Cardiac surgery is a procedure that can transform someone’s life for the better, especially for individuals with cardiac-related ailments. However, even so, there are risks associated with such procedures, and one of those risks is mediastinitis. This complication is quite rare but can be very serious following any heart surgery.¹ The incidence of mediastinitis following sternotomy ranges between 0.25 and 5%.^2,3

In this review, we will discuss mediastinitis, why it is a concern after cardiac surgery, and what can be done to prevent and manage it.

What is Mediastinitis?

An infection or inflammation of the mediastinum, the central chamber of the thorax that contains the heart and big blood vessels, is the hallmark of mediastinitis, a dangerous and sometimes fatal medical condition. Mediastinitis after Cardiac surgery can develop if bacteria/fungus enter the mediastinum through the surgical wound, leading to inflammation, abscess formation, and potentially, sepsis.⁴

There are three types of mediastinitis: postoperative, descending necrotising and fibrosing mediastinitis, and each has its own set of causative factors. The two common types of mediastinitis are postoperative mediastinitis and descending necrotising mediastinitis (acute), while fibrosing mediastinitis (chronic) is less frequent in occurrence.

The CDC defines mediastinitis as an infection with clinical manifestations of significant infection and involving the tissues of the mediastinum, either of the following diagnosis criteria:

• Microbiologic Evidence: Detection of organisms from mediastinal tissue or fluid using culture or non-culture-based methods aimed at clinical diagnosis or treatment
• Anatomic or Histopathologic Evidence: Gross anatomic or histopathologic evidence, of infection or inflammation in the mediastinal region
• Signs and Symptoms in Patients >1 Year: Fever >38.0°C, chest pain, or sternal instability, with either purulent drainage from the mediastinum or mediastinal widening on radiographic studies
• Clinical Findings in Patients One Year of Age or Younger Fever greater than 38.0°C, hypothermia less than 36.0°C, apnea, bradycardia, or sternal instability, with purulent drainage from the mediastinal area or mediastinal widening on radiographic studies

These proposed criteria are useful for identifying mediastinitis based on microbiological evidence, anatomical involvement, and clinical manifestations.¹

Why is mediastinitis a concern after cardiac surgery?

Although Mediastinitis is a rare condition affecting less than 3% of people after cardiac surgery, it is a fatal incidence and often increases postoperative recovery and hospitalisation time, mortality, and morbidity.¹ Thus, it is important to understand the risks and signs of mediastinitis, which is very essential in early diagnosis and treatment to improve results and avoid possible long-term consequences. 

Causes and Risk Factors

Common causes

Mediastinitis most often results as a complication of cardiac surgery, esophageal dilatation, and endoscopy, when accidental injury to the tissues of the mediastinum allows infection by bacteria or fungi. Staphylococcus aureus and coagulase-negative staphylococci are the leading etiological agents responsible for 60-80% of cases.^5,6,7

Risk factors

Several factors can increase the likelihood of developing mediastinitis after cardiac surgery:

Patient-related factors

Conditions such as diabetes, obesity, smoking & renal diseases can weaken the immune system and make patients more susceptible to infection.^8,9,2

Post-Operative factors

Prolonged perfusion time, and repeated operation are associated with a higher risk of mediastinitis.¹⁰ Additionally, improper surgical technique or postoperative wound care can contribute to development of this infection.¹¹

Signs and symptoms to watch for

Early detection of the signs and symptoms of mediastinitis is important for timely treatment. Overall symptoms usually appear after 5-15 days following surgery. The common warning signs include:

• Chest pain may be categorised by potential abnormality including pain or discomfort in the chest, particularly at or near the incision site
• Fever of either acute or chronic origin may signal infection and may be an early sign
• Signs of infection at the surgical site, such as redness, swelling, or discharge

How is mediastinitis diagnosed?

The diagnosis of mediastinitis is based on a combination of prompt clinical assessment, imaging studies, and laboratory tests:

• Clinical assessment: A thorough physical examination and review of the patient’s medical history are the first steps in diagnosing mediastinitis
• Imaging: Chest CT or X-rays may also show signs of infection, including mediastinal fluid collections or abscesses.¹² Techniques like PET scans and MRI offer more precise visualisation of mediastinal infections, particularly in complex cases where traditional imaging may not be sufficient
• Laboratory tests: The blood tests and cultures from the site of surgery will pinpoint the type of bacteria/ fungi causing the infection and will indicate the direction for effective treatment¹³

Treatment options

The treatment of mediastinitis typically includes surgical intervention and administration of antibiotics.

• Surgical intervention: This usually involves debridement, or the removal of the infected tissue to control the infection. Sometimes, it requires re-exploration and drainage of the mediastinum¹⁴
• Antibiotic therapy: Treatment of antibiotic infections generally involves immediate initiation of broad-spectrum antibiotics, which may be adjusted according to the results of the culture in the inclusion of specific antibacterial drugs against the infective agent
• Supportive care: People suffering from mediastinitis often require intensive care. Nutritional support is an integral part of therapy along with careful monitoring for complications¹⁵

Alongside these innovative treatment approaches are also being explored. Negative pressure wound therapy (NPWT) has shown promise in managing wound infections by promoting faster healing, while hyperbaric oxygen therapy (HBOT) and immunotherapy are emerging as supportive treatments that may improve outcomes for high-risk patients.

Prevention strategies

Preventing mediastinitis starts before the surgery and continues through the postoperative period:

• Preoperative care: Optimizing the patient’s health before surgery, such as controlling blood sugar levels in diabetics and managing other chronic conditions, can reduce the risk of infection¹¹ 
• Intraoperative care: Surgeons take numerous precautions during surgery, including maintaining a sterile environment and using prophylactic antibiotics to prevent infection¹⁶ 
• Postoperative care: Proper wound care, close monitoring for signs of infection, and early mobilisation can all help prevent mediastinitis¹⁷

Prognosis and long-term outlook

When treated promptly, people with mediastinitis heal and return to regular lifestyles without long-term consequences. However, this infection could be serious and might lead to some complications: it may prolong hospitalisation, involve additional surgeries, and, in rare cases, end in death. In principle, the prognosis depends on the overall health condition of the person, timeliness of the diagnosis, and the effectiveness of the treatment.

Summary

Mediastinitis is a serious but manageable risk following cardiac surgery. With an understanding of the causes, recognition of symptoms, and following recommended strategies for prevention and treatment, this complication can be appropriately minimised. Most patients recover with timely and appropriate management, thereby underlining the awareness and proactive measures in reducing the risk of mediastinitis after cardiac surgery. Whether yourself or a loved one is preparing or recovering from cardiac surgery, knowledge certainly makes all the difference in preventing complications like mediastinitis.