Question 5

College answer

Syllabus topic/section:
2.1.5 Respiratory Intensive Care / Pleural disease and pleural drain management: L1
2.1.19 Intensive Care procedures / Respiratory, pleural drainage: L1

Discussion: Part A was done well by candidates with most displaying a knowledge of causes and familiarity with Light’s criteria.
Part B was noted for some candidates misreading the question as it asked for additional investigations to request on the pleural fluid. Candidates wasted time providing an extensive list of imaging and blood tests which was not required, rather than Pleural fluid ph and glucose, cytology and culture.
Therapeutic options for drainage of complex collections included a discussion of tube thoracostomy, Interpleural fibrinolytic therapy and video assisted thorascopic surgery.
The marking rubric for part c) is included to aid candidates' future study.

Domain	Below Standard	At standard	Above standard
c. (3 therapeutic options listed below) Tube thoracostomy (2 marks)	Not mentioned 0 marks	Reasonable answer. Does not include likelihood of failure in this patient. 0.5-1.0 marks	Nuanced understanding including current practice of not using large bore ICCs and the likelihood of failure as a sole therapy in complex effusions. 1.5-2.0 marks
c. Intrapleural fibrinolytic/mucolytic (1.5 marks)	Not mentioned 0 marks	Reasonable answer Mentions thrombolytic only 0.5- 1.0 marks	Nuanced understanding. Includes fibrinolytic/mucolytic combination and benefits. 1.5 marks
c. VATS (1.5 marks)	Not mentioned 0 marks	Reasonable answer with some understanding of the indications for surgery 0.5- 1.0 marks	Nuanced understanding. Includes indications for surgical referral 1.5 marks

Discussion

The inclusion of the rubric is refreshing, because the candidates need to be faced with the words "nuanced understanding" appearing three times in the "Above standard" column to really impress on them that the college is looking for a future colleague with a refined and subtle appreciation of pleural fluid. 

a) Likely causes:  no number of causes was specified and therefore one could theoretically produce twenty, but certain usual suspects present themselves from the characteristics of the fluid, which is exudative by Light's criteria:

• The fluid to serum protein ratio is greater than 0.5 (in fact it's 3.9)
• The fluid LDH is well over 200 IU/L
• the fluid LDH to serum LDH ratio is greater than 0.6 (in fact, 3.2)

Causes of exudative effusion are many, but only the following common causes stand out:

• Malignancy
• Parapneumonic effusion
• Decomposing haemothorax
• Empyema
• Autoimmune causes: RA, SLE, etc
• Tuberculosis
• Pancreatitis
• Pulmonary infarction following PE

b) List and explain additional investigations

What else can you run on pleural fluid?

• Glucose:  an extremely low pleural fluid glucose suggests that something is consuming it. Low pleural fluid glucose suggests TB, pneumonia or malignancy.
• pH: this is a weird one. Everybody orders pleural fluid pH, and few understand what significance it has. According to the 2000 guidelines from CHEST, pH can determine the need for therapeutic drainage. Anormal pleural pH is about 7.60; a pH of <7.20 is equivalent to a positive gram stain in terms of identifying an effusion which requires drainage. Oesophageal rupture can also cause a low pleural pH.
• Amylase:  this is elevated in pancreatitis-related effusion and in oesophageal rupture
• Cholesterol: this reveals the effuion as a chylothorax
• Cell count is already done, but cytology is not, which would be relevant if one seriously had malignancy in the list of investigations. Moreover the overabundance of, for example, eosinophils would be an unexpected and potentially game-changing finding.
• Culture is an expected normal destination for any body fluid sample retrieved in the ICU, and it is in fact surprising that some candidates for some reason omitted this obvious mark-scoring answer. Of course you would culture it, and of course it would probably grow nothing, for a variety of reasons

c) Discuss the therapeutic options for a complex pleural collection requiring drainage.

This resembles Question 4 from the second paper of 2022, where options for the drainage of empyema were asked for. But that was merely a "list the advantages and disadvantages". This is a "discuss" question that required "nuanced" etc. Still, on closer inspection of the vocabulary, one can see that "discuss" is in fact merely "list the advantages and disadvantages" with the extra steps of "underlying key principles" and "controversies".

Ergo:

• Principles:
  • A "complex" effusion (i.e the fibrinopurulent stage of empyema where multiple loculations are present) likely will not improve with conservative management
  • Drainage would ideally aim to drain all locules to prevent reinfection
• Options and their advantages/disadvantages:
  • IR-guided drainage and fine bore drain
    • The locules may communicate and late stage effusions may be thinner and less viscous, i.e. fine bore drains may still be effective
    • However, one drain is unlikely to achieve source control if there are many loculations, and multiple drains may be required
  • Wide bore drain
    • Considered the gold standard for viscous  fibrinous effusions
    • Not much benefit, when compared to fine bore tubes, and substantially more uncomfortable
  • Intrapleural fibrinolytics
    • Markedly improves rates of successful drainage, especially where loculations are beginning to form
    • May reduce need for surgical decortication
    • Risk of haemothorax is not zero
    • Inconsistent evidence of benefit (MIST1)
  • Thoracoscopic drainage
    • Breaks adhesions and allows drainage and correct tube placement
    • Shorter recovery time than decortication
    • Can be upgraded to decortication if a thick rind is discovered
    • However, to benefit, the patient has to be well enough for one-lung ventilation, and there is a greater risk of complications, because it is more invasive
  • Decortication
    • Removes all pleural infected tissue and allows the lung to reexpand; viewed as definitive
    • Relatively long recovery time (~ 7days)
    • Pain control is a major issue post-op
    • Large incision; unsuitable to patients with poor functional baseline
• Controversies and society opinions
  • fibrinolytic/mucolytic combination (5mg DNAse as dornase alfa, plus 10mg alteplase) seems to have greater efficacy than alteplase alone, in terms of hospital stay and radiological clearance, according to the MIST2 trial; however the cost of these agents is considerable (dornase alfa costs AUD $ 1490.98 per 15 intrapleural doses, and alteplase costs AUD $ 623.00 for a 10mg ampoule). 
  • The need for large-bore ICCs remains debated, and the guidelines recommend smaller tubes (14-16 Fr), even though they are known to fail sooner (8.1% vs 5.2% blockage rate, plus 42% vs 28% rate of "unintentional displacement").
  • The EACTS consensus statement on empyema suggests that all patients with Stage 2 and Stage 3 empyema be referred for surgery; but this statement is made on the basis of the observation that most studies reporting on the success of surgery in empyema enrolled Stage 2 and 3 patients. Moreover it is not clear whether VATS or decortication are the ideal solution.

This is more options than one could write in this short period of time, but the full version is offered to cover all possible variations of the answer for those playing at home. Note also that the effusion is "requiring drainage", which means candidates should not have wasted their marks comparing things to conservative management.