Empyema: This is defined as collection of pus in a naturally occurring cavity and is a complication of pneumonia. Nb Empyemas do occur in the gall bladder and rarely an intracranial subdural empyema.
What is the difference between and abscess and empyema:
Empyemas are accumulations of pus from a pre-existing anatomical cavity
Vs
Abscess: accumulations of pus in a newly formed structure, formed by adjacent healthy cells in an attempt to keep the pus from infecting neighbouring cells
The four steps to Empyema:
- 1. Pneumonia
- 2. Simple parapnuemonice effusion
- 3. Complex parapneumonic effusion
- 4. empyema
- Pneumonia
- Simple parapneumonic effusion (a pleural effusion being excess fluid that accumulates in the pleural cavity results from inflammation of the pleura by the adjacent pneumonia infection. This infection causes increased capillary permeability and exudation of fluid into the pleural space. Initially the pleural fluid is sterile, so will appear clear with:
- low white cell count
- lactate dehydrongenase, LDH (low levels in a transudate – passive secretion and high levels in exudate as a result of inflammation)
- normal glucose and pH.
This simple parapneumonic effusion appears on a CXR or USS as a free flowing effusion.
- This develops into a complicated paraneumonic effusion as the fluid is invaded by the bacteria from the adjacent pneumonia. This leads to:
- Increased numbers of neutrophils
- Decreased glucose levels
- Pleural fluid acidosis
- Elevated LDH
It is classified as complicated because it requires drainage for resolution
- Empyema Thoracis: This develops as the complicated parapneumonic effusion fails to resolve and there is frank pus accumulation in the pleural space. The patient will appear:
- acutely unwell with a high fever
- elevated neutrophils = granulocytois
- marked elevation in LDH > 1000U/l
- Marked pleural fluid acidosis
- Marked decreased glucose level
Laboratory studies indicate that preexisting pleural fluid is required for the development of empyema because it is not seen after direct inoculation into a dry pleural space. The pus is seen after is has been removed by drainage of which there are various options which will be discussed bellow.
Treatment: IV augmentin TDS for 5 day + drainage
Nb Hippocrates in 500BC recognised the serious problem of empyema and recommended treating it with an open drainage
Risk factors for developing and empyema from pneumonia:
- Low albumin <30 g/l
- Low sodium <130 mmol/l
- Platlet count >400
- IV drug use
- Hx of alcohol abuse
- Hx of COPD
Pleural drainage:
- Thoracocentesis: a procedure to remove fluid from the pleural space and then used diagnostical to establish the cause of the pleural effusion.
- http://www.youtube.com/watch?v=noDxydboLrA
- Chest drain (tube thoracostomy): position tube under USS guidance in a dependent part of the empyema. The key to this procedure is prompt drainage. There are two techniques:
- Guide-wire assisted serial dilation
- Cut-down approach – blunt dissect and then drain
- http://www.youtube.com/watch?v=noDxydboLrA
Recent studies have shown that thrombolytic therapy (streptokinase) for complicated parapneumonic effusions have been effective if administered early and at this stage show a 70-90% success rate in halting the progression to empyema
- VATS – videa assisted throrascopy, with the patient under local or general anesthesia to allow direct visiulisation, via an endoscope so minimally invasive, of the empyema so it can be drained completely or decortication = removal of inflamed pleural layer. Most often used in patients with multi-located empyema
