Question 13

College answer

Syllabus topic/section:

2.1.5    Respiratory Intensive Care: Respiratory Failure: L1
2.1.5    Respiratory Intensive Care: Lung Transplantation: L2

Discussion: 

Candidates mostly did well in part a) and those that did particularly well had a good structure to their answer with causes divided into infectious and non-infectious. They provided a wide and appropriate list of relevant organisms that would be expected for an immunosuppressed patient, beyond just bacterial, viral and fungal. Candidates that did poorly failed to include non-infectious causes, in particular rejection or instead they mentioned GVHD or graft failure which are different processes.
Candidates that did well in part b) included details in the history about the transplant and immunosuppression and differentiated between the causes in their examination and investigations with an appropriate level of detail. Candidates that did poorly failed to consider transplant specific factors or listed a generic set of investigations without detail of how to differentiate between the causes. The instructions were specific as to this aspect of assessment required. Some candidates didn’t include all sections of assessment as defined by the glossary (history, clinical examination, and relevant investigations) which unfortunately meant they didn’t address all parts of the question.
 

Discussion

"Beyond just bacterial, viral and fungal" is where you have to go, considering this patient likely has no functional immunity in any meaningful sense. A "list" vocabulary item usually calls for a literal list; but where one encounters something worth four marks, one is obliged to leave something a little more organised. And certainly GVHD is something of a gaffe, as one does not normally expect the transplanted lung to suddenly turn on the recipient. Anyway, it appears that "infectious" and "noninfectious" were sound categories to apply:

Infectious causes of ARDS in the lung transplant recipient:

• Usual CAP organisms (S.pneumoniae, H.influenzae, mycobacteria)
• Resistant organisms like Klebsiella, Serratia, Acinetobacter, Stenotrophomonas
• Viruses (the usuals plus CMV, VZV, HSV, EBV)
• Intracellular opportunists such as Nocardia and PJP
• Reactivated formerly quiescent M.tuberculosis 
• Fungi and yeasts like Candida, Cryptococcus, Aspergillus 

Non-infectious causes of ARDS in the lung transplant recipient:

• Neoplastic (cancer is the second most common cause of death in this population)
• Drug-induced (immunosuppressant-induced)  pneumonitis, eg. due to a calcineurin inhibitor, cyclophosphamide or leflunomide
• Acute rejection (most common in the first year) or Chronic Lung Allograft Dysfunction (CLAD)
• Atelectasis due to sputum plugging or brochial anastomotic stenosis
• Aspiration 

Assessment:

History

• History  

  • Recent travel
  • Suspicious occupational or recreational history (birds?  dust? livestock? gardening? etc) 
  • Exposure to others with similar illness
• Noninfectious possibilities
  • Rash, join swelling, haematuria (suspicion of vasculitis)
  • Slow, long course
  • History of ineffective courses of antibiotics
  • Weight loss (malignancy) or gain (cardiac failure)
  • Spent some time recently without airway reflexes, for reasons? (aspiration)
• For the immunosuppressed patient, also:
  • History of immunosuppressant use and adherence
    • Levels?
  • Empirical prophylaxis use
  • Vaccinations (splenectomy?)
  • Recent drug changes (interactions?)
  • Intestinal unhappiness that might have resulted in the malabsorption of oral antirejection drugs

• Examination for  features of infectious illness:

  • Peripheral features of infective endocarditis
  • Pharyngitis
  • Purulent sputum
  • Shocked state, vasodilated
• Examination for features of noninfectious illness:
  • Multiorgan involvement
  • Extrapulmonary sources of inflammation, eg. pancreatitis, ischaemic limb, sore muscle compartments (polymyositis)
• Finding such as fever, rash, lymphadenopathy, splenomegaly, as well as ausculation findings, are sufficiently scattered across the diagnostic categories as to be entirely meaningless from a diagnostic standpoint
   

• Investigations would obviously include:

  • Unimaginative bloods: FBC, EUC, CMP, LFT, but especially the inflammatory markers such as procalcitonin WCC and CRP
  • Cultures of everything
  • Serology:
    • for atypical pneumonia (though, admittedly, convalescent samples will need to be collected to be absolutely sure, and by that stage these will be of largely academic interest)
    • donor specific antibody levels (for the lung transplant recipient)
  • Bronchoscopy for BAL culture, as well as to assess the appearance of bronchial mucosa, which can offer clues
  • Sputum for cell count and cytology (what if it's swarming with eosinophils?)
• PCR of the BAL sample, PCR for specific organisms:
  • abovementioned infectious differentials
  • culture for for common CAP encapsulated bacteria, like Haemophilus, as well as tuberculosis, Candida and Nakaseomyces.
• CXR but realistically also a CT chest
• TTE to rule out cardiac causes or vegetations
• Bronchial or lung biopsy (the gold standard to detect rejection)