mortality increases as the histologic staging increases from IA to IIC with a marked increase in
mortality between stages IC and IIA and a further increase with stages IIB and IIC.
Microvascular involvement connotes the likelihood of systemic spread and the development of
burn wound sepsis, i.e., an invasive burn wound infection associated with systemic sepsis and
progressive organ dysfunction.
A negative biopsy in association with progressive clinical deterioration mandates repeat
biopsy from other areas of the wound showing changes indicative of infection. Successive
biopsies that show progressive penetration and proliferation of microorganisms within the
eschar indicate the need for a change in topical agent, i.e., institution of mafenide acetate that
can diffuse into the eschar and limit proliferation of the colonizing bacteria. The high mortality
associated with microvascular involvement and the recovery of positive blood cultures
emphasizes the importance of early diagnosis prior to hematogenous dissemination of the
invading microorganisms to remote tissues and organs or rapid proliferation locally with
production of toxins.
An immediate change in wound care is called for if a diagnosis of invasive burn wound
infection (stage II) is made. Systemic antimicrobial therapy in full dosage should be initiated
(amphotericin B or one of the newer agents in the case of fungal infections). The patient should
be prepared for surgery and taken to the operating theater as soon as possible to excise the
infected tissue, which in the case of invasive fungal infection may necessitate major
amputation to encompass extensive subcutaneous transfascial spread. Before excision of a
wound harboring an invasive bacterial infection, one-half of the daily dose of a broad-
spectrum penicillin (e.g., piperacillin/tazobactam) should be suspended in 150 to 1000 mL of
saline and injected by clysis into the subcutaneous tissues beneath the area of infection. A
second clysis should be performed immediately before operation if more than six hours have
elapsed from the initial clysis. The clysis therapy will prevent further proliferation of the
invading organisms and reduce the number of viable bacteria and their metabolic byproducts
disseminated by operative manipulation of the infected tissue. In the case of invasive fungal
infection, clotrimazole cream or powder should be applied to the infected area as soon as the
diagnosis is made and prior to excision.
Following excision of an area of invasive bacterial burn wound infection, the excised
wound should be dressed with 5% mafenide acetate soaks. The patient should be returned to
the operating room 24 to 48 hours later for thorough wound inspection and further excision of
residual infected tissue if necessary. That process is repeated until the infection is controlled
and no further infected tissue is evident at the time of re-examination. If the wound infection
was caused by a fungus, mafenide acetate soaks should not be used since they may promote
further fungal growth; Dakin’s soaks or a silver containing dressing should be used.
Successful treatment of patients with extensive burns involving the head and neck has
been associated with an increased occurrence of superficial staphylococcal infections in healed
and grafted wounds of the scalp and other hair-bearing areas. Those focal areas of suppuration
have been termed “burn wound impetigo,” which, if uncontrolled, can cause extensive
epidermal lysis of the healed and grafted burns. Daily cleansing and twice daily topical
application of mupirocin ointment typically controls the process and permits spontaneous
healing of the superficial ulcerations. If not controlled with mupirocin, control may be
Table 2 Histologic Staging of Microbial Status of the Burn Wound
Stage I: Colonization
A. Superficial: microorganisms present only on burn wound surface
B. Penetrating: variable depth of microbial penetration of eschar
C. Proliferating: variable level of microbial proliferation at the nonviable–viable tissue interface (subeschar
space)
Stage II: Invasion
A. Microinvasion: microorganisms present in viable tissue immediately subjacent to subeschar space
B. Deep invasion: penetration of microorganisms to variable depth and extent within viable subcutaneous
tissue
C. Microvascular involvement: microorganisms within small blood vessels and lymphatics (thrombosis of
vessels common)
Infections in Burns in Critical Care 367