Introduction

Postoperative mediastinitis is a severe, deep surgical site infection that occurs in the mediastinum, the central compartment of the thoracic cavity, after surgery, most commonly following surgery involving incision of the mediastinum, known as “median sternotomy,” in cardiac procedures such as coronary artery bypass grafting (CABG) or replacement of heart valves.

Nowadays, there have been ongoing advances in surgical technique, antimicrobial prophylaxis and care of patients, but postoperative mediastinitis remains a serious and potentially life-threatening complication. It continues to affect approximately 0.25–5% of patients, contributing significantly to postoperative morbidity, prolonged hospital stays, and increased healthcare costs.⁴

Staphylococcus aureus is the primary causative factor, with methicillin-resistant strains (MRSA) accounting for up to 80% of surgical site infections and associated with mortality rates as high as eleven times those of methicillin-sensitive strains.⁴

Furthermore, while bacterial infections predominate, fungal mediastinitis (though rare), represents a growing clinical concern, especially in transplant recipients and immunocompromised patients. 

Diagnosis is often delayed, and clinical presentation is frequently subtle, necessitating heightened vigilance and multidisciplinary management.³ In response, quality improvement initiatives such as targeted MRSA decolonisation, audit-driven feedback, and patient-centred education are vital components of modern preventive frameworks.^4,5

This article outlines current evidence-based strategies to reduce the incidence of postoperative mediastinitis, structured across key perioperative phases and supplemented by quality improvement and patient education measures.

Preoperative measures

A study was conducted to investigate how the length of hospital stay before surgery could affect mediastinitis in high-risk cardiac patients who are often hospitalised awaiting surgery, as well as to evaluate current risk factors for this complication. They found that a longer preoperative hospital stay was identified as a separate risk factor, which resulted in a 15% higher chance of developing mediastinitis for each week of stay. An extended preoperative hospital stay, in addition to standard risk factors, is a notable and potentially modifiable indicator for the onset of mediastinitis after cardiac surgery.

A correlation was found between preoperative hospital stay and the risk of mediastinitis, showing that a hospital stay of more than 7 days resulted in a 2.43 times higher risk compared to a stay of 4-7 days, which increased the risk by 1.39 times.

Research shows that prolonged hospitalisation before surgery increases the risk of mediastinitis, as indicated by both univariate and adjusted models.¹

Patient assessment

 Assess the patient's overall health, comorbidities (e.g., diabetes, obesity), and immunocompetence.

Preoperative optimisation

Ensure optimisation of chronic conditions (e.g., glycemic control in diabetes).

Screening for MRSA

 Perform screening for methicillin-resistant Staphylococcus aureus (MRSA) colonisation and decolonisation if necessary.

Intraoperative measures

Antimicrobial prophylaxis

Administer appropriate prophylactic antibiotics within the recommended time window before surgery.

Aseptic technique

Maintain strict aseptic technique throughout the procedure.

Skin preparation

Use effective antiseptic agents.

Surgical technique

Ensure meticulous surgical technique to minimise tissue trauma and contamination.

Patients without retrosternal mediastinal infection, but with new granulation tissue in unhealed sternal wounds, had necrotic tissue and some necrotic sternum removed. The bilateral pectoralis major muscles were then moved forward and joined to cover the sternal defect as a palliative measure.

In a study of 36 patients upon admission, 33 cases tested positive and 3 cases tested negative for bacterial culture in wound exudation samples. However, during the operation, it was noted that 26 patients did not have an infection behind the breast bone, but instead had new tissue forming in unhealed wounds in the breastbone area. A palliative cleaning was done, and the muscles in both chests were brought forward and joined together to fill the gap.

Apart from one patient who experienced suture rupture from lifting under the armpit on the 3rd day after surgery, all other patients had successful wound healing within 7-21 days post-surgery.

The remaining patients recovered from their injuries and returned to their regular routine. During treatment, patients with pectoralis major muscle inversion had a sunken defect in the local skin of their muscle, which was lower than the opposite side, while those with pectoralis major muscle propulsion and abutment treatment did not show any apparent thoracic deformity.²

Postoperative measures

Monitoring and surveillance

Implement a surveillance system to monitor surgical site infections, including mediastinitis, to identify and prevent these complications.

Early detection

Train healthcare personnel to recognise early signs and symptoms of mediastinitis.

Wound care

Implement standardised wound care protocols, including dressing changes and wound assessment.

Nutritional support

Optimising nutritional status postoperatively is very important to enhance wound healing and recovery.

During this 11-year research in busy cardiac surgery centres, the occurrence of fungal mediastinitis following heart surgery was minimal, making up approximately 0.05% of the total surgeries performed.

Our findings offer fresh perspectives on the existing research, as this study is the largest multicenter investigation on post-cardiac surgery fungal mediastinitis conducted to date. Fungal mediastinitis appears to be less aggressive than bacterial mediastinitis, as only half of the patients exhibit local signs at the time of clinical presentation. The diagnosis of fungal mediastinitis post-surgery tends to take longer than that of bacterial mediastinitis, with an average delay of 38 days.

Patients who exhibit signs of mediastinitis after surgery and have negative bacterial cultures should be closely monitored for fungal mediastinitis, especially if they have undergone heart transplantation. They observed a rising incidence of fungal mediastinitis after cardiac surgery from 2009 to 2019. Thirdly, our research specifically targeted fungal mediastinitis following cardiac surgery, meaning our findings may not apply to other types of postoperative mediastinitis, such as those following oesophageal or cervico-facial surgeries.³ 

Quality improvement initiatives

Despite advancements in prevention and treatment strategies, mediastinitis remains a significant and potentially deadly complication following median sternotomy, with a prevalence of 0.25-5%. Staphylococcus aureus is the primary microorganism responsible for wound infections in most cases, leading to as much as 80% of post-surgical mediastinitis. MRSA mediastinitis has a mortality rate up to 11 times higher than MSSA mediastinitis. Numerous research studies have focused on decolonisation strategies to reduce the risk of infection and the spread of the organism to others, given the connection between colonisation and subsequent infection.

Administering vancomycin directly to the affected area, along with IV antibiotics and careful management of blood sugar levels, has proven highly successful in significantly reducing the rate of sternal wound infections following cardiac surgery, potentially becoming a crucial component of a comprehensive prophylactic approach to prevent these infections.

Chronic fibrosing mediastinitis, also known as 'sclerosing mediastinitis,' is a slower-developing type of mediastinitis that typically arises as a result of granulomatous infections, often caused by Histoplasma capsulatum or, less commonly, Mycobacterium tuberculosis.

Complete removal of the breastbone and repositioning of the greater omentum from the abdomen to the chest; practical methods for treating severe mediastinal infection after heart surgery.⁴

Audit and feedback

Conduct regular audits of infection rates and provide feedback to surgical teams to inform their practices.

Adherence to protocols

Emphasise adherence to established guidelines and protocols for infection prevention.

Multidisciplinary approach

Foster collaboration among surgeons, infectious disease specialists, and nursing staff to optimise prevention strategies.

Patient education

Caring for your incisions after thoracic surgery

You will have multiple incisions following your thoracic surgery, where your incisions are placed hinges on the specific surgery you underwent. Incisions will be present at the surgical site and from the chest tube.

The nurse will remove the staples from your incision during your initial postoperative appointment if you still have them when you go home.

It is normal to experience lower energy levels than usual after thoracic surgery.

In addition, stretching exercises can assist in restoring complete arm and shoulder mobility following thoracic surgery. To help clear your mucus more easily after thoracic surgery, it is advisable to drink plenty of fluids to thin it out. Consult your healthcare provider about when you are allowed to drive following thoracic surgery.⁵

Summary

• Additional research is necessary to examine ways to reduce the waiting period for hospitalised patients in need of cardiac surgery and enhance antibiotic treatment to prevent mediastinitis, a modifiable risk factor
• Patients who show symptoms of mediastinitis following surgery and have negative bacterial cultures should be carefully watched for fungal mediastinitis, particularly if they have had a heart transplant
• As the study focused on fungal mediastinitis after heart surgery, the results may not relate to different types of postoperative mediastinitis after other surgeries, like oesophageal or cervico-facial ones
• Lastly, educating the patient: How to take care of your incisions following thoracic surgery. You will have multiple incisions following your thoracic surgery
• Dealing with fatigue after thoracic surgery is a common experience, resulting in lower energy levels than normal