1 What are the goals of the preoperative evaluation?

The preoperative evaluation consists of gathering information about the patient and formulating an anesthetic plan. The overall objective is reduction of perioperative morbidity and mortality. Ideally the preoperative evaluation is performed by the person who will administer the anesthetic.

2 Discuss the important features of the preoperative evaluation

The anesthesiologist should review the surgical diagnosis, organ systems involved, and planned procedure. Important features include personal interview, physical examination, and review of medical records. Important questions involve medications, drug allergies, substance abuse (e.g., cigarettes, alcohol, illicit drugs), review of systems, and prior anesthetic experience (i.e., history of difficult intubation, delayed emergence, malignant hyperthermia, prolonged neuromuscular blockade, or postoperative nausea and vomiting). From this evaluation the anesthesiologist decides if any preoperative tests or consultations are indicated and then formulates an anesthetic care plan.

3 How often does the preoperative evaluation alter care plans?

It has been found that care plans were altered in 20% of all patients (including 15% of American Society of Anesthesiologists [ASA] class 1 and 2 patients) because of conditions identified at the preoperative evaluation. The most common conditions resulting in changes were gastric reflux, insulin-dependent diabetes mellitus, asthma, and suspected difficult airway. These findings indicate that, whenever possible, it is preferable in all patients to do the preoperative evaluation before the day of surgery.

4 What are the features of informed consent?

Informed consent involves the communication of the anesthetic plan in terms the patient understands and covers everything from premedication and preoperative procedures to intraoperative management and postprocedural care (e.g., management of pain, nausea, and vomiting). The alternatives, potential complications, and risks vs. benefits are discussed, and the patient’s questions are answered. Preoperative evaluation and informed consent establish a trusting doctor-patient relationship that significantly diminishes patient anxiety and measurably influences postoperative recovery and outcome.

5 What is the physical status classification of the ASA?

The ASA classification was created in 1940 for the purposes of statistical studies and hospital records. It is useful both for outcome comparisons and as a convenient means of communicating the physical status of a patient. Unfortunately it is imprecise, and a patient often may be placed in different classes by different anesthesiologists. In addition, the higher ASA class only roughly predicts anesthetic risk. The six classes are:

Class 1: A normal healthy patient.

Class 2: A patient with mild systemic disease.

Class 3: A patient with severe systemic disease.

Class 4: A patient with severe systemic disease that is a constant threat to life.

Class 5: A moribund patient who is not expected to survive without the operation.

Class 6: A declared brain-dead patient whose organs are being removed for donor purposes.

An “E” is added to the status number to designate an emergency operation.

6 How long should a patient fast before surgery?

In 1999 the American Society of Anesthesiologists task force on preoperative fasting reviewed a series of studies and compiled guidelines for practitioners (Table 17-1).

TABLE 17-1 Preoperative Fasting Recommendations

These guidelines should be modified according to the patient’s disease state and airway difficulty. Current fasting guidelines for pediatric patients are as follows: clear liquids up to 2 hours before surgery; breast milk up to 4 hours before surgery; and solid foods, including nonhuman milk and formula, up to 6 hours before surgery.

7 What are the appropriate preoperative laboratory tests? Which patients should have an electrocardiogram? Chest radiography?

No evidence supports the use of routine laboratory testing. Rather, there is support for the use of selected laboratory analysis based on the patient’s preoperative history, physical examination, and proposed surgical procedure (Table 17-2). Unless there has been an intervening change in status, electrocardiogram and chest radiograph obtained within 6 months of the procedure need not be repeated. Likewise, chemistries and hemoglobin/hematocrit values obtained within 1 month are acceptable in the stable situations. Coagulation studies should be no more than 1 week old.

TABLE 17-2 Appropriate Preoperative Laboratory Tests Based on Patient History and Physical Examination*

The definition of advanced age is vague and should be considered in the context of that patient’s overall health.

* At least 50% of the task force experts agreed that the listed tests were beneficial when used selectively. Because of a lack of solid evidence in the literature, these indications are somewhat broad and vague and limit the clinical use of the guidelines.

8 What is the generally accepted minimum hematocrit for elective surgery?

There is no specific minimum; it depends on the clinical setting. Screening baseline hemoglobins for surgeries without significant blood loss do not add any value to estimations of perioperative risk or adverse outcomes. The potential blood loss and oxygen demands associated with the proposed surgical procedure must be considered, as well as patients’ medical conditions that may place them at increased risk for ischemia, including coronary atherosclerosis, cerebral insufficiency, or renovascular disease. Patients with advanced pulmonary disease also tolerate anemia poorly. Elderly patients with anemia often have a poorer functional status, longer hospitalizations, and higher mortality at 1 year.

9 Are there ways of predicting which patients will have pulmonary complications?

Among the most common risk factors for postoperative pulmonary complications (PPCs) is chronic obstructive pulmonary disease and advanced age; a more complete list of risk factors is in Table 17-3. Fortunately the more commonly seen PPCs rarely result in postoperative mortality; thus most surgeries may be performed even when these risk factors are present.

TABLE 17-3 Risk Factors for Postoperative Pulmonary Complications

COPD, Chronic obstructive pulmonary disease; OSA, obstructive sleep apnea.

From the New York Heart Association (NYHA).

Indications for pulmonary function testing are addressed in Chapter 9.

10 When are preoperative consultations with other specialists indicated?

Preoperative consultations fall into two general categories:

Those cases that need more information or expertise to establish or quantify a diagnosis that has implications for anesthetic management. An example is asking a cardiologist to evaluate a 50-year-old man with recent onset of exertional chest pain.

Patients in whom the diagnosis is known, but further evaluation and treatment are needed to optimize their medical condition before surgery. Referring patients with poorly controlled diabetes, hypertension, or asthma to an internist are examples.

11 What benefits and risks are associated with preoperative cigarette cessation?

All health care providers should take advantage of any opportunity to encourage patients to quit smoking. In years past various arguments were made to suggest that smoking cessation immediately before surgery increased certain perioperative risks such as increased airway irritability, diminished wound healing with nicotine replacement therapy, and increased patient anxiety associated with nicotine withdrawal. Most of these arguments have since been disproven and nonetheless pale in comparison to the overall health benefit of smoking cessation.

12 How long before surgery must a patient quit smoking to realize any health benefits?

All patients who smoke should understand that smoking cessation even immediately before surgery has profound, measurable health benefits. Nicotine is a stimulant and has a half-life of only 1 to 2 hours; its adverse effects on systolic blood pressure and heart rate can be seen after only 12 hours of smoking cessation. Carbon monoxide (CO), which diminishes oxygen-carrying capacity, has a half-life of only 4 hours. Diminished levels of nicotine and CO were likely behind the outcome of a study looking at episodes of ST depression in patients who smoked and underwent vascular surgery. This study showed that patients who smoked immediately before surgery had increased episodes of ST segment depression when compared to nonsmokers, prior smokers, and chronic smokers who did not smoke before surgery.

The longer a patient can abstain from smoking before surgery, the greater the perioperative health benefit: Bronchociliary function improves within 2 to 3 days of cessation, and sputum volume decreases to normal levels within about 2 weeks. A study of 120 orthopedic surgery patients randomized to receive an intervention to help them stop smoking 6 to 8 weeks before surgery saw a dramatic decrease in the overall complication rate in the smoking cessation group, mainly from diminished wound infections.

13 What are current guidelines for perioperative cardiac evaluation of patients scheduled for noncardiac surgery?

The American College of Cardiologists and the American Heart Association (ACC/AHA) have established an algorithmic approach to considering a patient’s cardiac risks before surgery, taking into account the urgency of surgery, the presence of active cardiac conditions (see Question 14), the invasiveness of the planned surgery, the patient’s functional status, and the presence of clinical risk factors for ischemic heart disease (see Question 15). Taken together, this algorithm underscores the importance of a history focused on cardiac issues for all surgical patients.

14 What are active cardiac conditions?

Active cardiac conditions are serious cardiac conditions that warrant immediate evaluation and treatment before undergoing surgery. There are four active cardiac conditions:

15 What are the clinical risk factors for a major perioperative cardiac event?

The Revised Cardiac Risk Index (Table 17-4) has six components: history of ischemic heart disease, history of congestive heart failure, history of cerebrovascular disease, preoperative treatment with insulin, surgical risk, and elevated preoperative serum creatinine. The patient is assigned one point for each of these risk factors, which are then translated into percentage risks of perioperative major cardiac events such as myocardial infarction, pulmonary edema, ventricular fibrillation, primary cardiac arrest, and complete heart block.

TABLE 17-4 Revised Cardiac Risk Index

Each of the following six risk factors is assigned one point. 1. High-risk surgical procedures Intraperitoneal Intrathoracic Suprainguinal vascular 2. History of ischemic heart disease History of myocardial infarction History of positive exercise test Current complaint of chest pain considered secondary to myocardial ischemia Use of nitrate therapy Electrocardiogram with pathologic Q waves 3. History of congestive heart failure History of congestive heart failure Pulmonary edema Paroxysmal nocturnal dyspnea Bilateral rales or S3 gallop Chest radiograph showing pulmonary vascular redistribution 4. History of cerebrovascular disease History of transient ischemic attack or stroke 5. Preoperative treatment with insulin 6. Preoperative serum creatinine >2 mg/dl

16 What constitutes the basic laboratory evaluation of coagulation status?

Chapter 7 reviews physical and historical information that might suggest disruption in coagulation. The basic laboratory evaluation includes platelet count, bleeding time, prothrombin time (PT), partial thromboplastin time (PTT), and thrombin time. The minimal number of normally functioning platelets to prevent surgical bleeding is 50,000/mm³. It is important to note that both the PT and PTT require about a 60% to 80% loss of coagulation activity before becoming abnormal, but patients with smaller decreases in function can still have significant surgical bleeding. Therefore the history is still very important. Thromboelastography measures the combined function of platelets and coagulation factors.

17 Are there special anesthetic considerations for surgical patients on warfarin?

Warfarin is a vitamin K antagonist and is used to prevent thrombosis and emboli. A patient on warfarin is at high risk for intraoperative bleeding. Before stopping a patient’s warfarin, it is important to know the indication for anticoagulation, the type and urgency of the surgery, and the consequences of intraoperative bleeding. Some patients are considered low risk for thromboembolism such as those with lone atrial fibrillation, and others are very high risk such as those with prosthetic heart valves. Patients who are at very high risk of thromboembolism but nonetheless need to discontinue their anticoagulant in the perioperative setting are often bridged with heparin, another much shorter-acting anticoagulant. Because warfarin has such a long half-life (about 2.5 days) and heparin has such a short half-life (about 1.5 hours), a patient may be instructed to stop warfarin 4 days before surgery and then, often as an inpatient, undergo regular heparin injections up until a few hours before surgery. Once the surgery is completed (and depending on the postoperative bleeding risk), the warfarin can be restarted.

18 What are considerations for patients with coronary stents?

Coronary stents, which are small metal mesh tubes that hold stenosed coronary arteries open, fall into two broad categories: bare metal stents and drug-eluting stents. The latter slowly release a chemical that helps prevent endothelialization. An ongoing debate among cardiologists is how long after stent placement a patient should remain anticoagulated. This is discussed further in Chapter 33. This anticoagulation issue adds considerably to the complexity of recommending cardiac workups for patients undergoing surgery.

19 A 3-year-old child presents for an elective tonsillectomy. His mother reports that for the past 3 days he has had a runny nose and postnasal drip. Should you postpone surgery?

Viral upper respiratory infection (URI) alters the quality and quantity of airway secretions and increases airway reflexes to mechanical, chemical, or irritant stimulation. Some clinical studies have shown associated intraoperative and postoperative bronchospasm, laryngospasm, and hypoxia. There is evidence that the risk of pulmonary complications may remain high for at least 2 weeks and possibly 6 to 7 weeks after a URI. Infants have a greater risk than older children, and intubation probably confers additional risk.

Young children can average five to eight URIs per year, mostly from fall through spring. If a 4- to 7-week delay for elective surgery were rigorously followed, then elective surgery might be postponed indefinitely. Therefore most anesthesiologists distinguish uncomplicated URI with chronic nasal discharge from nasal discharge associated with more severe URI with or without lower respiratory infection (LRI). Chronic nasal discharge is usually noninfectious in origin and caused by allergy or vasomotor rhinitis. An uncomplicated URI is characterized by sore or scratchy throat, laryngitis, sneezing, rhinorrhea, congestion, malaise, nonproductive cough, and temperature <38° C. More severe URI or LRI may include severe nasopharyngitis, purulent sputum, high fever, deep cough, and associated auscultatory findings of wheezes or rales.

It is generally agreed that chronic nasal discharge poses no significant anesthesia risk. In contrast, elective surgery is almost always postponed in children with severe URI or LRI. Most anesthesiologists will proceed to surgery with a child with a resolving uncomplicated URI unless the child has a history of asthma or other significant pulmonary disease.