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Hospital data helps predict risk of pneumonia after heart surgery

New risk model could help patients avoid a common postsurgical complication

ANN ARBOR, Mich. -- Pneumonia is the most prevalent infection following open heart surgery, leading to longer hospital stays and lower odds of survival. 

But a new analysis of data gathered about thousands of individuals who had coronary artery bypass graft surgery at Michigan hospitals revealed ways that patients can prepare their bodies to reduce the risk of postoperative pneumonia – a complication that occurred in 3.3 percent of patients included in the observational review.

In the current issue of Annals of Thoracic Surgery, investigators identify a list of 17 readily identifiable patient characteristics, age, race, smoking habits and white blood cell counts among them, associated with developing pneumonia after cardiac surgery.

Cardiac surgeons in Michigan and investigators at the University of Michigan Health System developed the list based on the experience of 16,084 patients that underwent cardiac surgery at 33 hospitals sharing data with the Michigan Society of Thoracic and Cardiovascular Surgeons Quality Collaborative.

The group’s findings have significant potential, says senior study author Donald Likosky, Ph.D., an associate professor of cardiac surgery at the U-M.

“This work reflects an evolution of our understanding of post-operative infections,” Likosky says, “and can go a long way to preserve resources and help patients recover from one of the country’s most common cardiac procedures.”

Study co-authors include cardiac surgeons at Henry Ford Hospital, Henry Ford Macomb Hospital and Bronson Methodist Hospital.

Proactive measures

A person’s health and habits are often good predictors of recovery.

The new preoperative risk model, then, is designed to guide clinical decision-making, as well as physician-patient conversations about regimens to pursue before an operation in order to avoid pneumonia later.

Such preventative strategies “may reduce a patient’s risk for postoperative pneumonia,” says Raymond Strobel, lead study author and a third-year medical student at the University of Michigan.

Which is why it’s crucial for doctors to know the study’s predictors that could signal signs of future trouble.

The key culprits:  admission for heart surgery via the emergency room; a history of lung problems; a long hospital stay prior to surgery, and low ejection fraction -- a measurement of how much blood is pumped out by the heart with each beat.

Another well-recognized risk for postoperative pneumonia is smoking, although quitting – even just a month before surgery – can help. Elevated white blood cell count, called leukocytosis, was also a significant predictor.

“Patients presenting with an elevated white blood cell count before their operation may be mounting an immune response against a pathogen or other challenge and CABG significantly increases their odds of post-operative pneumonia,” says study co-author Gaetano Paone, M.D., MHSA, a cardiac surgeon at Henry Ford Hospital, Detroit, Mich.

It may be in the patient’s best interest to delay surgery, if possible, to investigate the elevated white cell count, authors say.

In any case, the study underscores a continued need for vigilance – both before and after cardiac surgery.

The data on preoperative risk factors were first presented at the 62nd annual meeting of the Southern Thoracic Surgical Association.

The project was funded by the Agency for Healthcare Research and Quality, and Blue Cross Blue of Michigan supports the state quality collaborative.

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