Assessment and Minimization of Surgical Risk

During the preoperative period, comorbidities and other risk factors must be systematically evaluated, and a plan must be formulated to manage each during the perioperative period.

Age: Some studies show that age is an independent risk factor for postoperative death. Some physiologic changes that occur with aging (eg, decreased cardiopulmonary and renal reserve, slower wound healing) may increase surgical risk. Age may also be a surrogate for comorbidities. However, overall, age tends to predict outcome weakly and not as well as the patient's general health.

General health status: The American Society of Anesthesiologists Physical Status Classification (see Table 25-1), which is based on a patient's preoperative health status, is often used to predict surgical outcome. Age-adjusted mortality rates vary little among patients in classes I and II and only slightly among those in classes III and IV.

Functional status: All complications, including life-threatening ones, are more common among inactive patients. In one study, inactivity increased surgical risk almost 10-fold. Preoperative scores on activities of daily living instruments help predict the 1-yr survival of patients who have had a hip fracture.

Nutritional status: The mortality rate is significantly higher in patients who have lost > 20% of body weight before surgery. Nutritional status is assessed by standard instruments, such as the Mini Nutritional Assessment or Subjective Global Assessment. Serum albumin is measured in patients with chronic disorders, signs of undernutrition, or poor wound healing. A value < 3.5 g/dL indicates higher risk of complications and mortality but may not, by itself, correlate with nutritional status.

Many experts believe that nutritional support should be provided to all patients preoperatively, preferably using the GI tract, to the limit tolerated by the patient. Some data suggest that in severely malnourished patients, preoperative use of TPN decreases complication rates and does not increase infection rates. However, in most patients, TPN appears to increase infection rates without decreasing overall morbidity and mortality rates. Most experts agree that surgery should not be delayed to provide TPN preoperatively.

Psychologic and mental status: Social support systems and the will to live, although difficult to quantify, are important predictors of surgical outcome. Dementia increases risk of postoperative mortality (possibly up to 50%) and other complications.

Cardiovascular disorders: Cardiac complications, including MI, pulmonary edema, and serious arrhythmias, account for a large proportion of major surgical complications, including potentially preventable deaths. The Simple Index (see Table 25-2) is used to predict risk of complications. The best single predictor is the presence of coronary artery disease, particularly a recent MI. Other predictors include angina (particularly if severe), pulmonary edema (particularly if recent), valvular heart disease, and any cardiac rhythm (even premature atrial contractions) other than sinus rhythm, poor general health, age > 70, and need for emergency surgery.

Guidelines developed by the American College of Cardiology and the American Heart Association can help physicians evaluate perioperative cardiac risk and the need for additional evaluation or intervention in patients undergoing noncardiac surgery. The guidelines are based on clinical predictors (see Table 25-3), type of surgery (see Table 25-4), and functional assessment. Guidelines are frequently updated.

Heart failure should be corrected preoperatively to the degree possible. Preoperative symptoms of heart failure (eg, jugular venous distention, a 3rd heart sound) indicate increased risk of developing postoperative heart failure and pulmonary edema. K depletion due to diuretic use should be corrected preoperatively.

Hypertension should be controlled preoperatively, and antihypertensive drugs should not be stopped. During anesthesia, absolute reductions in BP are greater in patients with untreated or inadequately controlled hypertension than in those with adequately controlled hypertension.

Many cardiac drugs are myocardial depressants and interact with myocardial depressant anesthetics or other vasoactive drugs. Nonetheless, most cardiac drugs should not be stopped before surgery; sudden stopping, especially of  -blockers, may be dangerous.

Carotid artery disease: The influence of carotid artery occlusive disease on perioperative risk of stroke or death is uncertain. Overall perioperative risk appears to be increased in patients undergoing myocardial revascularization. However, in patients undergoing other types of surgery, risk may be increased only in patients who have had transient ischemic attacks or who have severe (eg, > 70%) occlusion of both internal carotid arteries or of both vertebral arteries. There is no convincing evidence that prophylactic endarterectomy in asymptomatic patients is beneficial before coronary artery bypass surgery or other procedures.

Pulmonary disorders: Pulmonary disorders account for a large proportion of perioperative complications and deaths. However, preoperative pulmonary function testing is usually needed only for patients who are undergoing thoracic surgery, who are heavy smokers, or who have symptoms or signs of a pulmonary disorder. Severe COPD (forced expiratory volume < 1.5 L at 1 sec) increases surgical risk, mainly because patients have an ineffective cough and cannot clear secretions. Other factors that increase risk of pulmonary complications include asthma, other pulmonary disorders, and chronic cigarette smoking.

Preoperative use of bronchodilators may reduce the bronchospastic component of pulmonary disorders. A few days of active physical therapy, including percussion and inspiratory exercises, may also be helpful. Smokers should avoid or minimize tobacco use preoperatively for up to 8 wk if possible. Use of inspirometers is widely recommended, but the benefit is unclear.

Liver disorders: Hepatic insufficiency usually results in a poor surgical outcome. Hepatic insufficiency is suspected based on history and sometimes on routine preoperative liver function tests. The only preoperative precautions that can be taken are correction of coagulation abnormalities with vitamin K or blood products (eg, fresh frozen plasma, coagulation concentrates).

Renal disorders: Renal insufficiency, particularly with uremia, increases surgical risk. In the elderly, the serum creatinine level must be adjusted for age and decreased lean body mass using one of several formulas.

Prerenal azotemia can often be corrected with IV fluids. Peritoneal dialysis or hemodialysis may alleviate uremia and reduce surgical risk. For all patients with renal insufficiency, including elderly patients with normal serum creatinine but reduced creatinine clearance, dosages of renally excreted drugs must be adjusted.

Thromboembolic disorders: The incidence of deep vein thrombosis is at least 20% for elderly patients undergoing general surgery and is higher for patients undergoing hip or knee surgery, neurosurgery, open prostatectomy, or a gynecologic cancer surgical procedure. The elderly are at increased risk of fatal pulmonary embolism postoperatively. Prophylactic treatment is indicated before any major surgical procedure. The treatment regimen varies with the type of drug used (eg, warfarin, heparin, various low mol wt heparins).

Drugs that increase bleeding risk: Patients taking warfarin or antiplatelet drugs are at increased risk of bleeding during and after surgery. However, stopping the drug may increase risk of thrombotic complications. Management is usually similar for elderly and younger patients.

Diabetes mellitus: Poorly controlled diabetes increases risk of perioperative infection. Perioperative stress increases production of counterregulatory hormones that increase plasma glucose (eg, catecholamines, cortisol, glucagon). Glucose should be monitored closely, at least immediately before surgery, at periodic intervals during surgery, and in the recovery room. Oral antihyperglycemic drugs should be stopped at least 1 day before surgery (3 days for chlorpropamide). Insulin-dependent patients can be treated with an IV insulin infusion. Alternatively, they can be given 1/3 to ½ their usual insulin dose on the day of surgery and 5 to 10 g of IV glucose/h; intravascular volume is controlled using fluids that do not contain glucose.

Long-standing diabetes increases risk of cardiovascular complications, possibly including silent myocardial ischemia. Patients should be monitored closely, and ECG should be done postoperatively.

This topic was last updated March 2006.