Intrathoracic organ transplantation has received little attention from the CICM examiners, with the exception of one SAQ ( Question 22 from the first paper of 2009) which asks the candidate to "discuss the clinical issues specific to the heart lung transplant" in a patient with pneumonia.
LITFL have an excellent lung transplant overview, with a focus on ICU-level management.
Additionally, there is a chapter on this topic in Oh's Manual (Ch.102, pp. 1053) put together by Macdonald and Jansz. It offers some blue boxes full of donation criteria, and a series of protocols detailing the exact doses and timings of the immunesuppressant medications and antimicrobial prophylaxis.
A more detailed summary of complications of combined heart and lung transplantation, focusing on the physiological derangements associated with a long-term transpant, is also available. Specifically, the infectious complications of heart-lung transplantation receive some attention in the Infectious Diseases part of the Required Reading section.
The following brief summary is an attempt to synthesise the most memorable points in Oh's Manual together with the pearls offered by LITFL.
Notes on lung transplantation
Survival rates for lung transplantation:
- 80% at 1 yr
- 53% at 5 yrs
- 30% at 10 yrs
- Median survival is 5.5 yrs
- The greatest improvement in survival since the 1980's has been in the first few months following transplant
Notes on lung donation:
- Mainly, they are from brain-dead donors (but about 30% are DCD)
- The lungs are resistant to up to 90 minutes of warm ischaemia, and DCD transplants tend to do surprisingly well.
- Evolution of ex-vivo lung preservation devices has resulted in improved protection from post-retrieval deterioration in donated lungs
Notes on transplantation:
- Rather than en-block transplantation with tracheal anastomosis, these days each lung is grafted individually.
- Sometimes it is performed with bypass; however in the absence of bypass the one newly grafted lung ends up taking the entire cardiac output while the other lung is being grafter- and that can be a delicate situation.
ICU management of the lung transplant patient
Idiosyncratic features of management:
- Early bronchoscopy is performed to check the anastomosis
- Chest drains are on continuous suction routinely
- Antibiotic prophylaxis is guided by pre-op sputum cultures
- Antifungal prophylaxis commonly consists of nebulised amphotericin
The patients end up extubated early - 24 hrs post-op
Specific issues of ventilation:
- The major goal is to protect the grafts from ventilator-induced injury
- FiO2 should be weaned aggressively
- Tidal volume should be under 6-8ml/kg
- Peak inspiratory pressure should be under 30 cm H2O
Specific issues in the single-lung recipient:
- PEEP should be limited to 10 cm H2O in single-lung transplant recipients, as the native lung will accept more of the pressure (it has better compliance)
- The patient should be positioned native lung down for the first 6 hours, so as to decreased blood flow to the graft (apparently this decreases the risk of pulmonary oedema, though some investigators have found no difference in oxygenation)
Idiosyncratic properties of the transplanted lung
- The lung is denervated:
- Cough reflex is lost - voluntary cough and chest physio are required
- Mucociliary clearance is poor
- Pulmonary vascular resistance seems unaffected
- The bronchial blood supply is sacrificed
- The donor bronchial vessels are not anastomosed, and the bronchi receive hypoxic pulmonary arterial blood, as well as diffused oxygen.
- Over the first month, collaterals form.
- The period of ischaemia can lead to a series of long term complications:
- Bronchial stenosis
- Bronchial anastomotic dehiscence
- The graft is highly susceptible to pulmonary oedema
- The lymphatic clearance of fluid is interrupted
- The capillary integrity is poor due to reperfusion injury
- The patient usually returns from theatre with 10-15% extra body mass, due to fluid
- Fluid management in ICU should therefore be intelligent and cautious
- Authors have commented on local strategies, which typically involve maintaining a forced diuresis aiming for a 1000ml negative daily fluid balance, while carefully watching the renal function (as it may suffer from all the calcineurin inhibitors).
Complications of lung transplantation
Primary graft failure
- "Acute non-immune-mediated injury"
- Essentially, ALI/ARDS of the graft, due to reperfusion injury
- Occurs within 72 hrs, in 25% of recipients
- Mortality is around 50%
- Treatment is supportive; there is nothing specific to offer. ECMO may be required.
- When mild, the findings are subtle, resembling a LRTI
- When severe, the clinical picture resembles ARDS
- Requires a bronchoscopic histological diagnosis
- Pulsed methylprednisolone is the treatment of choice
- Antibody-mediated rejection can occur very early (donor-specific antbodies) - this may require plasmapheresis.
Early surgical complications
- Breakdown of bronchial anastomosis, leading to mediastinitis
- Pulmonary venous anastomosis kink or clot (sudden massive pulmonary oedema results)
Late surgical complications
- Pulmonary arterial stenosis at the anastomosis
- Pulmonary venous stenosis at the anastomosis
- This is a bronchiolitis obliterans
- Most late transplant mortality can be attributed to this