Aspiration and chemotherapy
If the presence of a pleural effusion
is recognized early, if aspiration produces fluid from which the solid deposit
on standing is less than one-third of the total volume, and if the bacteria are
sensitive to some antibiotic suitable for intra-pleural injection, there is a reasonable chance that
the empyema will be quickly and completely cured by repeated aspiration
combined with local chemotherapy. Aspiration must be repeated as often as the
fluid re-collects, so that the pleural cavity is kept constantly as dry as
possible. At the beginning of treatment this may entail aspiration on alternate
days or even daily. At the end of each aspiration the appropriate antibiotic is
injected into the empyema, and this should not be omitted until it is found
impossible to demonstrate bacteria in a film of the pus on at least two
consecutive occasions. It is more satisfactory to rely on microscopic
examination of the pus than on cultures, for bacteria may be present and yet
fail to grow when incubated on suitable media. In the case of
penicillin-sensitive bacteria, it is suggested above that the initial dose
should be in the region of 500,000 units, but, subsequently, it is doubtful
whether anything is gained by exceeding 100,000 units at each intrapleural
injection.
It cannot be over-emphasized that treatment solely by
aspiration and local chemotherapy is justified only when the infected pleural
effusion is recognized early, and it should not be continued unless the fluid
becomes progressively thinner and ceases to re-accumulate within 2-3
weeks. There is a great tendency to misapply this form of therapy in order to avoid an
operation ; thus, it is not uncommon to find a well-localized empyema
containing thick (although sterile) pus being treated for weeks on end by
aspiration and local chemotherapy. If this is done, there is a serious risk
that the patient will be left with a chronic cavity containing sterile pus, but
this pus may become reinfected at any time. Even if the cavity is finally
obliterated, the functional result is certain to be poor, as the result of the
formation of much scar tissue which limits respiratory movement. In special
circumstances—for
example, in frail senile patients or when the empyema follows a palliative
operation for cancer—it may be justifiable to ignore the probability of an
imperfect result, but the risks should be fully appreciated. Children under the
age of 3 years have a remarkable capacity to absorb inflammatory exudates, so
that an empyema which contains quite thick pus may clear up entirely following
repeated aspiration and intrapleural chemotherapy (Fig. 10); but, even with
these small children, there should be no hesitation in abandoning this line of
treatment if the lung does not rapidly expand and obliterate the empyema
cavity.
Rib
resection and external drainage in localized empyema
Most cases of empyema require rib resection and
external drainage as soon as the pus has become localized by adhesions. The
dangers of operating before the empyema has become localized are now well
recognized. It is obvious that, if there are no adhesions between the two
pleural surfaces, exposure of the pleural cavity to atmospheric pressure will
cause almost total collapse of the lung and a shift of the mediastinum towards
the opposite side. In addition, the mediastinum will be drawn further towards the
" good " side on each inspiration, but will return to its former
position on expiration. This to-and-fro movement of the mediastinum, or
"mediastinal flutter", not only decreases the ventilation of the
" good " lung but also embarrasses the circulation. Furthermore, the
gas inspired into the " good " lung may not have the normal
respiratory value, for the air drawn down the trachea is likely to be mixed
with gas drawn from the partially collapsed lung, and this gas will contain
less oxygen and more carbon dioxide than does atmospheric air. These
deleterious effects, which are common to all forms of open pneumothorax in the
absence of pleural adhesions, will be aggravated if the pneumonic process is
still active. If the communication with the atmosphere is maintained by means
of a tube, the embarrassment to respiration is likely to increase progressively
and lead to the death of the patient. This sequence of events was responsible
for the extremely high mortality in cases submitted to premature drainage at the
end of World War I.
Various methods of treating a septic pleural effusion
before it has become localized have been tried, but there is little doubt that
the most satisfactory technique is repeated aspiration combined with local
chemotherapy, in the same manner as that described above for early cases, in
which this mode of treatment is adopted in an attempt to abort the condition.
With such therapy, the empyema is likely to become localized in a very short
time and the patient's general condition to improve rapidly, particularly in
those cases in which the pus becomes sterile as a result of the local
chemotherapy.
In the past, evidence that the empyema had become
localized was derived
almost entirely from the character of the pus. When
the pus was thick, so that, on standing, the solid deposit exceeded half the
total volume, the empyema was presumed to have become localized by adhesions.
This was a fair assumption and still applies to-day. A sample of pus should
therefore be taken at the time of each aspiration and placed in a rack in the
ward, so that the amount of deposit on standing may be seen at a glance. If
local chemotherapy is used, however, the pus may not become increasingly thick,
although the empyema has in fact become localized. Consequently, evidence that
the empyema has become localized should be sought not only from the character
of the pus but also from the radiological appearances. If skiagrams show a
well-defined shadow restricted to one part of the chest, it is likely that the
pleural fluid has become confined by adhesions. In cases of doubt a small
quantity of air, but not more than 10 millilitres, may be injected into the
empyema, skiagrams being subsequently taken in the upright position, in order
to determine whether this air is free to rise to the apex of the pleural cavity
or whether, on the other hand, it is restricted to a limited empyema cavity
(Fig. 11).
All localized empyemas should be drained by rib
resection, even if the pus is sterile and the patient apparently free from
toxaemia. Before doing so, 5 millilitres of iodized oil are injected into the
cavity and frontal and lateral skiagrams taken, using increased penetration.
The oil falls to the bottom of the empyema, and it is therefore possible to
determine from the skiagrams the exact site at which a portion of rib must be
resected in order to furnish dependent drainage (Fig. 11). Some surgeons
recommend that drainage should never be provided lower than the tenth rib in
the scapular line or the ninth rib in the posterior axillary line, even if the
oil falls below this level, because it is claimed that drainage is hkely to be
hindered by a rise in the position of the diaphragm following operation. It is
certainly uncommon for the oil to drop below the levels mentioned, but, when it
does do so, there should be no hesitation in resecting a portion of rib at the
level demonstrated as the bottom of the cavity, for the tube can always be
lengthened after operation if the diaphragm rises.
Technique
of rib resection and external drainage
The operation is performed under local anaesthesia
with the patient lying in that position which provides the surgeon with the
most easy access to the site selected for drainage. For resection of a rib
posteriorly or in the axilla, the patient lies on the "good" side,
buttressed by a large support placed anteriorly. An operation should never be
performed until the patient is fit enough to lie comfortably in this position for
as long as is required. This does not apply to cases complicated by a
broncho-pleural fistula, because operation must then be performed with the
patient firmly supported in the sitting position, for recum-bency is likely to
cause the pus to enter the bronchial tree through the fistula and thus promote
incessant coughing or even drown the patient.
An incision 3-4 inches long is made over the portion
of rib selected for resection, and the superficial muscles are divided so as to
expose the rib. If the resection is to be made close to the midline
posteriorly, a vertical incision along the lateral border of the sacrospinalis
muscle provides the best exposure ; in all other cases, the incision is
preferably made in the line of the rib, although some surgeons
recommend a vertical incision for all cases. At least
3 inches of the rib should be resected subperiosteally. A needle is then passed
through the rib bed, in order to confirm that the site chosen for operation
does in fact overlie the empyema. As soon as pus is obtained, a small incision
is made through the rib bed so that the pus may escape slowly. When the flow of
pus diminishes, the opening into the empyema is extended for the full length of
the portion of rib resected. The rest of the pus is subsequently removed by
suction and all fibrinous masses are extracted by means of sponge-holding
forceps. The empyema is then inspected with the aid of a light suitable for
introduction into the cavity ; the light on the end of a cystoscope will serve
this purpose if there is no special instrument available. Any fibrin adhering
to the parietes or lung surface should be gently wiped away and extracted. The
mobility of the lung may be ascertained by getting the patient to cough gently.
If the empyema has not been entered at its lowest limit, a further portion of
the same rib or a segment of another rib must be resected, so that the cavity
may be drained from the bottom. A large rubber tube—at least \ inch in internal diameter for an
adult—is inserted so that the inner end projects about I inch inside the
cavity. Finally the superficial muscles and skin are sutured around the
drainage tube. This tube is held in position by transfixing it on a level with
the skin with a safety-pin, which is anchored to the chest by long pieces of
adhesive strapping. The dressings are applied around the tube and held in
position with gate strapping. Bandages or strapping which encircle the chest
should be avoided because they restrict respiratory movement. Unless the
empyema is very small, the drainage tube should be connected to a water-seal
bottle, in order that the patient may develop a moderate negative pressure
within the empyema and so encourage re-expansion of the lung. Water-seal
drainage also provides for the discharge to be carried away from the dressings
(Fig. 12).
Drainage
by an intercostal tube—disadvantages
In this discussion on treatment, the use of
intercostal-tube drainage has not been mentioned. Such drainage should never be
employed for an adult in the treatment of a localized empyema, because the
introduction of the tube does not provide an opportunity to remove fibrin and
the calibre of the tube is necessarily too small to provide efficient drainage.
Furthermore, an intercostal tube often becomes painful after a week or so,
because of irritation of the intercostal nerve, and it sometimes causes
pressure necrosis of part of one of the adjacent ribs. However, some clinicians
maintain that, prior to localization of an empyema, the use of an intercostal
tube connected to a water-seal bottle is preferable to repeated aspiration.
Before the introduction of effective local chemotherapy, it could be argued
that continuous drainage through an intercostal tube was better than
intermittent aspiration, particularly in those cases of streptococcal effusion
which re-collected very rapidly. But, with the use of antibiotics, it is rare
to see an effusion re-collect quickly, and most empyemas soon become localized
and ready for drainage by rib resection. It is therefore doubtful whether there
is now any place for intercostal drainage in the treatment of empyema. If it is
employed it should always be followed by rib resection, although an exception
to this rule may sometimes be made in the case of small children.
