Chapter 1

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 post-operative 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.

Appendix 1 is the perioperative screening tool for surgical patients at St. Michael’s Hospital in Toronto, Canada. Patients identified preoperatively with severe disease or gravid patients for non-obstetric 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 (Appendix 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 non-parametric scale, morbidity and mortality does 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.

Assessment of Preoperative CNS risk

Delirium is common postoperative, particularly in elderly patients who are 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 surgery and anesthesia (Appendix 3). Patients who have received regional anesthetics, thus likely exposed to less opiates, have the same rate of delirium as those who have undergone general anesthetics.⁷ Other factors common to our aging population such as structural (stroke, brain injury) and non-structural (psychiatric) brain disease increase the risk for delirium. A recognized risk of delirium allows early treatment.

Postoperative pain is an important risk factor for 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. Inadequate pain control is even more frequent in the critical care units with reliance on PL sedation without concomitant analgesia. Many ICU’s do not have a formal sedation and analgesia protocol and, patients risk being sedated without analgesia,⁸ increasing risk for postoperative delirium.

Postoperative delirium requires a multimodal treatment strategy. While haloperidol is sometimes considered, the evidence for improved outcomes is lacking. Pre-treating patients at risk for delirium has had limited success.¹⁰

Identifying risk of delirium allows preventive treatment. 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, treatment of dehydration, appropriate nutrition and avoiding polypharmacy.

Assessment of Cardiac Morbidity for Non-Cardiac Surgery

Our aging population, rising rates of obesity and Type II diabetes suggest that more patients presenting for non-cardiac surgery will have diagnosed or clinically suspected ischemic heart disease and thus increased risk for perioperative complications. Using multivariate analysis of 1,001 consecutive patients presenting for non-cardiac surgery, Goldman and associates developed an index for perioperative risk (Cardiac Risk Index; CRI) based on clinical, electrocardiographic (ECG), and routine biochemical parameters.9 The strongest predictors of cardiac morbidity were the severity of CAD, 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 exam findings. At present, the standard for perioperative cardiac risk assessment combines surgery specific risk, the Eagle criteria, (Appendix 4) and medical risk (Revised Lee CRI).⁴ The Lee index also includes surgical risks as one of the variables however only considers supra-inguinal 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%. Modern vascular surgery techniques such as endovascular aortic aneursysm repair (EVAR) compared to open surgery, demonstrate reduced perioperative risk thus calling into question Eagle’s definition.

In 2007, the American College of Cardiology and the American Heart Association published their guidelines for preoperative assessment. The guidelines were updated only two years later to reflect new perioperative beta blockade information.¹²

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 non-cardiac surgery delayed for full cardiac evaluation and treatment.

Patients in the intermediate-risk category will benefit most from the investigations, 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 cardio-respiratory disease. In addition, North America and many other Western countries are in the midst of an obesity epidemic with associated sedentary lives. The lack of symptoms in this large segment of the population results from “auto Beta blockade.” The patients never achieve, in their day-to-day activities, enough physiologic challenge to reveal their disease.

It is anticipated that in patients having high risk non-cardiac surgery, revascularization should improve outcome. Early recommendations for preoperative coronary artery bypass grafting (CABG) based on retrospective data or historical controls 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. There were no differences between groups in terms of short term or long term outcome. Other trials which addressed relative weakness of CARP reported similar results. It is difficult to dispute that if the patient has an independent reason for urgent coronary revascularization such as left main CAD or continued ischemia following myocardial infarction coronary revascularization should precede elective non-cardiac surgery. Present evidence would suggest that if important but non critical CAD is identified, preoperative revascularization will delay access to non-cardiac surgery without definite benefit. In the setting of oncologic surgery and major vascular surgery, delays may result in important progression of disease or death.

Mangano’s important and heavily cited14 trial randomized patients for major surgery including vascular surgery to be beta blocked with atenolol. He demonstrated a decrease in cardiac mortality as well as cause mortality. Studies that followed supported his conclusions and led to enthusiastic embrace of perioperative beta blockade.

The POISE study,¹⁵ a multicentre placebo control trial of fixed metoprolol dosing for patients facing intermediate and high risk surgery with at least one clinical risk factor for CAD echoed Mangano’s findings vis-à-vis cardiac morbidity. However, the cause mortality for patients who received metoprolol was higher due to the increased rate of stroke. Concluded differently, the beta blockade of intermediate risk patients may cause harm.

Since POISE, an analysis of beta blocker data with only the most secure studies included suggest that beta blockers increase perioperative mortality The authors believe that beta blocking medications should not be discontinued if already initiated by the patients caring physician. Initiation of beta blockers should only be used to treat active ischemia and not as a preventative measure.

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 beta 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 2,000 high-risk patients undergoing elective abdominal, thoracic, vascular, and major orthopedic surgery, showed no benefit over standard care.16

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” (emphasis the authors’).¹⁷ The PAC-man trial,¹⁸ 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-analysis published in JAMA and the Cochrane Database echo these findings. Even more damning, clinicians may be misinterpreting catheter derived data at a high rate. Worse yet, clinicians may be subjecting their patients to the risk of catheter insertion and not using all the information available. 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 (TEE)

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%). A larger study (224 patients) confirms that TEE is frequently influential in guiding clinical decision-making.¹⁹ 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 non-cardiac surgery patients. New miniature, disposable technology may allow greater utilization. No guidelines have suggested class 1 indications for TEE in the non-cardiac surgery population.

Major surgery is associated with an intense sympathetic and procoagulant response, which may be implicated in the development of myocardial ischemia. These neurohumoral responses to surgery may be diminished with the use of epidural anesthesia and analgesia (EAA) extending into the postoperative period. Stress-mediated release of hormones such as cortisol, antidiuretic hormone, and catecholamines is blunted by epidural anesthesia. In addition, postoperative pain may contribute to tachycardia and resultant subendocardial ischemia. Early studies showed a dramatic reduction in cardiac complications in patients treated with EAA in comparison to general anesthesia (GA) alone. This opinion was further upheld by a large systematic review of relevant trials of epidural or spinal anesthesia versus GA over the past 30 years, which showed a statistically and clinically significant reduction in mortality and morbidity after surgery. This retrospective work was prospectively tested by a large (915 patients) randomized controlled trial of high-risk surgical patients who either received EAA (intraoperatively and up to 72 hours postoperatively) with GA or GA alone with intraoperative and postoperative opioids as the mainstay of the analgesic regimen. The group observed no reduction in mortality or cardiac morbidity between groups. The only clinical benefit documented was a reduction in postoperative respiratory failure. However, the authors commented that 15 epidurals were required to prevent one episode of respiratory failure. They also commented that in no cases were there any serious complications with catheter placement or postoperative problems directly attributable to the placement of the epidural.

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