Empyema appears in the CICM exam mostly in the form of a differential for a persistent fever or a patch of radiological opacity. It became the topic of an SAQ for the first time in Question 4 from the second paper of 2022, which was half about drainage options, and half about the differences between vancomycin and linezolid for a specific indication.
For that rare exam candidate with enough time to read anything other than college exam papers and UpToDate, Bryant & Salmon (1996) give an excellent overview of the pathophysiology. For management questions, one could go to either the 2017 AATS guidelines, or, because we are a colony, to the 2022 BTS guidelines for the management of pleural disease.
"Empyema" just means "pus in a cavity", etymologically derived from puon (pus) and em (in something). The term is not exclusively restricted to the collections that form in the pleural cavity, and you can get subdural empyemas, gall bladder empyemas, uterine empyemas, bladder empyemas, joint empyemas and literally any other kind of word+empyema combinations where the author of the paper decided to use "empyema" instead of "collection" to describe the presence of pus in some previously empty real or potential space. The distinction between these terms appears to be entirely arbitrary and their patterns of use seem to depend mostly on local culture. Still, as the only college question to ever deal with this was asking about a pleural MRSA collection, from here forward the word "empyema" will mean "an infected pleural effusion".
So: this can form for a variety of reasons, which can be broadly separated into two main groups:
When one hears "empyema", one typically lunges for the antibiotics, but in fact it appears that there may be causes that are not ostensibly infectious, and there are mentions in the literature of empyemas which are due to inflammatory nonifectious causes. From Parta (2020), in "Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases":
Either way, the purulent pleural collection progresses through some predictable stages, the classification of which was created in the 1960s:
To this one could theoretically add "Stage 0: complicated parapneumonic effusion" as this is often the antecedent of Stage 1. These classifications remain relevant since the mid-20th century because each stage has slightly different management options available, which remain largely unchanged, and which are as follows:
How is it not just a pleural effusion of some benign cause? 20-40% of all inpatients with bacterial pneumonia end up developing effusions, but most of them don't go on to require decortication or chest drainage, so surely some of these patients don't have empyema per se, but just a pleural effusion with some increased protein and cellularity ? Well: features strongly suggestive of "proper" empyema include:
An uncomplicated parapneumonic effusion (i.e. one which is exudative but not infected) will likely have none of these features, and will usually resolve with antibiotics alone (i.e. the effusion goes away with the pneumonia).
"List your options for the drainage of the empyema including one advantage and one disadvantage each", asked Question 4 from the second paper of 2022. This assumes you have settled on drainage as the solution. For the purposes of converting this section into the answer, the content is offered in the form of a table, but expanded to include some of the conservative options, for completeness. The main sources for the advantages and disadvantages here were Light (2006), UpToDate, AATS and BTS.
Options | Advantages | Disadvantages |
Uncomplicated parapneumonic effusion |
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Antibiotics alone |
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Thoracocentesis |
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Fine bore drain |
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Empyema |
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Fine bore drain |
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Wide bore drain |
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Intrapleural fibrinolytics |
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Loculated organising empyema | ||
IR-guided drainage |
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Thoracoscopic drainage |
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Decortication |
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Open drainage (short tube + bag, or gauze packing) |
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It probably goes without saying that antibiotic therapy is essential irrespective of which drainage option one picks, and the duration of treatment increases by 1-2 weeks with each evolving stage of empyema, such that the uncomplicated parapneumonic effusion scarcely needs more antibiotics than the pneumonia that caused it, whereas a loculated organising empyema requires at least six weeks if not more. And the antibiotics may need to be different, as not all of them are equally well equipped to perform their role in the devascularised acidic cavity that's formed in your pleural space.
Which brings us to:
The antibiotic answers for CICM exam questions would most likely be derived from the Australian eTG (Therapeutic Guidelines) which means the standard choice of antibiotics for a bog-standard empyema would have to be:
But those are the usual community-acquired streptococci and staphylococci, or the random Kleb you might grow in the ICU. Question 4 from the second paper of 2022 had MRSA, which changes the antibiotic choices substantially. Specifically, the college asked about the advantages and disadvantages of vancomycin and linezolid for this indication. Theoretically other agents (teicoplanin, daptomycin, tigecycline, ceftaroline) could also be thrown in to the mix, which means future candidates may get some benefit from tabulating these as well, but for now this section will focus only on what the college asked:
Bryant, Richard E., and Christopher J. Salmon. "Pleural empyema." Clinical infectious diseases (1996): 747-762.
Shen, K. Robert, et al. "The American Association for Thoracic Surgery consensus guidelines for the management of empyema." The Journal of thoracic and cardiovascular surgery 153.6 (2017): e129-e146.
Parta, Mark. "Pleural effusion and empyema." Mandell, Douglas, and Bennett’s principles and practice of infectious diseases, ninth edition. Philadephia: Elsevier (2020): 914-25.
Light, Richard W. "Parapneumonic effusions and empyema." Proceedings of the American Thoracic Society 3.1 (2006): 75-80.
Shankar, S., et al. "Image-guided percutaneous drainage of thoracic empyema: can sonography predict the outcome?." European radiology 10 (2000): 495-499.
Rahman, Najib M., et al. "The relationship between chest tube size and clinical outcome in pleural infection." Chest 137.3 (2010): 536-543.
Maskell, Nicholas A., et al. "UK controlled trial of intrapleural streptokinase for pleural infection." New England Journal of Medicine 352.9 (2005): 865-874.
Wunderink, Richard G., et al. "Linezolid vs vancomycin: analysis of two double-blind studies of patients with methicillin-resistant Staphylococcus aureus nosocomial pneumonia." Chest 124.5 (2003): 1789-1797.