05 Preoperative

Cardiac Risk

An initial estimate of perioperative cardiac risk is calculated with the revised Goldman cardiac risk index (RCRI), which is based on the following 6 independent predictors:

• High risk surgery (intraperitoneal, intrathoracic, vascular)

• History of ischemic heart disease (MI within a month)

• History of congestive heart failure

• History of cerebrovascular disease

• Diabetes mellitus requiring insulin treatment

• Pre-operative creatinine >2.0 mg/dL

Total Points	Risk of Peri-operative Cardiac Complications for noncardiac surgery
Zero risk factors	0.4%
One risk factor	0.9%
Two risk factors	6.6%
Three or more risk factors	11.0%

Patients with a score of 1 or 0 on RCRI are considered low risk for major cardiac events (<1%).

Patients with low risk for major cardiac events can be cleared for surgery without further cardiac testing or risk stratification.

Patients with 2 or more RCRI are considered elevated risk for major adverse cardiac event.

Patients with an elevated risk of major adverse cardiac event need not require further cardiac testing if they have >4 metabolic equivalents (METs) which is considered moderate to excellent.

Functional status has been found to be an accurate predictor of perioperative and long-term cardiac events. Metabolic equivalents are measures of functional status estimated from activities of daily living and can be used to further risk stratify patients with elevated risk for major adverse cardiac events.

A question stem can provide information on a patient's functional status or METs implicitly. A patient who can perform the following or more should be understood to have adequate functional status and not require further testing:

• Climbing a flight of stairs

• Walking up a hill

• Performing heavy household work

• Rigorous sports activities

A patient with known or suspected heart disease should only receive a cardiac stress test or echocardiography before surgery if it is indicated in the absence of proposed surgery. Patients with the following conditions warrant further study:

• Unstable angina

• Significant arrhythmia

• Uncompensated CHF

• Severe valvular disease

Elective surgery should be delayed at least 8 weeks post-myocardial infarction.

It is recommended that an ECG be obtained in patients undergoing intermediate-risk procedures or in patients with at least 1 clinical risk factor identified by RCRI, in order to compare it to a postoperative ECG in the event the postoperative ECG is abnormal.

ECG is unnecessary in all patients undergoing low risk surgery (eg. cataract surgery).

MI

In pts with recent MI, postpone surgery if elective.

Hepatic

Child-Pugh score is used to predict mortality and short term survival in patients with liver disease. While the classification of patients based on the Child-Pugh score is beyond the scope of Step 2, the following measures of hepatic function are used in scoring:

• Albumin

• Bilirubin

• Encephalopathy

• Ascites

• PT (INR)

Mnemonic:"A BEAP"

Acute hepatitis is a contraindication for elective surgery.

Patients with liver disease should have their medical therapy optimized prior to undergoing surgery. The following should be evaluated in a patient with liver disease prior to surgery:

• Renal function

• Electrolyte abnormalities

• Bleeding time / PT (INR) / PTT

• Encephalopathy

• Nutritional status

If coagulopathy is present, attempt to normalize INR prior to surgery with:

• Vitamin K

• Fresh frozen plasma (FFP)

Prolonged bleeding time can be corrected in a patient with liver disease with desmopressin (DDAVP).

Patients who are taking warfarin should discontinue medication 3 to 4 days before the surgery. This timing is based on warfarin's half-life, which is approximately 36-42 hours.

For surgeries with a high risk of bleeding the international normalized ratio (INR) should be kept below 1.5.

A history of thromboembolism indicates anticoagulation with heparin or low molecular weight heparin (LMWH) (e.g. enoxaparin, dalteparin) after discontinuing warfarin until surgery then restarting warfarin postoperatively.

Heparin or LMWH is resumed 12 hours after surgery.

Diabetes

Patients with diabetes mellitus have the following surgical complications:

• Increased risk of infection

• Delayed wound healing

• Increase risk of cardiac complications

• Increased mortality postoperatively

Diabetic patients may require greater than normal insulin administration postoperatively due to glycemic fluctuations.

Nephropathy

Preoperative dialysis may be necessary for patients with renal insufficiency to control creatinine and electrolytes.

Acetylcysteine may be used to prevent contrast-induced nephropathy in patients with renal insufficiency, who are expected to receive intraoperative contrast. In addition, volume depletion and NSAIDs should be avoided. Isotonic IV fluid administration hours before can prevent volume depletion.

Nutritional Status

If the patient shows severe nutritional depletion, elective surgery should be postponed until optimized.

Severe malnutrition increases operative risk. Indicators of severe nutritional depletion include:

• Anergy to skin antigens

• Serum albumin < 3 g/dL

• Serum transferrin < 200 mg/dL

• Significant weight loss (e.g., loss of ≥ 20% total body weight) over a span of only a few months

The best lab test to determine acute nutritional status is prealbumin, due to its short half life (2-3 days). The normal range is 16-40 mg/dL. Values <16 mg/dL are associated with malnutrition.

However, prealbumin is expensive and may be decreased in patients with the following conditions:

• Physiological stress

• Infection

• Liver dysfunction

• Over-hydration

Pulmonary

Preoperative pulmonary function tests serve as the best predictors of postoperative pulmonary complications.

Patients with known lung disease (eg. COPD, asthma) and smokers should be considered for preoperative pulmonary function tests (PFTs) if after clinical evaluation it is still unclear whether the patient is at their best baseline and that airflow obstruction is optimally reduced. Routine PFTs in patients with stable symptoms and optimized management of their lung disease is NOT recommended.

The most effective way to reduce postoperative respiratory complications is smoking cessation at least 8 weeks prior to surgery.

A preoperative FEV1 of > 1.5 liters is required for lobectomy.

A preoperative FEV1 of > 2 liters is required for pneumonectomy.