CHAPTER 22

 

 

 

PREOPERATIVE ASSESSMENT

Paul Lee, M.D. and Miriam Rabkin, M.D., M.P.H.

 

 

The goal of medical preoperative evaluation is to assess medical problems in surgical patients, to determine how best to manage these problems during surgery, and to provide recommendations for post-operative care. On occasion, the surgeon requesting the consultation will have a specific question. More often, the internist is asked to provide "routine medical clearance." Preoperative risk assessment is a critical part of this process. This chapter will briefly discuss general principles of preoperative evaluation, and readers are encouraged to pursue the references listed at the end of the chapter for more details.

Preoperative risk assessment starts by identifying the type of surgery to be performed and the "type" of patient who is to have it. It is these two factors which determine the risk of complications - even a patient with severe coronary artery disease is at relatively low risk from cataract surgery, and even a patient without coronary artery disease is at relatively high risk from a pneumonectomy. If the medical consultant is confident in the assessment of the risk from surgery and the risk conferred by the patientís health, there is no need for further testing. (The absence of cardiac stress testing is not equivalent to the absence of data!) It is patients who are judged to be at "intermediate" risk, or those whose risk is unknown who should be referred for further evaluation.

The first part of this equation, the risk to patients from specific types of surgery, has been studied extensively. As a rule, operative death is uncommon, occurring in about 0.3 percent of all operations. "Average risk" implies a perioperative mortality of one percent or less, "significant risk" implies one to ten percent and "high risk" ten to twenty percent. While generalizations about risk are frequently made from clinical series, it is clearly important to examine the types of patients selected for study. For example, in series of consecutive unselected patients, mortality from a particular type of operation is considerably lower than in series of patients with known coronary artery disease, or in those undergoing surgery for conditions associated with coronary artery disease - such as peripheral vascular disease. In general, procedures associated with higher mortality and complication rates include major vascular surgery (femoral-popliteal bypass, aortic aneurysm repair), cardiac surgery, intraperitoneal surgery, intrathoracic surgery and craniotomy. Emergency surgery of any type carries a higher risk of mortality and postoperative complications (Table 1).

TABLE 1: Surgery-specific risk

High risk: cardiac risk often > 5%

Aortic repair (aneurysmal, dissection)

Noncarotid major vascular (infrainguinal and intraabdominal)

Peripheral vascular surgery

Anticipated prolonged surgical procedures with large fluid shifts and/or blood loss

Major emergency procedures, particularly in the elderly

Intermediate risk: cardiac risk generally < 5%

Major intraabdominal (nonvascular)

Intrathoracic (nonendoscopic)

Major orthopedic

Carotid endarterectomy

Major head and neck

Radical prostatectomy

Low risk: cardiac risk generally < 1%

Opthalmologic (excluding prolonged retinal)

Minor head and neck

Minor prostate (such as cystoscopy or TURP)

Biopsies and superficial procedures

 

The second part of the risk equation is determined by the patientís health. The American Society of Anesthesiologists (ASA) classification gives a global impression of the clinical state of the patient that correlates well with surgical outcome. In addition to overall health, specific characteristics have been identified which may predispose patients to poor surgical outcomes; these have been codified in the risk indices discussed below.

 

Cardiac Complications of Noncardiac Surgery

Cardiac risk is the most-feared and most-studied complication of surgery and a call for "medical clearance" is often an implicit request to determine the perioperative risk of cardiac complications. As no patient and no procedure is risk-free, the medical consultant should avoid the phrases "medically cleared" or "cleared for surgery." In fact, one to five percent of patients undergoing noncardiac surgery have cardiac complications. The role of the internist is to determine patient-specific and surgery-specific risk factors, to identify if the patient is at low, average or high-risk for the procedure, and to determine if further testing is indicated.

 

EVALUATION OF CARDIAC RISK:

The evaluation of cardiac risk will always include a directed history and physical, and will almost always include a resting electrocardiogram. These data help to guide decisions regarding the need for additional testing. In "low risk" patients Ė those with no known coronary artery disease, good functional status, and low scores on the cardiac risk indices described below Ė further testing will add little to preoperative assessment. Cardiac stress testing is most useful when the patientís history is unclear, functional status is poor, or when there is a history of new or unstable chest pain. We recommend the following systematic and evidence-based approach.

  1. History:

In addition to a routine medical history, the American College of Cardiology guidelines emphasize that the following elements be included in a preoperative assessment:

  1. Physical Examination:

As always, the physical examination should be tailored to the specifics of a patientís medical history and presenting complaint (if any). The goal of the preoperative physical examination, however, is to identify conditions that increase operative risk, such as heart failure, valvular disease, and peripheral vascular disease. The ACC guidelines identify the following components of the physical examination:

TABLE 2: Functional Capacity (adapted from reference 5)

Energy Levels

Activity

1 MET

Can you take care of yourself?

Eat, dress, and use the toilet?

 

Walk indoors around the house?

 

Walk a block or two on level ground at 2 to 3 mph?

 

Do light work around the house like dusting or washing dishes?

4 METS

Climb a flight of stairs or walk up a hill?

Walk on level ground at 4 mph?

 

Run a short distance?

 

Do heavy work around the house like scrubbing floors or lifting or moving heavy furniture?

 

Participate in moderate recreational activities like golf, bowling, dancing, doubles tennis, or throwing a baseball or football?

> 10 METS

Participate in strenuous sports like swimming, singles tennis, football, basketball or skiing?

 

  1. Electrocardiogram:
  2. Although attempts have been made to codify their routine use, ECGs are frequently a part of the preoperative evaluation. Further work-up is usually not required for such abnormalities as conduction disturbances (e.g. bundle-branch block or first-degree atrioventricular block). In patients with documented coronary disease, the ECG may provide prognostic information about long-term morbidity. For example, the presence of pathologic Q waves is included as a major risk factor in all the major cardiac risk indices. In patients undergoing low-risk surgery, ECG findings do not reliably predict perioperative risk. However, in clinically intermediate- and high-risk patients, certain abnormalities (e.g. LVH or ST-depression) can predict adverse perioperative cardiac events.

  3. Cardiac Risk Indices:
  4. Several well-known indices of cardiac risk are routinely used when assessing the preoperative patient. The original Goldman risk index, published in 1977, was based on a series of 1001 unselected patients over the age of 40 undergoing major noncardiac surgery. In multivariate analysis, nine preoperative factors were found to be associated with life-threatening cardiac complications and perioperative cardiac death: MI within 6 months, S3 gallop or jugular venous distension, age over 70, rhythm other than sinus on preoperative ECG, more than 5 PVCs/minute, important aortic stenosis, poor general medical status, emergency surgery and intraperitoneal, intrathoracic or aortic surgery. A point score system weighted the factors and allowed physicians to divide patients into four risk groups. Group 1, having 0 to 5 points, would have an estimated 0.7 percent of complications and 0.2 percent of death. Group 4, with 26 or more points, had estimated risks of 22 percent and 56 percent. The index was validated in large prospective series of general surgery patients, but it is important to recognize that there were relatively few patients undergoing vascular surgery in the Goldman cohort. Similarly, the data were based on patient experience from the 1970s, and do not reflect current practices in anesthesia, medicine or surgery.

    TABLE 3: Cardiac Risk Indices of Goldman and Detsky

    Risk factor

    Definition (Goldman)

    points

    Definition (Detsky)

    points

    CAD

    MI within 6 months

    10

    MI within 6 months

    10

         

    MI > 6 months ago

    5

         

    class III angina

    10

         

    class IV angina

    20

         

    unstable angina within 6 months

    10

    CHF

    S3 gallop or JVD

    11

    pulmonary edema

    within 1 week

    ever

    10

    5

    Rhythm

    rhythm other than sinus or PACs on last ECG prior to surgery

    7

    rhythm other than sinus or sinus + PACs on last ECG

    5

     

    > 5 PVCs/minute at any time before surgery

    7

    > 5 PVCs/minute at any time

    5

    Valvular disease

    important aortic stenosis

    3

    suspected critical aortic stenosis

    20

    General medical status

    pO2 < 60 or PCO2 >50 or K+ < 3.0 or HCO3 < 20 or BUN > 50 or Cr > 3.0 or signs of chronic liver disease or bedridden from noncardiac causes

    3

    same as Goldman

    5

    Age

    > 70

    5

    > 70

    5

    Surgery type

    intraperitoneal, intrathoracic or aortic

    3

    emergency surgery

    10

     

    emergency surgery

    4

       
             

    Goldman index: Class I < 35, Class II = 6-12, Class III = 13-25, Class IV >25 points.

    Detsky index: Class I < 15, Class II = 20-30, Class III > 30 points

    Detksy and Larsen conducted prospective studies in the 1980s that confirmed and refined the original Goldman index, adding categories of angina and prior history of congestive heart failure. Critics of these indices note that the Detsky modified risk index may underestimate cardiac risk in vascular patients and that it does not allow precise predications for patients within the lowest risk category.

    In contrast to the relatively small numbers of vascular patients studied by the Goldman and Detsky groups, Eagle et al. studied 254 consecutive vascular surgery patients awaiting dipyridamole-thallium imaging. Although the study was retrospective, the analysis identified five clinical predictors and two thallium test predictors of postoperative cardiac events: age over 70 years, Q waves on ECG, history of angina, history of ventricular ectopy requiring treatment, diabetes mellitus requiring therapy other than diet, thallium redistribution and ischemic ECG changes during or after dipyridamole infusion. Clinical predictors alone were able to identify patients at low or high risk. Patients with none of these clinical predictors had a 3.1 percent risk of ischemic pulmonary edema, unstable angina, myocardial infarction or cardiac death, while patients with three or more clinical predictors had a 50 percent risk of this combined endpoint. Thallium testing was particularly useful in patients with one or two clinical predictors, in whom those without redistribution had a 3.2 percent risk and those with redistribution had a 29.6 percent risk. The Eagle criteria have been validated in a prospective study of patients undergoing abdominal aortic surgery.

    More recently, Lee et al. derived and validated a much simpler index for patients undergoing non-urgent major noncardiac surgery known as the Revised Cardiac Risk Index. Their analysis identified six independent risk factors: ischemic heart disease, congestive heart failure, cerebral vascular disease, high-risk surgery, preoperative insulin treatment for diabetes mellitus, and preoperative creatinine greater than 2 mg/dl (Table 4). Rather than weighting each of these risk factors, they designated risk classes by the number of risk factors. Patients without any risk factors are assigned to the lowest risk class (I) and were found to have cardiac complication rates of 0.5 percent and 0.4 percent in the derivation and validation cohorts. In contrast, patients with three or more risk factors are assigned to the highest risk class (IV) and were found to cardiac complication rates of 9.1 percent and 11 percent. When applied to their derivation and validation cohorts, this newer index outperformed the original Goldman and the modified Detsky indices.

    TABLE 4: Lee Revised Cardiac Risk Index (adapted from reference 15).

    Risk Factors

    Adjusted Odds Ratio (derivation cohort)

    High risk surgery

    2.8

    Ischemic heart disease

    2.4

    History of CHF

    1.9

    History of cerebrovascular disease

    3.2

    Insulin therapy for diabetes

    3.0

    Preoperative serum creatinine > 2.0 mg/dl

    3.0

    Risk Class

    # of Risk Factors

    Cardiac Complication Rates (%)

    Derivation

    Validation

    I

    0

    0.5

    0.4

    II

    1

    1.3

    0.9

    III

    2

    3.6

    6.6

    IV

    3-6

    9.1

    11.0

  5. Noninvasive Cardiac Testing:

There is no absolute consensus about the extent of preoperative testing that is appropriate when assessing cardiac risk, but certain general principles are evident. If a test is unlikely to effect posttest probability of poor outcome, it is an unnecessary component of preoperative risk assessment. Thus, for minimally risky procedures or minimally risky patients, further investigation is unlikely to be helpful.

While low-risk patients can proceed to surgery, and while high-risk patients may need to reconsider their surgical options (see Appendix A), it is more difficult to advise patients in the intermediate-risk category. These are the patients who are most likely to benefit from further testing. Both the American College of Cardiology (ACC)4 and the American College of Physicians (ACP) have developed guidelines regarding which patients should be referred for noninvasive cardiac evaluation (Figure1 and Figure 2).

Although some authors argue that all patients with known coronary artery disease should be evaluated with echocardiography and cardiac stress testing prior to surgery, there are no outcomes data to support this approach. Patients with stable coronary artery disease - including those who have had previous coronary artery bypass surgery - are not at increased risk, and further testing in the absence of symptoms is usually unnecessary in active patients. As noted, studies have shown that exercise tolerance is as good as exercise stress testing in predicting perioperative complications in patients with stable coronary artery disease. There may be subsets of patients with coronary artery disease, however, who will benefit from further preoperative testing. Patients undergoing vascular surgery are of particular concern because of the risks of these procedures and because the presence of peripheral vascular disease is often associated with clinically significant coronary artery disease. This population has been extensively studied and multiple series have shown that dipyridamole thallium scintigraphy has a high negative predictive value - i.e. that life-threatening cardiac complications are extremely rare in the presence of a normal thallium scan - although these trials are limited by the selected nature of their subjects.

The ACC guidelines are based on "clinical predictors" (Table 5), functional capacity (and surgery-specific risk. A patient with a major clinical predictor requires intensive management, and non-emergent surgery should be deferred. Patients with intermediate clinical predictors and either poor functional capacity (less than 4 METS, see Table 2) or high surgery-specific risk (Table 1) should undergo further risk-stratification via noninvasive stress testing. The ACP algorithm utilizes the Detsky modified cardiac risk index (Table 3) with the addition of the Eagle13 and Vanzetto criteria (Table 6).

An exercise ECG stress test is the standard method of detecting myocardial ischemia and of providing an estimate of functional capacity in most ambulatory patients. However, patients with resting ECG abnormalities may require myocardial perfusion imaging testing. For those unable to exercise to target heart rates due to claudication, arthritis, deconditioning, or pulmonary disease, pharmacological stress testing may be necessary. Dipyridamole myocardial perfusion imaging testing and dobutamine stress echocardiography have been most extensively studied, and in many instances, either test is appropriate. Choosing between these two tests often hinges upon the expertise of the local institution.

 

 

 

 

TABLE 5: ACC Clinical Predictors of Cardiac Risk

Major Clinical Predictors

Unstable coronary syndromes

  • MI within one month with evidence of important ischemic risk by clinical symptoms or noninvasive study
  • Unstable or severe angina (Canadian Class III or IV)

Decompensated heart failure

Significant arrhythmias

  • High-grade atrioventricular block
  • Symptomatic ventricular arrhythmias in the presence of underlying heart disease
  • Supraventricular arrhythmias with uncontrolled ventricular rate

Severe valvular disease

Intermediate Clinical Predictors

Mild angina pectoris (Canadian Class I or II)

Previous MI (by history or pathological Q waves on ECG)

Compensated or prior heart failure

Diabetes mellitus (particularly insulin-dependent)

Renal insufficiency

Minor Clinical Predictors

Advanced age

Abnormal ECG (LBBB, LVH, ST-T wave abnormalities)

Rhythm other than sinus

Low functional capacity (e.g. inability to climb one flight of stairs with a bag of groceries)

History of stroke

Uncontrolled systemic hypertension

 

 

 

TABLE 6: Low-risk variables of Eagle and Vanzetto

Criteria of Eagle et. al.

Criteria of Vanzetto et al.

Age > 70 years

Age > 70 years

History of angina

History of angina

Diabetes mellitus

Diabetes mellitus

Q waves on electrocardiogram

Q waves on electrocardiogram

History of ventricular ectopy

History of myocardial infarction

 

ST-segment ischemic abnormalities on resting ECG

 

Hypertension with severe LVH

 

History of congestive heart failure

 

Figure 1: ACC approach to the assessment of persons with intermediate clinical predictors


Clinical predictors:

Functional capacity:

Surgical risk:


Noninvasive testing:

Invasive testing:


 

Figure 2: ACP algorithm for low or intermediate risk patients

Adult facing surgery



Very young, very minor surgery,

no systemic disease?



Class I?






MANAGEMENT OF CARDIAC RISK:

If preoperative evaluation suggests that a patient is at high risk for cardiac complications from surgery, options include canceling the procedure or deferring it while medical or surgical therapy of the patientís coronary artery disease is implemented. While there are no randomized trials of prophylactic revascularization, coronary angiography is often appropriate in this situation, as indicated in the ACP algorithms for management of patients at high risk (Appendix A).

  1. Coronary angiography and revascularization:
  2. There have been no prospective trials of prophylactic coronary artery bypass grafting (CABG) prior to noncardiac surgery, and the benefits of this strategy are unknown. Evidence from restrospective studies suggests that the reduction in risk from revascularization is approximately equal to the risk from the surgery itself, although some trials suggest that patients undergoing high-risk noncardiac surgery may benefit from CABG if they already have well-established indications for the surgery. Therefore, the decision to refer a patient for coronary revascularization in the perioperative setting is identical to that in the non-operative setting. It is not appropriate to postpone surgery for coronary revascularization that would not otherwise have been indicated.

    Data to support prophylactic percutaneous transluminal coronary angioplasty (PTCA) are also lacking. There is some suggestion, however, that patients undergoing noncardiac surgery soon after PTCA are at higher risk for cardiac complications, and elective surgery should generally be delayed for at least two weeks after PTCA.

  3. Medical management: Beta blockade

Perioperative beta-blockade has become the mainstay of medical therapy for noncardiac surgical patients since the publication of a prospective, randomized, double-blind, placebo-controlled trial by Magnano et al. in 1996. Two hundred patients with known or suspected coronary artery disease undergoing noncardiac surgery were randomized to atenolol or placebo for the duration of their hospital stay. Overall mortality from deaths due to cardiac causes was significantly lower in the treatment group at six months (0 vs. 8%), twelve months (3 vs. 14%) and twenty-four months (10 vs. 21%), as were combined cardiovascular outcomes. Event-free survival was significantly higher in the atenolol group.

In the DECREASE trial, Polderman et al. subsequently randomized 112 high-risk patients undergoing vascular surgery to bisoprolol vs. standard care; the risk of death from cardiac causes or nonfatal myocardial infarction was dramatically reduced by beta-blockade (from 34 percent in the control group to 3.4 percent in the bisoprolol group). The effect was still significant after two years of follow-up.

An observational study of vascular surgery patients by Boersma et al. demonstrated a relative risk of 0.3 for patients on beta-blockers across all strata of the Revised Cardiac Risk Index. However, there was only a small absolute risk reduction in patients in the lowest risk class (those with no risk factors). In contrast, patients with three or more risk factors continued to be at high risk even on beta-blockers if there were five or more new wall motion abnormalities on dobutamine stress echo. The study highlights the continued importance of risk stratification in the era of perioperative beta-blockers. In some high-risk patients, beta-blockers may not sufficiently lower risk and revascularization or cancellation of the procedure may have to be considered.

Although the optimal dosing schedule for beta-blockers is unknown, it is likely that the medication should be started before hospitalization or immediately upon hospitalization. One advantage of starting beta-blockers up to a month in advance is the ability to titrate the medication to the target heart rate (65 beats/minute) prior to surgery. Perioperative beta-blockers should be continued through the hospitalization and up to a month postoperatively.

Pulmonary Complications of Noncardiac Surgery

Pulmonary function is altered in patients undergoing surgery. Decreased functional residual capacity, vital capacity and cough contribute to aspiration, atelectasis and pneumonia, frequent causes of operative morbidity. Although the reported frequency of pulmonary complications after noncardiac surgery varies widely, in part because of erratic definitions in the earlier literature, they are thought to be as common as postoperative cardiac complications. More recently, the definition of a "pulmonary complication" has been restricted to those that are clinically significant, including pneumonia, respiratory failure with prolonged mechanical ventilation, bronchospasm, atelectasis, and exacerbation of underlying chronic lung disease.

Pulmonary risk assessment:

In marked contrast to the literature on preoperative cardiovascular evaluation, there are relatively few prospective studies of preoperative pulmonary evaluation. Preoperative assessment of patients undergoing pulmonary resection is generally extensive, but studies of this population are not generalizable to other types of surgery. In general, authors agree that in patients with no history or symptoms of clinically significant lung disease and a normal lung exam, no further studies are required. Functional status correlates with pulmonary function, and in active patients a history and physical exam are usually sufficient to estimate operative risk. Routine preoperative pulmonary function testing is not recommended, and a study of routine preoperative chest X-rays in adult patients admitted for vascular surgery found that they were of no help in improving patient outcomes.

Procedure-specific risk factors:

Procedure-specific risk factors for pulmonary complications include the surgical site, the duration of surgery, the type of anesthesia, and the type of neuromuscular blockade. The surgical site is the most important risk factor. The complication rate is higher for surgical sites closer to the diaphragm such as thoracic and upper abdominal surgery. Lung resection is, unsurprisingly, associated with pulmonary complications. Prolonged surgical procedures are associated with higher risk. Although controversial, a systematic review of 141 trials including 9559 patients, reported a reduction in risk when using epidural or spinal anesthesia compared to general anesthesia. In a randomized trial comparing pancuronium, atracurium, and vecuronium, a higher incidence of postoperative pulmonary complications was found with the longer-acting neuromuscular blocker, pancuronium, than with the other agents.

Patient-specific risk factors:

Smoking increases the risk of pulmonary complications even in the absence of chronic lung disease, and all patients undergoing elective surgery should be counseled that quitting can reduce perioperative risk (see Chapter 3). Of note, the risk declines only if smoking is stopped for at least eight weeks before surgery; one study actually found a higher risk among patients who stopped smoking for less than eight weeks than in those who never stopped.

COPD increases the risk of pulmonary complications with the relative risk ranging from 2.7 to 4.7.22 In spite of the increased risk of pulmonary complications, there is no definite pulmonary function testing result that can be used as an absolute contraindication to surgery. Older studies suggested that asthma increases pulmonary complication rates, but have not been confirmed by more recent evidence. In fact, current guidelines from the National Heart, Lung, and Blood Institute state that a patient with well-controlled asthma, defined by the absence of wheezing and at > 80 percent of predicted or personal best peak flow, can safely proceed to surgery at average risk.

For patients with known asthma or chronic obstructive pulmonary disease (COPD), the goal is to maximize respiratory function; to adjust medical regimens to bring patients to their "personal best." While an FEV1 of less than 500 cc or an FVC of less than one liter are generally considered prohibitively dangerous findings, severity of disease or of PFT abnormalities do not strictly correlate to risk of postoperative complications. Patients with uncharacterized lung disease may benefit from preoperative PFTs and a specific diagnosis, particularly before thoracic or upper abdominal surgery, although type and duration of surgery and the patientís functional status remain the most important predictors of operative outcome.

Poor general medical status is a risk factor for pulmonary complications. In fact, the Goldman risk index predicts pulmonary as well as cardiac complications. However, poor exercise capacity is likely the strongest predictor of pulmonary complications. Obesity and age have not been shown to be independent risk factors for pulmonary complication in most studies. A recent report suggests that some metabolic markers (albumin < 3 gm/d and BUN > 30 mg/d) are predictors of pulmonary complications.

Pulmonary risk indices:

There are several pulmonary risk indices, none of which has been broadly validated. Epstein proposed the Cardiopulmonary Risk Index (CPRI) in 1993. Developed for use in patients undergoing lung resection, the CPRI is based on the Goldman criteria, with added pulmonary-specific risk factors of obesity, smoking, cough, diffuse wheezing, FEV1/FVC < 70 percent and hypercapnia. The Brooks-Brunn risk index is based on six risk factors found to be independently associated with increased pulmonary risk after abdominal surgery. It includes age greater than 60 years, obesity, impaired cognitive function, a history of cancer, smoking and the presence of an upper abdominal incision. The Lawrence risk index is based on a retrospective review of 2291 patients undergoing abdominal surgery. It uses the risk factors of an abnormal lung exam, abnormal chest X-ray, the Goldman risk index, and the Charlston Comorbidity index. The Multifactorial risk index, the most recent entry, is based on a large prospective cohort study on VA patients that included both derivation (n = 81,719) and validation (n = 99,390) cohorts. It is interesting to note that the procedure-specific risk factors are weighted higher than patient-specific risk factors. Of the four available indices, the Lawrence and Multifactorial indices are the most appealing since they were derived from large numbers of abdominal surgery patients and since PFTs are not required.

TABLE 7: Pulmonary risk reduction

Preoperative:

  • encourage smoking cessation for at least eight weeks
  • treat airflow obstruction in patients with COPD or asthma
  • administer antibiotics and delay surgery if respiratory infection is present
  • begin patient education regarding post-operative lung-expansion maneuvers

Intraoperative:

  • limit duration of surgery to less than three hours
  • use spinal or epidural analgesia*
  • avoid use of pancuronium
  • use laparascopic procedures when possible

Postoperative:

  • use deep-breathing exercises or incentive spirometry
  • use continuous positive airway pressure (CPAP)
  • use epidural analgesia*
  • use intercostal nerve blocks*

* often recommended but variable efficacy in literature

Pulmonary risk reduction strategies:

Perioperative interventions have been shown to reduce the incidence of pulmonary complications. Patients who stop smoking two months prior to surgery have significantly fewer pulmonary complications than those who continue to smoke or stop less than eight weeks before admission. Incentive spirometry and chest physiotherapy have been shown to reduce pulmonary morbidity. Adequate analegesia and early mobilization are strongly recommended. Table 7 is adapted from Smetanaís review of preoperative pulmonary evaluation32 and summarizes risk reduction strategies. While small studies suggest that the use of doxapram, a respiratory stimulant, might reduce pulmonary complications, these data are preliminary and do not yet warrant routine use of this agent.

Hematologic Risk

Although severe anemia and thrombocytopenia are associated with perioperative complications, the chance of these abnormalities being discovered in a healthy patient with no history of disease is extremely small. Mild anemia does not predict poor operative outcome and while it is traditional to recommend that patients be transfused for hematocrit less than 30 percent, this may be unnecessary for patients with chronic anemia. Hematocrit less than 24 percent was associated with increased morbidity in a 1988 study. Similarly, while severe thrombocytopenia (less than 50,000) is associated with increased bleeding complications screening asymptomatic patients for platelet abnormalities is unlikely to be productive and routine preoperative coagulation profiles are not recommended. A history of bleeding diathesis, cirrhosis, hematologic malignancy or easy bruisablility should prompt assessment of platelet count and prothrombin time.

Patients on antiplatelet medications (such as aspirin) or who are chronically anticoagulated fall into two categories. Those needing "tight control" - i.e. those with mechanical heart valves - can be placed on heparin preoperatively. Those in whom "loose control" is acceptable - patients on aspirin for CAD or warfarin for CVA prophylaxis - can discontinue anticoagulation a week prior to surgery and resume the medications on postoperative day one. NSAIDS should also be discontinued five to seven days before surgery.

Prophylaxis of deep venous thrombosis is particularly important after surgery. Patients undergoing pelvic or lower extremity surgery are at highest risk, particularly those having hip or knee replacement. For healthy patients under the age of 40 undergoing general surgery, early ambulation is sufficient. For older patients, elastic stockings and low-dose heparin (5,000 units SQ bid) are recommended. Orthopedic patients with hip fractures or undergoing hip replacement are prophylaxed with warfarin or low-molecular-weight heparin.

Chronic Medications

It is important to consider every medication a patient is taking, and its implications for the perioperative period. Diabetics will require adjustment of insulin or oral hypoglycemics; type one diabetics should be followed by the inpatient medical consult team. Patients on chronic steroids will require stress-dose steroids. Patients on antihypertensive medications may require parenteral equivalents while NPO. Anti-ischemic regimens can be changed to transdermal or parenteral equivalents. A careful review with the patient should also include alcohol use and evaluation of the potential for alcohol withdrawal while hospitalized.

 

 

Risk Assessment

Good communication is an essential feature of preoperative evaluation. Findings and recommendations should always be discussed with the referring surgeon, ideally in person. Notes should be brief, focused and specific. The goal of preoperative risk assessment is to determine if a patient is at average or increased risk for a specific procedure, or to recommend diagnostic testing if this determination cannot yet be made. As no patient is clear of risk, the phrase "medical clearance" is misleading and should not be used by a medical consultant. The patient should understand that medical consultation has been requested by their surgeon, that the two services are working together as a team to optimize their care and that the final decision on whether or not to operate will be made by the surgeon.

 

 

Appendix A: ACP algorithm for the management of patients at high risk


 

 

 

 

 

 

 


Yes No