Question 4

A 60-year-old patient was admitted to the ICU 3 days ago with MRSA pneumonia. The patient is febrile, intubated and ventilated, with an FiO2 0.7 and a noradrenaline infusion at 40 mcg/min. The CT today shows bilateral lung infiltrates with a moderate left sided empyema.

a) List your options for the drainage of the empyema including one advantage and one disadvantage each. (50% marks)

b) Outline the advantages and disadvantages of intravenous Vancomycin vs intravenous Linezolid in this patient. (50% marks)

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College answer

Candidates scored well if they structured their answers to give a clear outline in part b). What was lacking in some answers candidates was knowledge around surgical options in part a).

Discussion

This table of options is an extended version which is included here to simply revision, rather than as a true "model answer"

Options for Draining (or Not Draining) an Empyema
Options	Advantages	Disadvantages
Uncomplicated parapneumonic effusion
Antibiotics alone	Usually enough (and the patient is already on antibiotics anyway for the pneumonia) Very few will go on to require drainage (~10%)	Effusion may become loculated with time (perhaps 48 hrs), making future drainage more difficult
Thoracocentesis	Diagnostic Easily repeatable	May recollect
Fine bore drain	May improve respiratory performance; May prevent infection of the pleural space	Not necessary in a large number of cases, and carries a risk of introducing infection into a previously sterile space
Empyema
Fine bore drain	Easily done at the bedside Better tolerated than wide bore drains Could be definitive in a large number of cases (78% in one series)	Easily blocked Easily displaced Could delay other definitive management
Wide bore drain	Good rates of source control Considered the gold standard for viscous fibrinous effusions	Not much benefit, when compared to fine bore tubes 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 Inconsistent evidence of benefit (MIST1)
Loculated organising empyema
IR-guided drainage	The locules may communicate and late stage effusions may be thinner and less viscous, i.e. fine bore drains may still be effective	Unlikely to achieve source control if there are many loculations Multiple drains may be required
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	The patient has to be well enough for one-lung ventilation Greater risk of complications, because 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
Open drainage (short tube + bag, or gauze packing)	Frees the patient from the suction system Allows outpatient management in some cases Eventually creates a skin-lined fistula, allowing drainage to complete slowly	This is in effect an open chest wound May cause pneumothorax Depending on technique, may require repair in the future

Vancomycin vs. linezolid:

Vancomycin:
- Advantages:
  - Pharmacologically inert, no drug interactions
  - Cheaper
- Disadvantages:
  - Narrow therapeutic index; requires monitoring
  - Requires IV access, ideally central venous
  - May be nephrotoxic
  - Requires adjustment in renal failure
  - Does not penetrate especially well into abscess cavities or lungs
Linezolid:
- Advantages:
  - No need for monitoring
  - Good oral bioavailability (i.e. an extended course can be continued orally after the IV period is finished)
  - Does not need adjustment for poor renal function, nor is it nephrotoxic
  - Penetrates well into abssesses and lungs
  - Superior to vancomycin in RCTs (eg. Wunderink et al, 2003)
- Disadvantages:
  - Has substantial drug interactions (eg. can cause serotonin syndrome)
  - More expensive as an IV formulation
  - Can produce thrombocytopenia

References

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