The Goldman risk model determines cardiac risk for surgery. Point scores are assigned to each of nine clinical factors; patients are divided into four risk classes based on the total point score (Table 8.2).

The risk for perioperative respiratory complications can be gauged by combining findings on chest examination, chest X-ray, Goldman cardiac risk index, and the Charlson comorbidity index. Risk reduction strategies initiated preoperatively, such as smoking cessation, lung expansion teaching, chronic obstructive pulmonary disease (COPD) treatments, and asthmatic treatments, may positively influence outcome after surgery.

The American Society of Anesthesiologists (ASA) classification system (Table 8.3) was initially developed to alert anesthesiologists to preexisting diseases. It has also been used to estimate operative risk and correlates directly with perioperative mortality and morbidity. This classification scheme also correlates with perioperative variables such as intraoperative blood loss, duration of postoperative ventilation, and duration of intensive care unit (ICU) stay.

Abdominal surgery induces a catabolic response with stress hormone release and insulin resistance; therefore, nutritional parameters should be evaluated in certain chronically ill patients before surgery.

Protein catabolism may be accentuated by prolonged fasting and bowel preparation. Increased nutritional risk can influence postoperative morbidity and mortality and anastomotic leak rates.

The prognostic nutritional index (PNI) was devised in the 1970s to predict complications such as sepsis and death after surgery. The PNI evaluates four factors to predict complications (serum albumin, transferrin, triceps skinfold thickness, and cutaneous delayed-type hypersensitivity), but only albumin, transferrin, and delayed hypersensitivity are accurate predictors of postoperative morbidity and mortality. This index can theoretically be used to identify patients who may benefit from nutritional support in the perioperative period.

The Acute Physiology and Chronic Health Evaluation (APACHE) scoring system was initially designed to assess risk for ICU patients but has been extended to assess patients with severe trauma, abdominal sepsis, postoperative enterocutaneous fistulas, and acute pancreatitis and to predict postoperative outcome.

Scoring for emergency patients being admitted to the ICU is best performed before surgical intervention. This index does not take into consideration the nutritional status of the patient, extent of surgery, or cardiovascular findings that add to operative risk.

Several simpler scoring systems have been developed from the APACHE system, including simplified acute physiology score (SAPS), which uses 14 of the 34 variables, and SAPS II, which also takes into consideration the urgency of the procedure and any associated chronic medical illness.

The Physiological and Operative Severity Score for enUmeration of Mortality and morbidity (POSSUM) calculates expected death and expected morbidity rates based on 12 physiologic variables and 6 operative variables (Table 8.4).

Another modification of this index, the CR-POSSUM score, is advocated to assess the risk for patients undergoing major colorectal cancer surgery.

Assessment of specific organ systems may be necessary and should be done for patients with identified preexisting dysfunction. In general, age, history of chronic heart disease, renal disease, emergency surgery, and type of operation are predictors of the risk of mortality.

Fit, young patients undergoing minor and intermediate procedures do not need routine preoperative investigation, and, in the pediatric age group, a thorough clinical examination has been found to be of greater value than routine laboratory screening.

A good history and physical examination are more important than laboratory data in the development of a treatment plan for anesthesia.

Preoperative tests serve to complement the history and physical exam. They have been used to assess levels of known disease, detect unsuspected but modifiable conditions that may be treated to reduce risk before surgery or detect unsuspected conditions that may not be possible to treat, and therefore simply be baseline results before surgery.

Many patients undergoing minor surgery need minimal investigation, even if they have chronic medical conditions.

Review of current evidence indicates that routine laboratory tests are rarely helpful except in the monitoring of known disease states. New guidelines have a significant impact on reducing preoperative testing and have not caused an increase in untoward perioperative events.

Tests that need to be performed prior to major colorectal surgical procedures include hemoglobin for evidence of anemia and as a baseline level for postoperative management.

Renal and liver function tests are not routinely carried out.

Preoperative blood glucose determination is obtained in patients 45 years of age or older because current recommendations suggest screening of all over that age. In addition, impaired glucose control increases perioperative risks.

A urine pregnancy test should be considered for all women of childbearing age.

Coagulation tests are only indicated in patients on anticoagulation, with a family or personal history of bleeding disorder or those with liver disease.

Patients undergoing major surgery with a potential for blood loss should have a type and screen, even if transfusion is not expected. This may help to minimize the risk of later transfusion reaction.

EKG is indicated in male patients older than 40 years and females older than 50 years. Those with a history suggestive of cardiac disorders, myocardial abnormalities, valvular disorders, conduction disorders, and hypertension may benefit from more intensive investigation prior to elective colorectal surgery.