Preoperative Evaluation for Noncardiac Surgery
Venue: Annals of Internal Medicine

Although every surgical procedure carries some degree of risk, risk is usually relatively low. The goal of preoperative risk assessment is to identify procedure and patient factors that significantly elevate the risk for complications. Careful, directed preoperative evaluation enables implementation of strategies to mitigate risk. Risk Factors What is the risk for medical complications from surgery in healthy patients? Healthy patients have significant physiologic reserves and tolerate major and minor surgical procedures well. The risk for serious medical complications from surgery is less than 0.1% overall in healthy patients. When evaluating these patients before surgery, physicians should use a focused history and physical examination to predict risk for serious medical complications. From 2001 to 2006, data from the Internet Based Quality Assurance and Peer Review reporting system, which analyzes death associated with procedures performed in facilities approved by the American Association for Accreditation of Ambulatory Surgery Facilities, reported 23 deaths (0.002% in 1141418 outpatient procedures (1) How does the procedure influence risk for complications in healthy patients? The type of surgery influences the risk for complications independent of other patient factors. Various definitions of low intermediate and high risk procedures have been proposed (see the Box) (24) Perioperative Risk Classifi cations for Surgical Procedures Low <1% Superficial surgery Breast Dental Cataract Endoscopic Thyroid Gynecologic, minor Orthopedics, minor Urologic, minor (TURP, TURBT) Reconstructive/cosmetic Intermediate (1%5% Intrathoracic (nonmajor) Intraperitoneal (splenectomy, cholecystectomy) Carotid (CEA or CAS) Endovascular aneurysm repair (stents/coils) Head and neck surgery Neurologic or orthopedic, major (hip and spine surgery) Urologic or gynecologic, major Renal transplantation High >5% Aortic, major vascular surgery, peripheral vascular surgery Major abdominal surgery and prolonged procedures with large fluid shifts or blood loss (duodenopancreatic, liver resection, bile duct surgery, perforated bowel, total cystectomy) Esophagectomy Pneumonectomy Lung, liver, or pancreas transplantation Adrenal resection CAS carotid artery stenting; CEA carotid endarterectomy; TURBT transurethral resection of a bladder tumor; TURP transurethral resection of the prostate. Data from references 24. The incidence of surgical adverse events in a random sample of more than 14 000 patients ranged from 2.3% for a combination of relatively minor procedures to 18.9% for repair of abdominal aortic aneurysm (5) In a study of more than 400000 major surgeries done in the Veterans Health Administration in the 1990s, multivariate analysis showed that surgical complexity was the third strongest predictor of postoperative morbidity after low albumin and American Society of Anesthesiologists (ASA) class (6) The type of surgery also influences the risk for specific types of complications. Postoperative pulmonary complications occur in 10% to 40% of patients undergoing upper abdominal and thoracic surgery, but these complications are rarely reported in other types of surgery (7) Moreover, an analysis of 68 831 operations performed in Veterans Affairs hospitals found that perioperative morbidity and mortality varied widely by types of procedure, and comorbid conditions had a greater influence in some procedures than in others (8) How do underlying chronic conditions influence surgical risk? The more comorbid conditions a patient has, the higher the risk for perioperative complications. Increasing ASA class (Table 1) is associated with increasing morbidity and mortality (9) Overall, perioperative mortality is very low in ASA class I and II patients <0.1% but increases significantly in class IV and V patients. However, deaths attributable to anesthesia alone are extremely rare. A study of more than 1 million surgical discharges from U.S. hospitals estimated mortality risk from anesthesia to be 8.2 out of 1 million surgical inpatients, and this number was higher in men and in the elderly (10) Despite increasing patient baseline risk, perioperative mortality has declined significantly over the past 50 years. The American College of Surgeons developed multiple risk calculators for individual surgical procedures using the National Surgical Quality Improvement Program database. The newest calculator can be used for many surgical procedures across various surgical specialties and incorporates the specific surgical procedure based on Current Procedural Terminology code as well as multiple comorbid conditions in predicting mortality and various other postoperative complications (11) Table 1. American Society of Anesthesiologists Classification of Physical Status How do lifestyle factors influence risk? Lifestyle factors can play an important role in the risk for perioperative complications. Exercise Self reported ability to exercise is a strong predictor of perioperative medical complications. Perioperative cardiac and neurologic complications doubled in patients who reported an inability to walk 4 blocks or climb 2 flights of stairs, even after adjustment for age (12) In patients having procedures associated with pulmonary complications (thoracotomy, upper abdominal surgery) inability to climb 2 flights of stairs was associated with a positive predictive value of 82% for postoperative complications (13) Smoking Current smokers are at increased risk for perioperative pulmonary complications. Risk varies on the basis of pack years, respiratory symptoms, and history of emphysema or chronic obstructive pulmonary disease. Although earlier studies suggested that recent quitters might be at increased risk for postoperative pulmonary complications and that risk is reduced only after 8 weeks of abstinence from tobacco, more recent evidence suggests that cessation as few as 4 weeks before surgery can decrease postoperative complications (14) and each week of cessation increases the beneficial effects (15) Therefore, the preoperative visit is an optimal time for the physician to strongly recommend smoking cessation and offer behavioral support combined with nicotine replacement therapy or varenicline. Alcohol and other substances Preoperative alcohol consumption is associated with an increased risk for perioperative morbidity, including general infections, wound infections, and pulmonary complications (16) Higher alcohol use, defined as at least 24 g/d in women and 36 g/d in men, increases complication rates, and intake >60 g/d is associated with 1 increased mortality. During preoperative evaluation, patients should be asked about quantity of alcohol use, pattern, and time since last drink. Use of recreational drugs, such as cocaine, heroin, and stimulants, is associated with pulmonary and cardiac disorders that may affect management throughout the perioperative period. Are obese patients at elevated risk? Obesity is associated with diabetes mellitus, hypertension, and cardiovascular disease, which in turn increase overall surgical risk. Compared with normal weight patients, obese patients (body mass index [BMI] >30 kg/m2) particularly those with morbid obesity (BMI >35) and super obesity (BMI >50) may also be at higher risk for such postoperative complications as wound infections; pulmonary complications; difficulties with anesthesia; deep venous thrombosis; gastric reflux with aspiration of gastric contents; and in persons with BMI greater than 35, postoperative rhabdomyolysis (17) Because of these risks, certain obese patients may not be candidates for surgery in ambulatory surgery centers and may benefit by being scheduled for the hospital and even overnight observation (18) Differences in drug pharmacokinetics in obese patients and normal weight patients should be taken into account when the types and doses of anesthetic agents are being chosen.  The overall risk for serious medical complications from surgery is less than 0.1% in healthy patients. Comorbid conditions that increase this risk include ischemic heart disease, cerebrovascular disease, heart failure, diabetes mellitus, chronic kidney disease, bleeding disorders, and liver disease. Poor nutritional status, obesity, smoking, hazardous alcohol use, and illicit substance use also affect perioperative risk. Poor exercise tolerance is associated with perioperative cardiopulmonary and neurologic complications. The type of the surgery influences the risk for complications independent of other patient factors.  Who should undergo preoperative evaluation? All patients scheduled for surgery should be considered for preoperative evaluation. For very low risk procedures, such as dental extractions or cataract surgery, this evaluation may only involve the oral surgeon or ophthalmologist confirming the lack of significant risk factors. For minor surgery or for patients with no significant medical history, screening the patient by phone may suffice. For more complex procedures and for patients with significant comorbidities, evaluation by a physician experienced in preoperative assessment may be judicious. A screening triage tool may be useful in making this determination. What are the essential elements of a preoperative history and physical examination? It is essential to ascertain the patient's age; medication use; exercise tolerance; use of tobacco, alcohol, and illicit substances; and overall health, including comorbid conditions, reaction to past surgeries, and experience with anesthesia. The history should include information about the condition for which the surgery is planned and focus on risk factors for cardiac, pulmonary, and infectious complications and include a determination of a patient's exercise capacity and ability to perform activities of daily living. It is important to know whether a patient is pregnant.