What Is a Lung Transplant?

Introduction

Lung transplantation is a well-known remedy for a few end-level pulmonary disorders. In 1981, the field of lung transplantation (LTx) was becoming advanced. Hundreds of pulmonary disease sufferers globally are candidates for a lung transplant because of respiratory failure – one-third have excessive COPD, and the other one-third have fibrotic lung disorders. The number of lung transplants has expanded more compared to transplants of other organs. More than 51,000 lung transplants have been done globally as of June 2014, as reported by the International Society for Heart and Lung Transplantation.¹

History

At the University of Mississippi in 1963, Dr. James Hardy and colleagues performed the first lung transplant procedure. The recipient had superior lung cancer and renal insufficiency, making them a less-than-perfect candidate, notwithstanding their COPD.²

Indications and contraindications relating to lung transplantation

Lung transplant indications can be broadly classified into four main categories of end-stage lung diseases:

• Vascular lung disease
• Fibrotic lung disease
• Septic lung disease 
• Obstructive lung disease

Lifelong observation and immunosuppression need to be given to those patients who undergo lung transplants. Lung transplantation will not be allowed for patients if they have a history of drug or alcohol abuse, mental health conditions that interfere with their ability to follow postoperative instructions or a lack of a strong social support system. 

Those with a previous history of cancer are also disqualified from lung transplantation, due to the requirement for lifelong immunosuppression, especially during the two years before a possible transplant. Persistent infection is a fundamental component of septic lung diseases and presents a challenge for these patients, and immunosuppression will amplify the infection. 

Potential contraindications for lung transplantation include patients with significant dysfunction of other vital organs. The most frequent concurrent organ dysfunction in the lung transplant population is cardiac dysfunction, which can be attributed to smoking, ageing and other causes.³

Choice of procedure

Bilateral (both) lung transplants account for about 75% of all lung transplants in the USA. Although certain diseases, like pulmonary hypertension or cystic fibrosis, require bilateral lung transplants, patients with advanced disease may need a single lung transplant. Furthermore, by using the lungs of a single donor to transplant two distinct recipients raises the effective transplantation rate. The choice between a single or bilateral lung transplant in patients is still controversial – however, the majority of large registry studies point to the benefit of bilateral lung transplantation for long-term survival.

On the other hand, individuals with COPD or pulmonary fibrosis who are only listed for a bilateral lung transplant without a single lung option may also be at a higher risk of dying while on the waiting list. Furthermore, the surgical risk associated with a bilateral lung transplant in people older than 75 may outweigh any potential benefits to long-term survival. When considered collectively, the data lend support to the practice of bilateral lung transplantation for the vast majority of lung recipients, with single lung transplantation being considered for individuals who are extremely elderly or have conditions that significantly raise the risk of surgery.⁴

Postoperative care and immunosuppression

After receiving standard ventilatory support, the majority of patients are extubated 24 to 48 hours after transplantation. Of lung transplant recipients, 10% to 20% experience early severe graft dysfunction, as evidenced by hypoxia and pulmonary hypertension. 

Several approaches have been devised to mitigate premature graft dysfunction. These include the utilisation of prostaglandin E₁ and oxygen-derived free radical scavengers. Inhaled nitric oxide enhances oxygenation and lowers pulmonary arterial pressure.

Compared to recipients of other organs, lung transplant recipients have several times higher infection rates, which are most likely caused by the graft's exposure to the outside world. Antibacterial prophylaxis is routinely administered to all patients. These antibiotics are adjusted if cultures of bronchial secretions from the donor or recipients show any indications of infection. The cytomegalovirus still poses a serious threat. The majority of programs have embraced the matching of seronegative donors and seronegative recipients as their approach. An intravenous or oral ganciclovir prophylaxis should be administered to other recipients.

To distinguish rejection from infection, radiographic, clinical, and physiological criteria have not proven adequate. A transbronchial lung biopsy has become the standard of care and provides a reliable and safe way to diagnose acute rejection.⁵

Postoperative surgical complications after lung transplantation

Airways complications

The incidence of airway complications ranges from 5 to 15%. It is more common in patients undergoing transplantation for infectious diseases like cystic fibrosis and bronchiectasis, where cultures reveal the presence of aggressive microbes like Pseudomonas and fungi like Aspergillus, Scedosporium, or Penicillium. These patients have a twofold increase in incidence, a higher risk of bronchial suture dehiscence, and more difficult management because of mucosal membrane inflammation and persistent secretions.

Vascular complications

Vascular complications occur in 1-3 percent of lung transplants. Nonetheless, there is a high death rate linked to these complications.

Venous suture complications encompass thrombosis and pulmonary vein obstruction. Lower pulmonary veins – specifically, the left lower veins – are more frequently affected because of their anatomical makeup. Usually developing within the first few hours following transplantation, pulmonary vein blockage is an early complication that results in severe symptoms. There are noticeable pulmonary oedema, pulmonary infiltrates, and hypoxia.

Pleural complications

The most frequent post-lung-transplant complication, that necessitates additional surgical procedures is haemothorax. Hemothoraces may develop immediately following the transplant procedure, a few days later, or several weeks later. Air leakage via chest drains is undesirable but is rare due to the meticulous nature of transplant surgery.

Damage to the graft during implantation or closure can inadvertently cause damage, as can donor lung removal, especially if the donor lung has pleural adhesions. A bronchoscopy is required to rule out bronchial suture dehiscence. Chest drains are usually left in place during conservative therapy.

Surgical wound complications

Complications from wounds are rare. Partial thoracotomy dehiscence can happen in patients undergoing single-lung transplantation, especially in those who are obese or who have taken high doses of steroids prior to transplant (for pulmonary fibrosis). Compression is used as therapy for minor dehiscences, and early reoperation is necessary for larger ones as well as those that affect cough and respiratory mechanics. Surgical wound haematomas are more common in patients undergoing antiplatelet or anticoagulant therapy prior to transplantation, and are typically caused by bleeding from small muscle vessels that have been cut through during surgery. A pressure dressing is part of the therapy; drainage is only necessary for haematomas of a significant size in order to avoid complications later on.

Abdominal complications

The most frequent reason for complications following thoracic surgery is emergency abdominal surgery. After lung transplantation, the incidence of postoperative emergency abdominal surgery can reach eight to ten percent..

Thirty to fifty percent of these cases have paralytic ileus, which can vary in severity. This is brought on by longer surgical times, the use of epidural analgesics after surgery, immunosuppressive medications, and abnormalities in the balance of water and electrolytes.

Gastroparesis is typically associated with medication, and vagus nerve injuries from surgery may exacerbate the condition. Recurrent vomiting brought on by undigested food being retained in the stomach can occasionally indicate persistent gastroparesis and a poor response to medical intervention. Commonly, acute cholecystitis first manifests itself in the postoperative phase. Cholelithiasis is frequently discovered in lung transplant candidates.⁶

Infection

The most frequent post-transplant complication and a significant contributor to morbidity and death is infection. Due to immunosuppression, lung denervation, loss of cough reflex, impaired mucociliary function, and lymphatic drainage patients are more prone to infection. After transplantation, bacterial infections are more common in the first four weeks and viral infections usually appear in the next month. Any time after transplantation, fungal infections can happen. Because trimethoprim- sulfamethoxazole prophylaxis is routinely used, Pneumocystis pneumonia is now rare.

Bacterial infections

At least half of all infections are caused by bacteria. Although the incidence peaks during the first month of the patient's life, it continues to be a major complication. 

Due to the widespread use of broad-spectrum antibiotics, deaths during the early postoperative period are uncommon. Gram-negative bacilli like Pseudomonas aeruginosa, Enterobacter cloacae, and Klebsiella organisms are the most frequently- occurring causative organisms. Additionally, gram-positive organisms like Staphylococcus aureus and Burkholderia cepacia are seen. These are linked to severe postoperative infections and lower survival rates in patients with cystic fibrosis.

Fungal infections

Fungal infections typically arise 10 to 60 days after transplantation, with Candida and Aspergillus organisms being the most common culprits. Compared to viral infections, they are less common but are linked to a higher mortality rate. The airways are often colonized by Candida species, although invasive pulmonary infection is rare.

Compared to other immunocompromised patients, lung transplant patients have a higher prevalence of aspergillosis. Aspergillus organisms causing localised or widespread infection are responsible for 2-33 percent of infections following lung transplants and 4 percent of all lung transplant-related deaths. Indolent pneumonia or fulminant angio-invasive infections with systemic dissemination can be caused by Aspergillus organisms.

Viral infections

The most frequent opportunistic infection and the second most frequent cause of pneumonia in lung transplant recipients is cytomegalovirus (CMV). With a peak incidence at 1-4 months, CMV pneumonia most frequently strikes children between the ages of 1 and 12 months..⁷

Summary

Lung transplantation is considered in cases of vascular lung disease, fibrotic lung disease, septic lung disease and obstructive lung disease. During the procedure, either one or both lungs may be transplanted. Post-operative care includes antibacterial prophylaxis and immunosuppression, which must be life-long. Like any major surgery, there are many potential complications, most commonly infections, but also complications arising from the radical nature of the surgery.