Empyema

00:01 Empyema also develops independent of pneumonia.

00:05 So for example, there are patients who present with just pleural infection with primary community-acquired pleural infection where the pleura has been affected directly. The root of their infection is not clear but there is no associated pneumonia. And of course, hospital acquired infection can also cause empyema, and that might be due to pleural procedures or surgery where you get direct introduction of the bacteria during the procedure of the surgery, or it might be a consequence of hospital-acquired pneumonia as an analogous situation to what happens in the para pneumonic effusions and community-acquired pneumonia. And all these situations can lead to somebody with frank pus in the pleural space and empyema.

00:45 So, how do you identify somebody who may have pleural infection? It’s very simple. If you have evidence infection, a pyrexia, a raised C-reactive protein and evidence of the pleural effusion, you need to think that the patient may have a bacterial infection of the pleural space. The classic blood results you get in somebody who’s had an empyema for two or three weeks or a pleural infection for two or three weeks, there’s a raised C-reactive protein, a low albumin, low haemoglobin, and a raised platelet count. These are sort of inflammatory effects of the ongoing infection in the pleural space.

01:26 If you have somebody who you suspect may have pleural infection, you must do a pleural tap, the main differential diagnoses for simple parapneumonic effusions and tuberculosis for this situation. So somebody presenting with what you think is an infection of the pleural space tends out to have pneumonia of a parapneumonic effusion or it could be that they have tuberculosis of the pleural space. Those are the main differential diagnoses. But the important thing here is that if somebody presents with evidence from infection and the pleural infusion, you must do a pleural tap. When you do the pleural tap, the findings that might suggest pleural infection is it’s an exudate with raised albumin levels but with a low glucose. It’s confirmed as being an infected pleural fluid if either the culture or the microscopy identifies the infected bacteria. Unfortunately, there’s a relatively insensitive test or if the pH is less than 7, or if it’s visibly turbid, looks opaque white due to the high neutrophil count The other thing that is very suggestive of pleural infection is the presence of loculations. These are the adhesions between the visceral and the parietal pleura which cause divisions in the pleural space which are not normally there. Now, loculations of the pleural spaces are not easily picked up by chest X-ray. The shape of loculated fluid can be seen by the chest X-ray, as seen in this one, but the actual loculations you cannot see. Ultrasound, in contrast, is very sensitive. It can very often identify loculations well before you can see a loculated fluid on a chest-X-ray. And the other method of identifying loculated fluid is a CT scan which can easily describe patients with different patches of fluid due to loculations around the pleural space. So, how do you treat somebody with bacterial infection of the pleural space? Well, you do the diagnosis pleural tap, ultrasound, CT scan, and then the next thing to do is drain the infective fluid. We do that for two reasons. One is that if you drain your infective fluid, it’s like draining an abscess.

03:31 It makes control of the infection much easier. You’re reducing the bacterial load. The other is that the long-term consequence of empyema and pleural infection is that you get pleural thickening. And the less pleural fluid there is left in the patient, the less pleural thickening you’ll end up with. So, you do drains that will be inserted, usually under ultrasound guidance, but the main problem with all of these loculations and the thick fluid you’re getting in empyema makes drainage of the fluid much more complicated because the loculations will prevent drainage occur from different locules around the pleural space. For that reason, some people have used intrapleural fibrinolytics in the past, and those may be beneficial in increasing the drainage of pleural fluid, although the controlled trial data are not clear-cut or present. The ultimate way of removing fluid which is difficult to drain if somebody has a complex pleural infection is by surgery. And in fact, quite a lot of patients with empyema, with baterial infection of the pleural space, maybe a third of them will require some from a surgical intervention to clear out that pleural space properly. Bacterial infection of the pleural space is complicated because it means the patient requires prolonged treatment of antibiotics. And the antibiotics they require depends on the source of the bacterial infection. So for example, community acquired empyema, either due to primary empyema or due to associated community-acquired pneumonia. There are normally streptococci and anaerobes that are the main bacteria causing infection. Other patient can be treated with coamoxiclav or clindamycin. If it’s a hospital-acquired empyema, then more difficult organisms such as Staphylococcus aureus including MRSA and the resistant grand negative organism such as Pseudomonas become a problem, and they will require much more complex regimens of antibiotics to control the infection.

05:22 Overall, pleural infection actually is not a good disease to have. If you’re over 65 years of age, there’s a significant mortality about 30% over the hospital stay. And the hospital stay itself, if somebody comes in the hospital with pneumonia, the normal duration of that hospital stay is only a few days. If they have pleural infection, it increases to 17 days at least. As I already mentioned, the antibiotic treatment is about four to six weeks length in duration. The patient will need pleural drains and a significant number will require pleural surgery. So, developing a pleural infection is a major, major problem for the morbidity and mortality.