Despite preventive procedures and treatment for deep sternal wound infections, incidence and mortality rates remain high.
Research has shown that patients undergoing cardiac operations using sternotomy have a significant risk for sternal wound infection. Some of these wounds are superficial and can be completely eradicated with IV antibiotics and local wound care. Other wounds are deep sternal wound infections (DSWI), which can result in increased morbidity and mortality. Despite advances in prevention, in-hospital mortality rates associated with DSWI range between 7% and 47%. Some of these patients need additional surgery, including repeated debridement and major surgical reconstruction.
DSWI can also significantly impact patient prognosis and hospital finances. “Long-term survival is much lower for patients who have experienced DSWI, and excess costs can arise from antibiotic treatments, surgical procedures, and longer hospital lengths of stay,” explains Bedrudin Banjanovic, MD.
Risk factors for DSWI include patient-related, intraoperative, and postoperative factors. Patient and surgical risk factors contribute to the risk for DSWI after cardiothoracic surgery. In addition, due to challenges in diagnosing DSWI, managing these complications requires care from a multidisciplinary team of cardiothoracic surgeons, plastic surgeons, intensivists, infectious disease specialists, and microbiologists.
Examining DSWI Incidence & Risk Factors
Vacuum-assisted closure (VAC) therapy can be used to promote open wound healing by applying negative pressure to infected tissues. VAC is a promising approach for healing DSWIs because it increases wound blood flow, reduces bacterial loads, and enhances the formation of granulation tissue.
For a study published in Medical Archives, Dr. Banjanovic and colleagues sought to determine the incidence of DSWI and related risk factors among patients who underwent cardiac surgery with median sternotomy and VAC treatment. They also assessed microbiology findings and antibiotic therapy use.
The retrospective observational study was conducted from 2015 to 2020, and data were obtained from 15 patients with DSWI following open-heart surgery. Inclusion criteria were the incidence of DSWI after cardiac operation via median sternotomy and the availability of complete microbiological findings as acquired by a sternal swab. Exclusion criteria included incomplete clinical data.
The study included nine men and six women, with an average age of 66. Eleven patients underwent coronary artery bypass grafting (CABG) operations, two patients received CABG with aortic valve replacement, and two had valve replacement surgery operations. All individuals included in the study were considered elective surgery patients.
Obesity & Diabetes Are Risk Factors for DSWI
According to the study authors, the number of patients with DSWI represented 1% of all sternotomy patients during the study period. Scores on the Society of Thoracic Surgeons (STS) risk calculator were highest for patients in the non-VAC group; average STS scores were 22.6 for the non-VAC group and 16.6 for the VAC group.
“Our study confirmed that obesity and diabetes were risk factors for DSWI, a finding that has been seen in other research,” Dr. Banjanovic says.
The mortality rate for the entire patient population was 33.3%.
The investigation also examined the microbiological isolates of DSWI among patients receiving VAC and those not receiving VAC (Table). The leading isolated micro-organism was Enterococcus faecalis, which was isolated in six patients (27%). Other common isolated microorganisms included Klebsiella pneumonia in three patients (13%), Proteus mirabilis in 2 patients (9%), and Serratia Maecenas in two patients (9%). The presence of more than one isolated micro-organism in the treated wound was observed in 31% of patients.
Efforts Needed to Reduce High Incidence & Mortality
DSWI continues to be one of the more serious postoperative complications after median sternotomy in patients undergoing cardiac surgery, according to the study authors.
“Unfortunately, despite preventive procedures and treatment for DSWI, there are still high incidence and mortality rates,” Dr. Banjanovic says. “Interventions are needed to decrease the burden of DSWI for patients and the healthcare system.”
Dr. Banjanovic notes that the study showed good results with VAC therapy for DSWI but cautions that the investigation included a small number of patients. Further follow-up of patients with DSWI and their VAC treatment is recommended.
