring the patient has appropriate vision and hearing aids in place, controlling noise and lighting that affect sleep-wake cycles, ensuring adequate pain control, treating of dehydration, appropriate nutrition, and avoiding polypharmacy.

Our aging population, rising rates of obesity, and type II diabetes suggest that more patients presenting for noncardiac surgery will have diagnosed or clinically suspected ischemic heart disease and thus increased risk for perioperative complications. Using multivariate analysis of 1001 consecutive patients presenting for noncardiac surgery, Goldman and associates developed an index for perioperative risk (cardiac risk index) based on clinical, electrocardiographic (ECG), and routine biochemical parameters.¹¹ The strongest predictors of cardiac morbidity were the severity of coronary artery disease, a recent myocardial infarction (MI), and perioperative heart failure. Detsky and coworkers reworked the scoring system to allow for broader applicability and less dependence on clinical examination findings.¹² At present, the standard for perioperative cardiac risk assessment combines surgery specific risk, the Eagle criteria¹³ (Table 111-4), and medical risk (Revised Lee cardiac risk index).¹⁴ The Lee index also includes surgical risks as one of the variables, however only considers suprainguinal vascular surgery to be high risk as opposed to Eagle who considers all vascular surgery risky. Low risk is defined as less than 1% possibility of perioperative cardiac complications. High-risk patients have a predicted risk of greater than 10%.

In 2007, the American College of Cardiology and the American Heart Association published their guidelines for preoperative assessment.¹⁵ The guidelines were quickly updated only 2 years later to reflect new perioperative β-blockade information.¹⁶

Their conclusion was that patients in the low-risk category may proceed directly to surgery with an expectation of a low rate of cardiac complications. Clearly, patients who require emergent surgery should proceed immediately to the operating theatre without delay for cardiac testing. Patients deemed to be in the high-risk group (those who suffer from unstable coronary artery disease [CAD], decompensated congestive heart failure [CHF], severe valvular disease, and unstable arrhythmias) should have their noncardiac surgery delayed for full cardiac evaluation and treatment.

It is the group of patients in the intermediate risk category who will benefit most from the investigations described below, in an effort to further elucidate the extent of their underlying cardiac disease and to attempt to quantify and possibly reduce the perioperative risks before the commencement of the surgical procedure.

Testing becomes more important as patients face intermediate- or high-risk surgery without good preoperative functional capacity. Patients who suffer from functional limitation due to surgical disease may mask important cardiorespiratory disease. In addition, North America and many other Western countries are in the midst of an obesity epidemic. The US Department of Health and Human Services suggests that most American citizens lead sedentary lives. Forty percent of survey respondents do no leisure physical activity whatsoever. The lack of symptoms in this large segment of the population results from “auto–β-blockade.” The patient never achieves in their activities of daily living enough physiologic challenge to reveal their disease.

Without symptoms of CHF, the possibility of complete left ventricle (LV) systolic decompensation is low. Routine LV function studies by echocardiography are contraindicated. The question remains: “Does this patient have ischemic risk?” In the setting of patients who cannot exercise or do not have the physical fitness needed for exercise stress testing, the ACC/AHA suggest nuclear medicine perfusion studies or stress echocardiography. Both studies also offer the clinician insight into LV function.

The increasing availability of echocardiography has allowed the diagnosis of valvular disease at a rate much higher than in the era of Goldman and Detsky where clinical examination findings defined risk. An increasingly mobile global population results in the presentation of diseases such has rheumatic mitral stenosis, considered uncommon to Western-born patients. Recent publications on perioperative antibiotic coverage have addressed the evolving science of endocarditis prevention. In 2006, the enigma of “mitral valve prolapse without mitral valve regurgitation” was a Class III recommendation for antibiotics.¹⁷ The update that followed 2 years later concluded even more strongly that there were no Class I indications for endocarditis prophylaxis.¹⁸ The committee did recognize that in certain very high-risk populations (previous endocarditis, prosthetic heart valves, valvulopathy following cardiac transplantation, and certain congenital heart disease patients) antibiotic prophylaxis “would be reasonable” but with a weaker IIa recommendation. The highest risk of bacteremia is attributed to dental surgery or surgery with gingival manipulation. Endoscopy was considered low risk.

PREOPERATIVE CORONARY REVASCULARIZATION

One would expect that if a patient who faces high-risk noncardiac surgery is known to have coronary artery disease, revascularization should improve outcome. Early recommendations for preoperative coronary artery bypass grafting (CABG)¹⁹ were based on retrospective data, and either utilized historical controls or did not include the mortality associated with CABG itself. Recently, several trials have examined revascularization through percutaneous procedures as well as sternotomy. The CARP trial randomized over 500 patients to have coronary revascularization or not prior to elective surgery.²⁰ There were no differences between groups in terms of short-term or long-term outcome. This was followed by other trials which attempted to address some relative weaknesses of CARP and drew the same conclusions. It is difficult to dispute that if the patient has an independent reason for urgent coronary revascularization such as left main coronary artery disease or continued ischemia following myocardial infarction, coronary revascularization should precede elective noncardiac surgery. Present evidence would suggest that if important but noncritical coronary artery disease is identified, preoperative revascularization will delay access to noncardiac surgery without definite benefit. In the setting of oncologic surgery and major vascular surgery, delays may result in important progression of disease or death.

PERIOPERATIVE β-BLOCKADE

Mangano’s important and heavily cited²¹ trial randomized patients for major surgery including vascular surgery to be β-blocked with atenolol. He demonstrated a decrease in cardiac mortality as well as all-cause mortality. Studies that followed supported his conclusions and led to enthusiastic embrace of perioperative β-blockade.

The POISE study,²² a multicenter placebo-controlled trial of fixed metoprolol dosing for patients facing intermediate- and high-risk surgery with at least one clinical risk factor for coronary artery disease echoed Mangano’s findings vis à vis cardiac morbidity. However, the all-cause mortality for patients who received metoprolol was higher due to the increased rate of stroke. Concluded differently, the β-blockade of intermediate-risk patients may cause harm.

Without question, cessation of β-blocker therapy preoperatively leads to poorer outcome. Equally harmful is the indiscriminate β-blockade of surgical patients without strong evidence of coronary artery disease. Patients undergoing vascular surgery, particularly open surgery above the inguinal ligament, should be considered for titrated β-blockade if they have known coronary artery disease and have two or more clinical risk factors.

INTENSIVE PERIOPERATIVE MANAGEMENT

The rationale for using aggressive perioperative medical intervention to reduce cardiac risk is compelling. Many of the major cardiac risk factors such as congestive heart failure, myocardial ischemia, and dysrhythmias are detectable and amenable to therapy. Factors contributing to oxygen supply and demand balance beyond β-blockade would include appropriate treatment of hypertension, diagnosis and treatment of anemia, and appropriate treatment of pulmonary disease. Inpatient optimization and resuscitation have not led to changes in outcome. A multicenter randomized trial of the use of the pulmonary catheter–derived hemodynamic goals in almost 2000 high-risk patients undergoing elective abdominal, thoracic, vascular, and major orthopedic surgery showed no benefit over standard care.²³

PULMONARY ARTERY CATHETER

There is no indication for routine use of the pulmonary artery catheter (PAC) to aid decision making for the high-risk surgical patient. Dr Swan, in an elegantly written review in 2005 stated quite strongly: “The PAC is a diagnostic device only and has no therapeutic role.” (authors’ emphasis)²⁴ The PAC-man trial,²⁵ a large prospective cohort study of mixed medical and surgical patients in the ICU showed no improvement in outcome in those patients with pulmonary artery catheterization. Meta-analyses published in JAMA²⁶ and the Cochrane Database of Systematic Reviews²⁷ echo these findings. Even more damning, clinicians may be misinterpreting catheter-derived data at a high rate.²⁸ Worse yet, clinicians may be subjecting their patients to the risk of catheter insertion and not using all the information available.²⁹ The authors do not question the value of identifying right heart failure or pulmonary hypertension in surgical patients. Important changes to anesthesia and surgical care can be made to favor hemodynamics in that setting. Still, given the paucity of data supporting its use and given a known rate of serious complications, Swan’s catheter should be reserved for very, very few patients.

TRANSESOPHAGEAL ECHOCARDIOGRAPHY

Transesophageal echocardiography (TEE) is a sensitive marker of myocardial ischemia, often revealing segmental wall motion abnormalities before other signs of ischemia become obvious. TEE has been advocated to detect intraoperative ischemia, and has been shown to have superior sensitivity and specificity (sensitivity 75%, specificity 100%) in comparison to two-lead ECG (sensitivity 56%, specificity 98%) and pulmonary capillary wedge pressure (sensitivity 25%, specificity 93%).³⁰ A larger study (224 patients) confirms that TEE is frequently influential in guiding clinical decision making.³¹ In comparison to two-lead ECG and PAC, intraoperative TEE was the most important intraoperative guiding factor in decision making for anti-ischemic therapy, fluid administration, and vasopressor or inotrope administration. The technique itself requires expensive equipment and specialized training. Even at centers where TEE is standard of care for cardiac anesthesia, the resource is not routinely available for noncardiac surgery patients. New miniature, disposable technology may allow greater utilization.³² No guidelines have suggested Class I indications for TEE in the noncardiac surgery population.

RESOURCE ALLOCATION

If aggressive hemodynamic monitoring in the ICU is responsible for the improved survival of patients with ischemic heart disease following noncardiac surgery, the financial implications are staggering. In Rao’s study, more than 1300 ICU days of care were required to bring about a 2.4% reduction in the reinfarction rate. However, if admission criteria were restricted to congestive heart failure, angina plus congestive heart failure, or angina plus hypertension, this would account for almost 80% of the perioperative infarctions, and reduce ICU days to <300.³³ Studies have suggested that most perioperative myocardial infarctions occur within the first 2 postoperative days suggesting a shorter period of monitoring may be sufficient.³⁴

TYPE OF SURGERY: TYPE OF ANESTHETIC

As discussed previously, Eagle recognized that noncardiac operations may be divided into those that are likely to provoke perioperative ischemia and those that do not increase the risk of ischemia above normal. Major vascular procedures involving aortic cross-clamping and infrainguinal arterial bypass carry a high risk of postoperative ischemia,³⁵ as do major abdominal and thoracic procedures. Orthopedic procedures such as total hip arthroplasty have a lower incidence of cardiac morbidity, and are deemed intermediate risk. Peripheral nonvascular procedures such as transurethral resection of the prostate, an operation frequently performed in patients with coexisting coronary artery disease, are associated with a low incidence of perioperative MI.³⁶