Mediastinitis – Comprehensive Medical Guide

Overview

Mediastinitis is an inflammation or infection of the mediastinum, the central compartment of the thoracic cavity that lies between the lungs. The mediastinum contains the heart, great vessels, trachea, esophagus, thymus, lymph nodes, and nerves. When bacteria, fungi, or sterile inflammation involve these structures, it can lead to severe illness.

The condition is relatively rare but carries a high mortality rate—especially the acute, postoperative form, where reported mortality ranges from 15 % to 40 % despite modern therapy [NIH, 2022]. Chronic mediastinitis, often caused by autoimmune disease or granulomatous infection, is less lethal but may cause progressive fibrosis and constriction of thoracic structures.

Who it affects:

• Adults aged 30–70 years are most commonly affected, largely because the majority of cases are postoperative after cardiac surgery.
• Men have a slightly higher incidence (approximately 60 % of cases) than women.
• Patients with a history of thoracic surgery, esophageal perforation, or severe trauma are at the highest risk.

Prevalence: In the United States, postoperative mediastinitis occurs in about 0.5 %–5 % of patients after median sternotomy for cardiac surgery [Mayo Clinic, 2023]. The overall incidence of all types of mediastinitis is estimated at 1–2 cases per 100,000 population per year worldwide.

Symptoms

Symptoms differ between acute (often postoperative) and chronic forms, but common features include:

• Fever & chills – Persistent temperature >38 °C (100.4 °F).
• Chest pain – Typically deep, retrosternal, and worsened by coughing, deep breathing, or swallowing.
• Difficulty breathing (dyspnea) – May be gradual or sudden, especially if a pleural effusion or airway compression develops.
• Hoarseness or voice changes – Resulting from recurrent laryngeal nerve irritation.
• Swallowing problems (dysphagia) – When the esophagus is involved.
• Persistent cough – Often productive if there is associated empyema.
• Fatigue & malaise – General feeling of being unwell.
• Weight loss – More common in chronic granulomatous mediastinitis.
• Night sweats – Seen in infectious etiologies such as tuberculosis.
• Skin changes over the sternum – Redness, warmth, or wound dehiscence after surgery.

In severe cases, patients may develop signs of sepsis (low blood pressure, rapid heart rate, altered mental status) or compressive symptoms such as facial swelling from superior vena cava syndrome.

Causes and Risk Factors

Primary causes

• Post‑operative infection – The most common cause, occurring after median sternotomy for coronary artery bypass grafting (CABG), valve replacement, or heart transplantation. Bacterial contamination often involves skin flora (Staphylococcus aureus, coagulase‑negative staphylococci) or respiratory organisms (Streptococcus spp., Gram‑negative rods).
• Esophageal perforation – From endoscopic procedures, severe vomiting (Boerhaave syndrome), or foreign body ingestion.
• Trauma – Penetrating or blunt chest injuries that breach the mediastinal fascia.
• Infections spreading from nearby structures – Such as deep neck infections, dental abscesses, or pulmonary infections.
• Granulomatous diseases – Tuberculosis, histoplasmosis, and sarcoidosis can cause a chronic, fibrotic mediastinitis.
• Autoimmune conditions – Rarely, diseases like rheumatoid arthritis may produce sterile mediastinal inflammation.

Risk factors

• Recent cardiac or thoracic surgery (especially median sternotomy).
• Diabetes mellitus or other conditions that impair wound healing.
• Obesity (BMI ≥ 30 kg/m²).
• Prolonged intubation or mechanical ventilation.
• Pre‑existing respiratory infection or colonization with MRSA.
• Immunosuppression (e.g., chemotherapy, corticosteroids, HIV).
• Alcohol abuse or smoking, which increase the risk of postoperative infection.
• Malnutrition or low albumin levels.

Diagnosis

Clinical assessment

Diagnosis begins with a thorough history (recent surgery, trauma, esophageal procedures) and physical exam. Key findings include fever, chest wall tenderness, sternal wound drainage, and signs of systemic infection.

Laboratory tests

• Complete blood count (CBC) – Often reveals leukocytosis with a left shift.
• Inflammatory markers – Elevated C‑reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are common.
• Blood cultures – Essential to identify bacteremia; positive in 30‑50 % of acute cases.
• Wound or mediastinal fluid cultures – Obtained via needle aspiration or during surgical debridement.
• Serology – For tuberculosis, histoplasmosis, or other specific pathogens when chronic disease is suspected.

Imaging studies

1. Chest X‑ray – May show mediastinal widening, sternal wire displacement, or pleural effusion.
2. Computed Tomography (CT) scan – The gold standard for visualizing mediastinal fluid collections, gas bubbles, soft‑tissue edema, and involvement of adjacent structures. Contrast‑enhanced CT improves detection of abscesses and vascular complications.
3. Magnetic Resonance Imaging (MRI) – Useful for assessing soft‑tissue infiltration and distinguishing chronic fibrotic changes from active infection.
4. Ultrasound (including trans‑esophageal echo) – Helpful for guiding needle aspiration of fluid collections and assessing pericardial involvement.

Procedural diagnostics

• Fine‑needle aspiration or CT‑guided core biopsy – Provides material for culture, Gram stain, and histopathology.
• Endoscopic evaluation – Upper endoscopy (EGD) when esophageal perforation is suspected.

Treatment Options

General principles

Prompt, aggressive therapy is crucial because mediastinitis can progress to sepsis, multi‑organ failure, or death. Treatment usually combines broad‑spectrum antibiotics, surgical drainage, and supportive care.

Antibiotic therapy

• Empiric regimen – Start within 1 hour of diagnosis. Common choices:
  • Vancomycin + piperacillin‑tazobactam
  • Or linezolid + cefepime if renal dysfunction limits vancomycin use
• Targeted therapy – Tailor to culture results (e.g., MRSA, Pseudomonas, anaerobes). Typical duration is 4–6 weeks of intravenous antibiotics, often followed by oral step‑down if the infection is controlled.
• Adjuncts – Consider antifungal agents (e.g., fluconazole, voriconazole) if fungal infection is suspected, especially in immunocompromised patients.

Surgical management

1. Early debridement and drainage – Median sternotomy reopening, removal of infected tissue, and placement of drainage tubes. This reduces bacterial load and prevents spread.
2. Vacuum‑assisted closure (VAC) therapy – Negative‑pressure wound therapy promotes granulation and decreases infection rates.
3. Reconstruction – Use of muscle flaps (e.g., pectoralis major, rectus abdominis) to cover large defects and improve vascularity.
4. Minimally invasive approaches – Video‑assisted thoracoscopic surgery (VATS) may be used for localized collections.

Supportive care

• Hemodynamic monitoring and fluid resuscitation for septic patients.
• Oxygen supplementation or mechanical ventilation if respiratory failure develops.
• Analgesia (e.g., acetaminophen, low‑dose opioids) to control pain and enable deep breathing.
• Nutrition support – enteral feeding preferred; parenteral nutrition if the GI tract is not usable.

Lifestyle & adjunctive measures

• Strict glycemic control (target <140 mg/dL fasting) in diabetic patients.
• Smoking cessation – reduces wound infection risk.
• Physical therapy to maintain chest expansion and prevent atelectasis.

Living with Mediastinitis

Post‑hospital discharge checklist

1. Medication adherence – Finish the full antibiotic course; use a pill organizer or reminder app.
2. Wound care – Follow nursing instructions for dressing changes; keep drains clean and monitor output.
3. Activity restrictions – Avoid heavy lifting (>10 lb) and vigorous upper‑body exercise for 4–6 weeks.
4. Follow‑up appointments – Typically 1–2 weeks post‑discharge for wound assessment, then every 4–6 weeks until imaging confirms resolution.
5. Nutrition – High‑protein diet (1.5 g/kg body weight) to support healing.
6. Vaccinations – Ensure up‑to‑date flu and pneumococcal vaccines to reduce secondary infections.

Psychosocial considerations

Recovering from a serious thoracic infection can be stressful. Patients may benefit from counseling, support groups, or online communities focused on post‑cardiac surgery recovery. Addressing anxiety and depression improves adherence to treatment.

Red‑flag monitoring at home

• New or worsening fever (>38 °C) lasting >48 hours.
• Increasing chest pain, especially if radiating to the back or jaw.
• Rapid swelling, redness, or drainage from the sternum.
• Shortness of breath, wheezing, or feeling “tight in the chest.”
• Changes in mental status (confusion, dizziness).

Prevention

• Pre‑operative skin preparation – Chlorhexidine showers and intra‑operative antimicrobial‑impregnated sutures decrease infection risk.
• Antibiotic prophylaxis – A single dose of a first‑generation cephalosporin (cefazolin) within 60 minutes before incision; add vancomycin for MRSA carriers.
• Glycemic control – Keep blood glucose <180 mg/dL perioperatively.
• Smoking cessation – Stop at least 4 weeks before surgery; nicotine replacement therapy can help.
• Optimizing nutrition – Pre‑operative albumin >3.5 g/dL is associated with lower wound infection rates.
• Meticulous surgical technique – Adequate hemostasis, proper sternal wiring, and avoidance of excessive tissue trauma.
• Early mobilization – Encourages lung expansion and reduces pulmonary complications that can seed the mediastinum.
• Post‑operative wound surveillance – Daily inspection of sternal incisions for drainage or dehiscence, with rapid intervention if problems arise.

Complications

If mediastinitis is not promptly treated, several serious complications can develop:

• Sepsis and septic shock – Systemic inflammatory response leading to multi‑organ failure.
• Pericarditis and cardiac tamponade – Inflammation or fluid accumulation compressing the heart.
• Myocardial abscess – Direct infection of heart muscle, often fatal.
• Superior vena cava (SVC) syndrome – Compression of the SVC causing facial swelling and venous congestion.
• Bronchial or tracheal stenosis – Fibrotic scarring narrowing the airway.
• Esophageal fistula – Abnormal connection between esophagus and mediastinum, leading to recurrent aspiration.
• Chronic fibrosing mediastinitis – Progressive, dense scar tissue that can encase vessels and cause vascular obstruction.
• Re‑operation mortality – Re‑entry sternotomy carries higher risk than the initial surgery.

When to Seek Emergency Care

References

• Mayo Clinic. “Mediastinitis.” Updated 2023. https://www.mayoclinic.org/diseases-conditions/mediastinitis
• National Institutes of Health (NIH). “Post‑operative Mediastinitis.” 2022. https://www.ncbi.nlm.nih.gov/books/NBK559598/
• Centers for Disease Control and Prevention (CDC). “Surgical Site Infection (SSI) Event.” 2023. https://www.cdc.gov/ssi/index.html
• Cleveland Clinic. “Mediastinitis – Diagnosis & Treatment.” 2024. https://my.clevelandclinic.org/health/diseases/17938-mediastinitis
• World Health Organization (WHO). “Guidelines for the Prevention of Surgical Site Infection.” 2021. https://www.who.int/publications/i/item/9789241550050