Kate Johnson

September 08, 2014

WASHINGTON, DC — Presurgical depression is associated with an almost 3-fold risk for sternal wound infection after cardiothoracic surgery, which may lengthen hospital stay and result in rehospitalization and reoperation, according to the results of a new study.

"This type of infection can have serious consequences, so it is important to identify risk factors. If we can remove these risk factors, we can try to prevent infections in the future," said lead investigator Deborah Theodore, MD, from the Columbia University Medical Center in New York, New York.

"Depression is treatable and further research is needed to determine whether treating depression effectively can improve outcomes after cardiothoracic surgery," Dr. Theodore told Medscape Medical News.

The study results were presented here at the 54th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC).

The retrospective, case-control study included 129 patients (mean age, 67 years) who developed sternal wound infection after undergoing coronary artery bypass grafting, valve surgery, or aortic root surgery.

"Most infections were caused by gram-positive organisms, and most of those by staphylococci (48%), but gram-negatives also played their role, especially Pseudomonas (8%) and Klebsiella (12%)," said Dr. Theodore.

Each case was matched to 2 control patients (mean age, 69 years) who had undergone similar surgeries but experienced no infection. Cases were matched according to their date of surgery to account for any temporal infection trends within the hospital.

 
This was a stronger association than any other medical comorbidity. Dr. Deborah Theodore
 

Chart reviews were used to look at depression status and other risk factors for sternal wound infection. Variables collected included demographic characteristics, medical history, laboratory values, and intraoperative values.

Patients were classified as having depression based on a composite of the following: a recorded history of depression in the medical record before surgery; a preoperative International Classification of Diseases, Ninth Revision (ICD-9), code; a depressed mood on a preoperative mood screening; or any history of use of antidepressants within the past year.

The study found that people who reported depression were more likely to develop sternal wound infection than those who did not (21.7% vs 11.2 %; P = .006).

"Each one of the variables that made up the composite definition of depression was more prevalent among people who developed infection with the exception of the ICD-9 code," Dr. Theodore reported.

"Notably, of the 7 people who reported a depressed mood before surgery, 6 went on to develop infection (P = .007), suggesting that a depressed mood before surgery has a powerful influence," she added.

Indeed, reporting any abnormal mood before surgery was associated with an increased risk for infection (P = .002). On multivariable analysis, after adjustment for age and sex, the study found that depression conferred a 2.7-fold increased risk for sternal wound infection (P = .007).

"This was a stronger association than any other medical co-morbidity (heart failure OR [odds ratio] 1.8, body mass index OR 1.1) and was equivalent to the surgical variable of bilateral internal mammary artery use," said Dr. Theodore. Only intra-aortic pump use conferred a higher risk (OR, 3.6).

"Although the point of the study was not to look at the consequences of infection, we did collect some data and we found that people who had sternal wound infection had longer hospitalizations, more hospitalizations, more readmissions to the ICU [intensive care unit] and more reoperations," she said. "We also looked at the 25 people who had in-hospital deaths and 14 of them (10%) were cases compared to 11 (4%) of controls."

While acknowledging that the study shows only an association and not a causal effect, Dr. Theodore underscored the importance of presurgical depression in terms of risk for sternal wound infection.

"Over 85% of people who reported a depressed mood went on to develop an infection, which suggests that a simple mood screen could be a valuable tool in determining who might be at increased risk of infection," Dr. Theodore said.

But Jean-Jacques Parienti, MD, from Côte de Nacre University Hospital in Caen, France, urged caution in drawing conclusions.

Caution Advised

"The finding of an association is new and original, and the study investigators should be congratulated," he said, but he pointed out that controls were not matched for age or presence of chronic disease.

"Adherence to treatment of chronic diseases such as diabetes might contribute and the study did not control for this," he said.

"Multivariable analysis in such a small group might be problematic," Dr. Parienti added, suggesting that subgroup analysis might reveal other risk factors for sternal wound infection.

"We found similar results in a study looking at adults undergoing spine operations, and we were wondering if depression might affect the way people care for their surgical wounds or whether it might affect nutritional status," said session moderator Loreen Herwaldt, MD, from the University of Iowa College of Medicine in Iowa City.

Reached by Medscape Medical News for further comment, Janice Kiecolt-Glaser, PhD, director of the Institute for Behavioral Medicine Research at Ohio State University College of Medicine in Columbus, said, "The findings are quite consistent with considerable evidence from both humans and mice that stress slows wound healing."

Dr. Kiecolt-Glaser has published extensively on this topic, including a review on the impact of psychological stress on wound healing (Immunol Allergy Clin North Am. 2011;31:81-89).

"Slower wound healing enhances risk of infection," she told Medscape Medical News. "In addition, considerable evidence from both humans and mice shows that the cellular immune response, an important defense against infection, is also downregulated by stress and depression. So, we have a double whammy here: stress and depression slow wound healing and simultaneously dysregulate important immune responses related to infection control."

Dr. Theodore, Dr. Parienti, and Dr. Kiecolt-Glaser have disclosed no relevant financial relationships. Dr. Herwaldt has been a grant investigator for Deck2Walls, MicroDermis, and the Agency for Healthcare Research and Quality.

54th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC). Abstract K-570. Presented September 6, 2014.

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