Major infections worsened mortality rates in patients undergoing cardiac surgery

Major infections substantially increased mortality after cardiac surgery, according to a new study.

Researchers prospectively examined the frequency of postoperative infections and associated mortality, and they identified practices that were predictive of infections within 65 days of cardiac surgery.

The study enrolled 5,158 patients who underwent any type of cardiac surgery at one of 10 Cardiothoracic Surgical Trials Network sites from February 2010 to October 2010. The primary endpoint was onset of one of 10 major infections within 65 days of index cardiac surgery.

The infections included: deep incisional surgery site infection at the primary incision or a secondary incision site, mediastinitis, infectious myocarditis or pericarditis, endocarditis, cardiac device infection, pneumonia, empyema, C. difficile colitis and bloodstream infection.

Risk factors for infection

Nearly 5% of patients experienced major infections. The following baseline characteristics were linked to higher risk for infection: chronic lung disease (HR=1.66; 95% CI, 1.21-2.26), HF (HR=1.47; 95% CI, 1.11-1.95) and longer surgery (HR=1.31; 95% CI, 1.21-1.41), according to data reported by Annetine C. Gelijns, PhD, from the International Center for Health Outcomes and Innovation Research in the department of health evidence and policy at the Icahn School of Medicine at Mount Sinai, and colleagues.

Prophylaxis with second-generation cephalosporins reduced the risk for infection (HR=0.7; 95% CI, 0.52-0.94) and high levels of hemoglobin were protective against infection (HR=0.9; 95% CI, 0.84-0.97).

According to the researchers, practices and conditions associated with increased infection risk included:

Postoperative antibiotic duration of more than 48 hours (HR=1.92; 95% CI, 1.28-2.88). By contrast, compared with antibiotic duration of 24 to 48 hours, duration of less than 24 hours was not associated with increased infection risk (HR=1; 95% CI, 0.72-1.38).
Stress hyperglycemia (HR=1.32; 95% CI, 1.01-1.73).
Intubation time of between 24 and 48 hours (HR=1.49; 95% CI, 1.04-2.14).
Ventilation time of more than 48 hours (HR=2.45; 95% CI, 1.66-3.63).

Blood transfusion during surgery conferred an elevated risk for infection after all surgery types, except procedures involving left ventricular assist devices (HR=1.13; 95% CI, 1.07-1.2), according to the researchers.

Patients who contracted major infections had a much higher mortality rate compared with those who did not (infected patients, 5%; noninfected patients, 0.7%; HR=10.02; 95% CI, 6.12-16.39).

Other factors associated with an adverse effect on survival in the study population included higher creatinine (HR=1.17; 95% CI, 1.06-1.29), HF (HR=2.09; 95% CI, 1.34-3), diabetes (HR=1.65; 95% CI, 1.08-2.51) and older age (HR=1.04; 95% CI, 1.02-1.06). Men had half the mortality risk of women (HR=0.49; 95% CI, 0.33-0.72).

The 30-day readmission rate for the study population was 14%, whereas the 65-day readmission rate was 19%. Infectious accounted for 16% of readmissions, according to the study.

More surgical site infections prevented

In an invited commentary, Olaf Wendler, MD, PhD, and Max Baghai, PhD, wrote that these findings are an indicator of improvements in prevention of surgical site infections, which comprised a small portion of the infections in the study population. They noted that 79% of the major infections observed were pneumonia, bloodstream infections and C. difficile colitis.

The study also has implications for the reimbursement climate, in which payments are being increasingly tied to post-surgical outcomes, according to Wendler and Baghai, both from the department of cardiothoracic surgery at King’s College Hospital/King’s Health Partners, London.

“These data come at the right time as [payment by result] is more frequently discussed, highlighting the challenge of fitting high-risk patients into these new reimbursement arrangements, without first addressing their individual risk profile or overlooking their medical needs,” they wrote.

For more information:

Gelijns AC. J Am Coll Cardiol. 2014;64:372-381.

Wendler O. J Am Coll Cardiol. 2014:64:382-384.

Disclosure: The study was funded by the NHLBI, the National Institute of Neurological Disorders and Stroke, and the Canadian Institutes of Health Research. Several researchers report financial ties with Backbeat Medical, Bayer, Heartware, InHealth, Somahlution and Thoratec. Wendler and Baghai report no relevant financial disclosures.