Perioperative Risk Assessment



Fig. 2.1
Cardiac evaluation and cardiac care prior to noncardiac surgery. *Noninvasive testing may be considered before surgery in specific patients with risk factors if it will change the management. †Clinical risk factors include ischemic heart disease, compensated or prior heart failure, diabetes mellitus, renal insufficiency, and cerebrovascular disease. ‡Consider perioperative beta-blockade for populations in which this has been shown to reduce cardiac morbidity/mortality. LOE level of evidence, MET metabolic equivalent (Modified from Fleisher et al. [2])



Surgical complexity is difficult to quantify. The NICE guidelines for surgical stress has four categories in order to help group procedures by the amount of physiological stress that may result (Table 2.1) [3]. Colonic resection is considered grade 4 (major +) along with total joint replacement, lung operations, neurosurgery, and cardiac surgery. This division is somewhat arbitrary, as even within each category, not all procedures are equal. When evaluating surgical stress, the surgeon must also take into account the effect of body habitus, fluid shifts, the potential for blood loss, and prolonged surgery. Re-operative surgery also adds to complexity, which in turn is affected by the surgeon’s level of expertise and experience. When there is more than one procedure available as in rectal prolapse, you may opt for a less invasive approach in a high-risk patient. Although often implied, there is no evidence that a laparoscopic approach presents a lower risk to patients, and stress level alone does not appear to have affected the uptake of laparoscopy in colorectal cancer [4].


Table 2.1
National Institute for Health and Care Excellence (NICE) classification of surgical stress























Grade 1

Minor

Excision of lesion of skin; drainage of breast abscess

Grade 2

Intermediate

Primary repair of inguinal hernia; excision of varicose vein(s) of leg; tonsillectomy; adenotonsillectomy; knee arthroscopy

Grade 3

Major

Total abdominal hysterectomy; endoscopic resection of prostate; lumbar discectomy; thyroidectomy

Grade 4

Major+

Total joint replacement; lung operations; colonic resection; radical neck dissection; neurosurgery; cardiac surgery


From: Reynolds et al. [3]

What is clear, however, is that any patient who requires emergency surgery is at a higher risk for complications regardless of the presence or absence of any other variables. This is especially true in the elderly population [5]. Unfortunately, in most cases, you will have little opportunity to modify even known risk factors in this setting. It requires tremendous coordination between you and the anesthesiologist in the perioperative setting, along with the critical care team postoperatively, to follow these patients closely, anticipate potential problems based on their risk factors, and hopefully mitigate or manage them early as they arise.



Assessing an Anesthesia-Specific Risk


Key Concept: Anesthetic risk is a combination of the effects of the anesthetic agents and, in large part, the skill level of the anesthesiologist.

Modern anesthesia is typically very safe, with an estimated risk of death from anesthesia at 1 per 200,000–300,000 anesthetics [6]. Based on the American Society of Anesthesiologists (ASA) physical status classification system, a normal healthy ASA class 1 patient has a mortality rate of less than 0.03 %. The rate increases to 0.2 % for class 2 patients, 1.2 % for class 3 patients, 8 % for class 4 patients, and 34 % for class 5 patients [7]. Significant perioperative morbidity is also related to ASA status, with a relative risk of 2.2 and 4.4 for ASA classes 3 and 4, respectively [8].

A number of meta-analyses have shown that overall mortality is lower in patients receiving neuraxial anesthesia (epidural or spinal) when compared to general inhalation anesthesia. Much of this difference is due to lower rates of thromboembolic disease, pneumonia, and respiratory depression [911]. In general, there is no difference in the rate of cardiac events between general and neuraxial anesthesia, though every effort is made to support the blood pressure during induction of general anesthesia. Patients who are being considered for neuraxial anesthesia for postoperative pain control may also gain additional benefits from the point of view of enhanced recovery, although this has not been consistent in the literature [12].

Several special devices are at the disposal of (and often used by) the anesthesiologist to enhance intraoperative monitoring. These include central venous catheters for volume status, arterial catheter for continuous blood pressure monitoring and frequent blood gas analysis, and pulmonary artery catheterization to monitor cardiac output, pulmonary artery pressure, and pulmonary vascular resistance. Perhaps surprisingly, there is no good evidence that any of these interventions decrease the incidence of perioperative complications. The routine use of pulmonary artery catheters for high-risk patients undergoing noncardiac surgery is not recommended [13, 14]. On the other hand, transesophageal echocardiography is increasingly being used in high-risk patients undergoing high-risk procedures to promote goal-directed therapy [15]. However, the indications for this technology are still evolving and oftentimes anesthesia dependent.


Assessing a Patient-Specific Risk


Key Concept: Healthy patients can be screened with a simple questionnaire that includes age, exercise tolerance, social habits, medications, and problems with previous anesthetics. In general, selective preoperative testing should be based on a focused history and physical examination.


The Healthy Patient


The goal in evaluating the healthy patient is to identify previously unrecognized conditions or factors that may increase perioperative risk. When a healthy patient is seen in the office regarding surgery, we have them fill out a short questionnaire regarding their medical history. With respect to perioperative risk, we are specifically interested in a basic screen focused on cardiac and respiratory symptoms to elucidate occult disease. These two systems are responsible for most of the significant postoperative morbidity. In addition, there is level I data for effective preventative strategies geared towards them. As such, we consider 5 factors: patient age, exercise capacity, social habits (alcohol and smoking), medication use, and problems with previous anesthetics.


Age

Much of the age-related risk is due to the increasing prevalence of comorbidities that occur with advancing age. In a large study of 1.2 million Medicare patients undergoing elective surgery, the operative mortality for patients ≥80 years was more than twice that of patients 65–69 years of age [16]. In another study of 50,000 elderly patients undergoing elective surgery, operative mortality increased from 1.3 % in patients less than 60 years of age to 11.3 % in patients 80–89 years of age [17]. With respect to pulmonary events, a large systematic review found that age was one of the most important independent predictors for complications, even after adjusting for comorbidities [18]. Despite these negative findings, improvements in anesthetic and surgical care have reduced age-related differences such that some authors state age should not be used as the sole criteria to withhold a surgical procedure [19], while others disagree [20]. Despite the disagreement, it is not uncommon to successfully perform major abdominal procedures in relatively healthy nonagenarians and even have >90-year-old patients recover well from emergency surgery [21, 22].


Exercise Tolerance

Patients with unlimited exercise tolerance are generally at low risk for perioperative cardiopulmonary complications. A general assessment of exercise tolerance has been defined as the ability to walk two blocks on level ground without symptoms or carry two bags of groceries up one flight of stairs without symptoms [23, 24]. When these simple criteria were used prospectively in a study of 600 patients undergoing major surgery, patients with poor exercise capacity suffered twice as many postoperative complications (20 % vs. 10 %) and twice as many cardiovascular complications (10 % vs. 5 %) when compared to patients with good exercise capacity [25]. In a study of 847 patients undergoing elective abdominal surgery, poor exercise capacity was a stronger predictor of mortality than the individual risk factors comprising the Revised Cardiac Risk Index (RCRI) [26]. It is an easy question to ask and get an overall feel for the patient’s tolerance.


Social Habits

The association between social habits and increased perioperative risk is well described, and generally bad habits lead to bad outcomes. In a study of US veterans, a validated questionnaire on alcohol use administered within 1 year prior to surgery was able to stratify patients for risk of surgical site infections, overall infections, and cardiopulmonary complications [27]. Another small trial of patients undergoing colorectal surgery reported a beneficial effect of alcohol cessation prior to surgery on postoperative complications. Although the optimal time for cessation of alcohol is unknown, the earlier, the better [28]. You should note, however, that stopping in a time frame where acute withdrawal is likely to occur (i.e., DTs) would not be ideal.

Smoking is strongly associated with postoperative morbidity, especially pulmonary and wound complications, and mortality [29]. Yet, there is something you can do about it, if you can get your patient to quit. A recent meta-analysis of 6 randomized trials and 15 observational studies demonstrated a significantly lower overall risk of postoperative complications with cessation of smoking [30]. In contrast to alcohol use, complication rates were inversely proportional to longer smoke-free periods; thus, preoperative counseling and adjunctive measures to stop smoking should be encouraged.


Medications

In addition to a complete list of prescription medications and allergies, a medication screen must include information on both over-the-counter and alternative medications. Aspirin and other nonsteroidal anti-inflammatory medications are commonly used and potentially effect hemostasis. Patients often forget to include them as medications, except if directly asked by name. Some alternative medicines are associated with an increased risk of perioperative complications, but because they are “natural,” patients may only provide information on direct questioning. A complete list of these medications is beyond the scope of this review. However, there are several excellent reviews of the common alternative medications and their potential perioperative effects [31].


Anesthetic Issues

Likely, the most important question you can ask in this category relates to their past history with anesthetics. Patients who have had problems with previous surgery or anesthetics should receive a preoperative anesthesia consult. This includes a family history of anesthetic problems, which may mandate additional preoperative investigations or intraoperative precautionary measures. Other anatomical factors that must be considered include the finding of a potentially difficult airway due to limitations on mouth opening, micrognathia, obesity, and limitations of neck extension in patients with cervical arthritis. Furthermore, patients who are undergoing a laparotomy require a thorough preoperative discussion of the options for postoperative pain control.

The initial preoperative screen is supplemented with a thorough physical examination. Based on any positive findings from either the history or physical examination, selective investigations are ordered, and if appropriate, a medical consult is organized.


Preoperative Testing

Key Concept: Preoperative testing should be selective and based on positive findings from a focused history and physical examination.

There is ample evidence that nonselective testing of healthy patients rarely results in a positive test that in turn is unlikely to result in a significant adverse event [3235]. Because of the low incidence of significant abnormalities in healthy patients, the positive predictive value of specific tests is also very low. You should remember that nonselective testing actually increases the rate of false-positive results, which then necessitate further testing, increased expense, inconvenience, and a possible delay of surgery. Furthermore, a normal test does not necessarily reduce the risk of an adverse perioperative event [36].

This is not to say that you should never order tests. Baseline preoperative tests may be indicated when the proposed surgery is expected to significantly alter values (i.e., large operation in a patient with baseline mild renal insufficiency—see below) or if an asymptomatic patient is in a high-risk group for a specific condition. There should be an expectation of an abnormal result that is relevant for anesthesia or surgical care.

At the present time, we check a baseline hemoglobin in healthy patients who are at risk of significant blood loss such as colonic resection or in patients with a high chance of anemia due to their underlying disease process. We do not routinely check electrolytes, blood glucose, liver function, hemostasis, or urinalysis in healthy patients undergoing either a colonic resection (moderate risk) or outpatient low-risk surgery. We do get a serum Cr in patients over 50 years of age undergoing colonic resection and in all patients suspected of having renal dysfunction (see below). We do not order a routine ECG unless patients are over 60 years of age or have other specific clinical indications such as asthma or smoking. Routine preoperative chest X-rays are not ordered in healthy patients. They may also be part of a workup for malignant disease when a chest CT has not been performed (Table 2.2).


Table 2.2
Revised Cardiac Risk Index (RCRI)




































Predictors

Number of predictions

Risk (cardiac death, nonfatal myocardial infarction, and nonfatal cardiac arrest) (%)

History of ischemic heart disease

0

0.4

History of congestive heart failure

1

1.0

History of cerebrovascular disease (stroke or transient ischemic attack)

2

2.4

History of diabetes requiring preoperative insulin use

3

5.4

Chronic kidney disease (creatinine >2 mg/dL)

>3

5.4

Undergoing suprainguinal vascular, intraperitoneal, or intrathoracic surgery
   


Modified from Lee et al. [40]


The Comorbid Patient


Key Concept: Patients with newly recognized or known comorbidities require preoperative consultation with system evaluation and the institution of preoperative strategies to minimize risk and maximize safety.


Consultation

The preoperative evaluation of specific comorbidities and anesthetic risks requires consultation. Good communication is paramount. The surgeon should provide all the essential history and physical findings, diagnostic imaging, and laboratory results. The consult should be centered on a very specific question usually regarding specific comorbidities. Asking for the patient to be cleared for surgery is not sufficient. In addition, the urgency of the surgery should be indicated; is the condition emergent, urgent, or elective? For complicated or emergent cases, we try to discuss the case directly with the internist prior to the consult. It is sometimes helpful for the internist to understand the surgical options and the potential compromises that may have to be made depending on the degree of patient-specific risk. In high-risk non-emergent situations, the patient may see the internist prior to a final decision regarding surgery, especially when the preoperative assessment is an important part of the decision to operate.

Try to direct the consult to the specialist who is best equipped to provide not only an answer but also specific treatment and postoperative support should a complication arise. If a patient has a single-system disease with a previously established relationship (i.e., cardiology or nephrology only), we use that consultant and reserve the general internist for those with multisystem disease.

In complex cases or patients at very high risk due to extensive comorbidities or high procedural risk, arrangements should be made in advance for ICU support. While open units have been the norm in the past, most hospitals are moving towards closed ICUs. A frank discussion with the patient regarding the potential for ICU admission, ventilator dependency, and the level of acceptable resuscitative measures must occur and must be communicated preoperatively to the ICU team.



Cardiovascular Risk Assessment and Risk Reduction


Key Concept: Cardiovascular risk is best assessed using one of the welldefined cardiac risk indices. Highrisk patients with significant cardiovascular disease may require preoperative stabilization with medical therapy, and in some cases, preoperative revascularization to decrease risk.

Cardiovascular risk assessment is based on an evaluation of specific predictive clinical variables, exercise capacity, and surgery-specific risk. The algorithm for cardiovascular risk assessment is reproduced in Fig. 2.1 [1]. Patients at high risk of cardiovascular events who require emergency surgery may not have time to be fully evaluated or medically optimized due to the urgency of their surgical problem. In this situation, clinical conditions should be documented for monitoring with management and stabilization occurring intraoperatively and in the postoperative period.

In the urgent or elective situation, there are several factors that increase the risk of significant postoperative cardiac events such as myocardial infarction (MI), heart failure, and death. These factors include unstable angina, severe angina or recent MI (within 30 days), decompensated heart failure, significant arrhythmias, and severe valvular heart disease. When these factors are present (especially in combination), a very careful preoperative evaluation is required and may justify a delay in, or even preclude proceeding with, surgery. In addition, there are a number of secondary clinical variables that include a history of ischemic heart disease, cerebral vascular disease, compensated heart failure or prior heart failure, diabetes mellitus, and renal insufficiency, which are also predictive for cardiovascular morbidity [37]. While many of them are incorporated into the clinical risk indexes outlined below to give an overall risk score for the patient, they do have independent associations with worse outcomes as well.

An evaluation of patient-specific risk also includes an assessment of exercise tolerance. As noted previously, poor exercise tolerance has been defined as the inability to walk two to four blocks or climb two flights of stairs at a normal pace due to the development of dyspnea, angina, or excessive fatigue. This translates to a metabolic equivalent of ~4 (4 MET), and failure to achieve this is predictive of in-hospital perioperative risk. Additional activities with a similar metabolic equivalent include carrying objects of 15–20 lb and playing golf or doubles tennis.

The overall perioperative cardiovascular risk for each individual patient is determined using one of several cardiac risk indexes. In 1977, Goldman was one of the first to develop a cardiac risk index using nine variables to predict the development of cardiac complications [38]. Since then, several others have come along—some cardiac-specific, and others more general (i.e., ASA Classification [39, 70]; Table 2.3). Earlier, we introduced the Revised Cardiac Risk Index (RCRI) or Lee Index, as it is one of the most widely used due to its simplicity and clinical utility [40] (Table 2.2). It is the primary index applied at our center and is based on the presence or absence of six predictive factors: highrisk surgery, ischemic heart disease, congestive heart failure, cerebrovascular disease, diabetes mellitus, and renal dysfunction. Patients receive one point for each risk factor that is present to give a cumulative index score. The rate of development of a major cardiac event—defined as myocardial infarction, pulmonary edema, ventricular fibrillation/cardiac arrest, and complete heart block—is estimated to be 0.4 % (95 % CI 0.1–0.8 %), 1 % (95 % CI 0.5–1.4 %), 2.4 % (95 % CI 1.3–3.5 %), and 5.4 % (95 % CI 2.8–7.9 %) for scores of 0, 1, 2, and ≥3, respectively [41, 42]. Using the AHA algorithm, patients at high risk for cardiac complications (score ≥3) should undergo noninvasive cardiac (stress) testing. If severe myocardial ischemia is identified, coronary revascularization should be considered prior to planned surgery (if possible), in addition to preventative medical strategies outlined below.


Table 2.3
American Society of Anesthesiologists (ASA) classification
























ASA1

A normal healthy patient

ASA 2

A patient with mild systemic disease

ASA 3

A patient with severe systemic disease

ASA 4

A patient with severe systemic disease that is a constant threat to life

ASA 5

A moribund patient who is not expected to survive without the operation

ASA 6

A declared brain-dead patient whose organs are being removed for donor purposes


Modified from the American Society of Anesthesiologists (ASA) [70]

There are modifications—the addition of “E” for an emergency and the addition of “P” for pregnancy

Recently, a new predictive risk model for perioperative myocardial infarction/cardiac arrest was constructed from the American College of Surgeons National Surgery Quality Improvement Program (NSQIP) database [43]. This model is based on a very large patient cohort where more recent preventive and interventional cardiac strategies were applied. On multivariate regression analysis, significant predictive variables included type of surgery, dependent functional class, abnormal creatinine, ASA class, and increased age. This model is not as well known; thus, many internists are not comfortable using it. However, when compared directly to the RCRI model, it demonstrated higher predictive accuracy. An online calculator has been created which makes it easy to apply by the surgeon to determine individual risk [44].

Perioperative medical therapy for cardiac risk reduction includes B-blockers, statins, and aspirin. High-risk patients or those who take these medications preoperatively require medical consultation. Based on recent evidence, preoperative B-blocker use has been limited to specific risk groups and must be introduced gradually. Despite good evidence for the beneficial effect of B-blockers and statins [45, 46], the evidence for the perioperative use of aspirin and/or thienopyridine for the reduction of cardiac risk is less clear due to an increased risk of perioperative bleeding. While aspirin alone is safe, the combination of aspirin with thienopyridine is associated with an increased risk of perioperative bleeding and transfusion. To reduce the risk of bleeding, thienopyridine should be discontinued 5–7 days prior to surgery and restarted as soon as the risk of postoperative bleeding has decreased.

High-risk patients with severe cardiac ischemia may be candidates for preoperative coronary revascularization. Patients with left main stem or three-vessel CAD associated with poor left ventricular function have a recognized survival advantage with either coronary artery bypass (CABG) or percutaneous coronary intervention (PCI) including balloon angioplasty and/or stent placement. The benefits and risks of revascularization must be factored into the decision-making process. CABG has a higher procedural risk than PCI. However, PCI with stent placement is associated with an increased risk of perioperative bleeding due to the use of dual antiplatelet agents, which, if stopped prematurely, may result in stent occlusion. Ideally, colorectal surgery should be delayed ~30–45 days after placement of a bare metal stent and 1 year following a drug-eluding stent. This may not be practical in a patient with a near obstructing cancer or in the situation of a narrow therapeutic window following chemoradiation. Patients who require surgery within a month of coronary revascularization should undergo either an angioplasty without stent placement or, in select circumstances, a CABG. The colorectal surgeon must be involved in these complex decisions, especially when determining the urgency of the situation.

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Mar 23, 2017 | Posted by in GASTROENTEROLOGY | Comments Off on Perioperative Risk Assessment
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