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.
Complications
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.
Late
Complications
Infection
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.
Immunosuppression-related
complications
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.
Long-term
survival
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.
