Risk Indices in Perioperative Medicine: What Do They Tell Us?

Presentation at the 2013 Southern Hospital Medicine Conference reviewed the clinical application of several key risk indices, including the Revised Cardiac Risk Index and the Vascular Study Group of New England Risk Index.

During his presentation “Perioperative Medicine I” at the Southern Hospital Medicine Conference in New Orleans, Steven Cohn, MD, internist at the University of Miami Miller School of Medicine, discussed various risk indices and perioperative beta-blockers.

The Revised Cardiac Risk Index (RCRI) [developed in 1999 by evaluating nearly 2,900 patients] uses six independent factors to predict cardiac complications: high-risk surgery, history of ischemic heart disease, congestive heart failure, cerebrovascular disease, diabetes medications with insulin, and chronic kidney disease/preoperative creatinine >2.0 mg/dL. Having three or more risk factors indicates a patient has a 9-11% risk of major cardiac complications. The RCRI was again revised in 2013 by eliminating diabetes medications as a risk factor and adding GFR <30ml/min.

Newer risk indices have been developed since the RCRI from larger patient cohorts. The Vascular Study Group of New England Risk Index (VSG-CRI) predicts the risk of postoperative myocardial infarction (MI), congestive heart failure (CHF), or arrhythmia. It was developed in a cohort of 8,000 vascular patients and lists as risk factors age, coronary artery disease, CHF, COPD, insulin-dependent diabetes mellitus, smoking, long-term beta-blocker therapy, and creatinine levels no greater than 1.8.

The Gupta Perioperative Cardiac Risk Calculator came out in 2011. It was developed by evaluating more than 200,000 patients and is a better predictor for MI and cardiac arrest than RCRI or VSGNE-CRI. It consists of five parameters: type of surgery, dependent functional status, creatinine >1.5 mg/dL, physical status, and age.

The American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) Surgical Risk Calculator was first published in 2013. It was developed by evaluating 1.4 million patients and examines 21 preoperative factors to predict risk of eight postop complications, as well as the estimated length of hospital stay.

The Surgical Mortality Probability Model (S-MPM) of 2012 [developed from about 300,000 patients] is a relatively simple but accurate predictor of 30-day postoperative mortality risk from noncardiac surgery. It assesses physical status, procedure risk (low, intermediate, high), and whether the surgery is an emergency procedure or not.

Cohn also discussed the use of perioperative beta-blockers (BBs). He mentioned a recent scandal that discredited 2009 findings that beta-blockers protect the heart in patients undergoing noncardiac surgery. 2009 guidelines for such BB use have not been revised, however. The most recent studies have been mixed, but indicate that perioperative BBs increase the risk of stroke, but reduce the risk of MI. Mortality figures have varied, depending on the study and medication. Cohn said he believed that perioperative beta-blockers may be effective if: a patient is already taking them; they are used selectively (in patients with CAD, CVA, pulmonary artery disease, DM, hyperlipidemia, and/or surgery is high-risk); they are avoided in low risk patients, the elderly, and prior to CVA, sepsis, emergency surgery; they are started as early as possible, at a mid to high dose; they are titrated to control heart rate (55-70); etiology of postoperative tachycardia is carefully evaluated before increasing dose. Cohn also commented that bisoprolol and atenolol are preferred to metoprolol, and that BBs may be required indefinitely if a patient has indications.