Complications Of Lung Transplantation
Initial post-transplant management
The early management of patients post-lung transplantation involves limiting airway pressures (<35 mmHg) and physiotherapy to improve expectoration; tracheostomy may be indicated to facilitate tracheal toilet if prolonged intubation is anticipated. Fluid management aims to keep the recipient in a negative balance so as not to waterlog the lungs, and colloids may be preferred to crystalloids for the same reason.
The early complications following lung transplantation may be divided into four types.
1. Technical complications relating to the surgery
· Airway anastomosis – the bronchial anastomosis (or tracheal if heart–lung) was the Achilles heel of the lung transplant procedure. The bronchi derive a blood supply from bronchial arteries coming directly off the thoracic aorta; these are not usually reimplanted. The donor bronchi are hence ischaemic. Anastomosis close to the lung hilum, with a very short donor bronchus, largely eliminates disruption and its catastrophic consequences.
· Nerve injury – the phrenic nerve is prone to damage as it runs along the pericardium near the hilar structures. The resultant diaphragmatic dysfunction may result in collapse (and then consolidation) of the lung because full expansion on inspiration cannot be achieved.
· Pneumothorax may result from rupture of bullae or may signify an anastomotic breakdown of the airway. Diagnosis may involve bronchoscopy to verify the integrity of the anastomosis. Most air leaks post transplant are from the lung parenchyma.
· Haemothorax is particular common where the lung has been infected and stuck to the parietal pleura, making removal difficult and bloody.
· Atrial arrhythmias, such as atrial fibrillation, are common and reflect clamping the left atrium. Most resolve spontaneously or after cardioversion.
2. Lung complications
· Primary graft dysfunction is the most important complication after lung transplant. It is a type of acute lung injury affecting the donor lung(s) secondary to ischaemia/reperfusion of the graft and is characterised by:
Ø alveolar and interstitial peri-hilar infiltrates (representing fluid and inflammatory cells)
Ø decreased lung compliance as the lungs become stiffer
Ø deteriorating gas exchange.
Prolonged ventilation is required and nitric oxide and prostaglandins have been used. Extracorporeal membrane oxygenation may be required if gas exchange is very poor.
· Pulmonary infection is common, and related to several factors:
Ø prolonged intubation and ventilation of the donor, with colonisation
Ø prolonged intubation of the lung transplant recipient
Ø prior colonisation of the lungs/trachea, especially in cystic fibrosis
Ø impaired mucociliary ‘escalator’.
3. Extrathoracic complications
Gut complications are common and are of three sorts.
· Delayed gastric emptying, possibly related to vagal nerve damage; it may result in reflux and aspiration if not treated.
· Meconium ileus equivalent, a form of intestinal obstruction affecting patients with cystic fibrosis.
· Acute colonic pseudo-obstruction, which may result in colonic perforation if untreated. This particularly affects older patients with COPD.
4. Immunological complications
Acute rejection is the most common immunological complication. Occasionally in very debilitated patients, graft versus host disease may occur, where the lung has sufficient immune cells to mount an immune response against the recipient – this is also a rare complication of liver transplantation.
Beyond the first month viral complications become more important, particularly the following two viruses.
· Cytomegalovirus (CMV), which can cause a severe pneumonitis in CMV-naive recipients of lungs from a donor previously infected with CMV.
· Epstein-Barr virus, which is associated with post-transplant lymphoma.
Fungal infections may also occur some time after transplantation, of which aspergillus is the most serious.
Bronchiolitis obliterans syndrome (BOS)
This is the manifestation of chronic allograft rejection in the lung. It is characterised by increased breathlessness, deterioration of the pulmonary function tests (FEV1, FVC), and an obstructive picture on high-resolution computed tomography (CT) with bronchial dilatation and air trapping. Biopsy reveals obliterative bronchiolitis, where the bronchial epithelium is lost and the bronchioles are occluded by intraluminal granulation tissue. It may be a slow, insidious process, or occur rapidly following a stimulus. Risk factors include any precipitating lung injury, such as previous primary graft dysfunction, recurrent acute rejection, viral infection such as CMV, bacterial infection and gastro-oesophageal reflux disease.
As with other forms of transplant, the long-term complications of immunosuppressive drugs also affect lung transplant recipients, such as calcineurin inhibitor-induced renal impairment and diabetes.
The complications of being immunosuppressed also affect this group, with post-transplant lymphoma and other cancers being more common.
More than 80% of recipients will survive the first year post transplant, and around 50% of patients will survive 10 years. The best results are in younger patients with cystic fibrosis. Retransplantation of the lung is not commonly undertaken, because there is a severe shortage of donor lungs.