Tuesday, September 20, 2005

Predicting Infection Risk for Cardiac Surgery Patients
By Julie McKeel

Infection after cardiac surgery results in higher rates of illness and death, as well as higher costs. Researchers from the DCRI, Duke, and the Louisiana State University Health Sciences Center have developed a model that identifies cardiac surgery patients at high risk for infection. Targeting these high-risk patients for preventive treatment prior to surgery may help to reduce rates of major infection, according to a recent study published in Circulation.

Vance Fowler, MD

"There is a critical need to identify patients undergoing cardiac surgery who are at risk for major infections and to develop effective interventions to prevent these infections," said Fowler. "The purpose of the study was to create and validate a bedside scoring system to estimate patient risk for major infection after coronary artery bypass grafting."

Until now, no study has developed a simplified scoring system to estimate an individual patient's risk for major infection after coronary artery bypass grafting (CABG).

The authors used the Society of Thoracic Surgeons (STS) National Cardiac Database to evaluate major infection in 331,429 patients who had undergone CABG procedures from January 1, 2002, to December 31, 2003. They identified the frequency and factors of major infection after CABG, and converted these factors into a bedside scoring system of 12 variables to estimate a patient's risk of major infection after CABG.

The STS Database, established in 1989, collects cardiothoracic surgical data from almost two-thirds of all U.S. bypass procedures from more than half of all centers performing adult cardiac surgery. This data is sent to the STS Data Warehouse and Analysis Center at the Duke Clinical Research Institute where a series of data quality checks are performed before the data are aggregated into the national sample.

The study shows that major infection occurred in 11,636 patients (3.51%). Patients with major infection had significantly higher death rates (17.3% versus 3.0%) and longer hospital stays after surgery (47.0% versus 5.9%) than patients without major infection.

Major infection, the primary end point of this study, was defined as either surgical site infection or septicemia (blood poisoning) before discharge, and/or hospital readmission within 30 days of surgery for deep chest wound infection, leg wound infection, or blood poisoning.

The impact of obesity, diabetes, and congestive heart failure was significant because over one third of study patients had a body mass index greater than >30 kg/m2, one third had diabetes mellitus, and 18% had congestive heart failure. Given the epidemic proportions of obesity in the U.S., the significance of these risk factors for major infection after CABG will only increase.

According to the study, a relatively small number of patients undergoing CABG bear the majority of risk for major infection, high-risk patients are identifiable before surgery, and several of these risks can be decreased.

Strategies for decreasing risk might include weight loss and/or smoking cessation efforts, specific treatments such as vaccines aimed at preventing infection, and at-risk assessments to help identify these patients prior to surgery. This risk score accurately identifies high-risk patients who may benefit from treatments designed to reduce this devastating complication of cardiac surgery.

The DCRI's Sean O'Brien, PhD, Lawrence (Doc) Muhlbaier, PhD, Ralph Corey, MD, and Eric Peterson, MD, MPH contributed to this research, as did Bruce Ferguson, MD, from the Louisiana State University Health Sciences Center.

This work was supported by grant AI-059111 (Dr Fowler) from National Institutes of Health.

Doc Muhlbaier, PhD

Ralph Corey, MD

Eric Peterson, MD, MPH

Not pictured: Sean O-Brien, PhD