Types
of infection
A
wound abscess presents all the Celsian clinical features of acute inflammation: calor
(heat), rubor (redness), dolor (pain)and tumour(swelling),to
which can be added functio
leasa (loss of function )
Abscesses
may need débridement and curettage with an exploration to break down all loculi
before resolution can occur. Persistent chronic abscesses may lead to sinus or
fistula formation. In a chronic abscess, lymphocytes and plasma cells are seen
with sequestration and later calcification. Certain organisms are related to
chronicity, sinus and fistuba formation, e.g. mycobacteria and actinomyces, and
should not be forgotten.
Perianastomotic
abscesses may be the cause or result of anastomotic leakage. Deep cavity abscess
(pleura or peritoneum) may be difficult to diagnose or locate even when there is
strong clinical suspicion (Fig. 7.6). Plain or contrast radiographs may not be
helpful, whereas ubtrasonography,
The
role of antibiotics in the treatment of wound abscesses is controversial unless
there are signs of spreading infection (ceblulitis or lymphangitis). Surgical
decompression and curettage must be adequate and may allow resuture without
antibiotics but this is also controversial. Delayed primary or secondary suture
is safer.
This
is the nonsuppurative invasive infection of tissues. In addition to the cardinal
signs of inflammation, there is poor bocabisation. Spreading infection is
typical of organisms such as f3-haemolytic streptococci (Fig.
7.7),
staphylococci (Fig. 7.8) and C. perfringens. Tissue destruction and
ulceration may follow, caused by release of streptokinase, hyaburonidase and
other proteases.
Systemic
signs (toxaemia) are common: SIRS, chills, fever and rigors. These follow
release of exotoxins and cytokines but blood cultures are often negative.
Lymphangitis
is caused by similar processes but presents as painful red streaks in affected
lymphatics. Cellulitis is usually located at the point of injury and subsequent
tissue infection. Lymphangitis is often accompanied by painful lymph node groups
in the rebated drainage area.
Bacteraemia
and septicaemia
These
are unusual in superficial wound infections but common after anastomotic
breakdown. They are usually transient and follow procedures undertaken through
infected tissues (particularly instrumentation in infected bile or urine).
Specific
wound infections
Gas
gangrene is caused by C. perfringens. The Gram-positive, spore-bearing
bacilli are widely found in nature, particularly soil and faeces, which is
relevant to military and traumatic surgery, and colorectab operations. Patients
who are immunocompromised, diabetic or
have malignant disease are at risk, particularly when anaerobic wound conditions
are present with necrotic or foreign material. Wound infections are associated
with severe local wound pain and crepitus (gas in the tissues which may also be
noted on plain radiographs). The wound presents a thin, brown, sweet-smelling
exudate, from which bacteria can be recognised on Gram staining. Oedema and
spreading gangrene follow the release of collagenase, hyaburonidase, other
proteases and a-toxin. Systemic complications with circulatory collapse and MSOF
supersede without appropriate intervention.
Prophylaxis
in patients at risk should always be considered, particularly amputation for
peripheral vascular disease. Once established, barge doses of intravenous
penicillin and aggressive débridement of affected tissues are required. The
use of hyperbaric oxygen is controversial.
Synergistic
spreading gangrene (necrotising fasciitis) is not caused by cbostridia. A mixed
pattern of organisms is responsible — cobiforms, staphylococci, Bacteroides
spp., anaerobic streptococci and pepto-streptococci have been implicated.
Synonyms have been associated with abdominal wall infections (Meleney’s
synergistic hospital gangrene) and scrotal infection (Fournier’s gangrene,
Fig. 7.9). Patients are almost always immunocompromised (such as diabetes
mebbitus). The initial wound may have been minor, but severely