10.1

Infections

Chapter 10

Infections

Introduction

All wounds incurred on the battlefield are grossly

contaminated with bacteria. Most will become infected

unless appropriate treatment is initiated quickly.

The battlefield environment is conducive to wound infection

due to

 Absence of “sterile” wounding agents on the battlefield. All

foreign bodies (wounding projectile fragments, clothing, dirt)

are contaminated with bacteria.

 High-energy projectile wounding (devitalized tissue,

hematoma, tissue ischemia).

 Delay in casualty evacuation.

Diagnosis of a Wound Infection

 The four “-ors:” dolor, rubor, calor, and tumor—pain and

tenderness, redness, warmth, and swelling.

 Drainage or discharge, ranging from frank pus to the foul

“dishwater” discharge of clostridial infection.

 Crepitus, radiographic evidence of soft-tissue gas, epidermal

blistering, and/or epidermal necrosis are the hallmarks of

necrotizing soft tissue infection, such as clostridial gas

gangrene or necrotizing fasciitis.

 Systemic effects such as fever, leukocytosis, unexplained

tachycardia, or hypotension.

 Confirm diagnosis by Gram stain and culture, if available,

and/or tissue biopsy.
10.2

Emergency War Surgery

Common Microorganisms Causing Battlefield Infections

 Gram-positive cocci: staphylococci, streptococci, and

enterococci.

 Gram-negative rods: Escherichia Coli, Proteus, and Klebsiella.

ο Pseudomonas, Enterobacter, Acinetobacter, and Serratia are

common nosocomial pathogens usually expected among

casualties who have been hospitalized for an extended

period, not those fresh off the battlefield.

 Salmonella, Shigella, and Vibrio should be suspected in cases

of bacterial dysentery.

 Anaerobic Gram-positive and Gram-negative rods: Clostridia,

Bacteroides, and Prevotella species.

 Fungal species: Candida species should be suspected in casualties

hospitalized for prolonged periods, those malnourished or

immunosuppressed, or those who have received broad

spectrum antibiotics, adrenocortical steroids, or parenteral

nutrition. Empiric therapy should be considered in appropriate

patients with presumptive evidence of fungal infection.

The greatest threat of infection to the wounded battlefield

casualty is the development of clostridial myonecrosis (gas

gangrene), commonly due to Clostridium perfringens.

Common Patterns of Infection

 Skin, soft tissue, muscle, and bone: Primarily due to

staphylococcal, streptococcal, and clostridial species. These

infections include wound abscess, cellulitis, septic arthritis,

osteomyelitis, necrotizing fasciitis, and gas gangrene.

Clostridium tetani can enter through any wound—even

minor burns and corneal abrasions. Prophylaxis is required

to prevent tetanus toxemia.

 Intracranial: Meningitis, encephalitis, and abscess,

commonly due to staphylococci and Gram-negative rods,

which are difficult to treat due to the impervious nature of

the meninges to common antibiotics.
10.3

Infections

 Orofacial and neck: Gram-positive cocci and mouth

anaerobes, generally responsive to surgery and clindamycin.

 Thoracic cavity: Empyema (usually staphylococcal) and

pneumonia (Staphylococcus, Streptococcus, Pseudomonas),

especially among those on prolonged mechanical ventilation

or those casualties prone to aspiration (polymicrobial).

 Intraabdominal: Include posttraumatic or post-operative

abscess, and peritonitis due to Enterococcus, Gram-negative

rods, and anaerobic bacilli. Clostridium difficile is often

responsible for a potentially severe diarrheal colitis that

occurs following the administration of even one dose of

antibiotic.

 Systemic sepsis: A syndrome caused by a bloodborne or

severe regional infection resulting in a global inflammatory

response (fever, leukocytosis, tachycardia, tachypnea, and

possibly hypotension).

ο A similar inflammatory response without infection can be

caused by a focus of retained necrotic tissue, or the mere

act of sustaining severe trauma.

ο Culprit microorganisms will not be recovered in all cases

of sepsis syndrome.

ο Although typically associated with Gram-negative

organisms, any bacterial or fungal agent can cause sepsis.

Prompt surgical debridement is the cornerstone of

prophylaxis/treatment of war wound infections.

Treatment

General Principles

 Surgical and antibiotic treatment should begin early and be

repeated in the prophylaxis of war wound infection.

 Optimally, surgical debridement should be achieved within

6 hours of injury.

 Following initial exploration and debridement, the wound

should be sufficiently irrigated to ensure all dead material,

bacterial contamination, and foreign material has been

washed from the wound.
10.4

Emergency War Surgery

 Excessive irrigation, especially under pressure, should be

avoided, because this can dilute the body’s natural immune

cellular defenses and contribute to bacteremia.

 The skin is left open, and a lightly moistened sterile gauze

dressing is applied.

 Antibiotics should be started ASAP after wounding, then

continued for 24 hours, depending on the size, extent of

destruction, and degree of contamination of the wound.

ο If time from wounding to initiation of antibiotics is > 6

hours, or time from wounding to surgery is > 12 hours,

give antibiotics using regimen for established infection.

 The choice of empiric antibiotic is dependent on the part of

the body injured (Table 10-1).

 Once a battlefield wound has become infected, treatment is

two-fold—surgical and medical.

ο Surgical strategy remains the same: Open the wound, remove

infected and necrotic tissue, and inspect for foreign material.

ο Drainage is generally employed in abscess cavities to

prevent premature closure and reformation.

ο Empiric broad-spectrum antibiotic therapy is initiated

against likely pathogens and continued for 7 to 10 days.

ο Ideally, obtain cultures and tailor therapy to cover the

actual pathogens recovered on Gram stain and culture.

Routine bacteriology is often not available in forward

medical facilities.

ο Because Bacteroides and Clostridia are difficult to culture,

tailor antibiotic therapy to cover these organisms.

ο If the debrided wound still has possibly ischemic tissue or

retained foreign material, the patient is returned to the OR

every 1 to 2 days for redebridement, until absolute

assurance of healthy, clean tissue is achieved.

Specific Infections

 Tetanus.

ο Battlefield wounds are “tetanus-prone” due to high levels

of contamination with Clostridium tetani.

ο Bacteria grow anaerobically and release a CNS toxin that

results in muscle spasm, trismus, neck rigidity, and back

arching.
10.5

Infections

Table 10-1. Empiric Antibiotic Coverage for War Injuries.

Site of Injury Empiric Antibiotic Covered Organisms

Cranium/penetrating Ancef/Vanc + Flagyl Gram positives + anaerobes

injury brain injury

Maxillofacial Ancef + clindamycin Gram positives + anaerobes

Neck Ancef Skin flora

Chest Ancef Skin flora

Abdomen

Liver Fluoroquinolone/2nd generation Gram negatives, gram positives,

cephalosporin + anaerobes

Gastrointestinal tract Carbapenam/penicillin (Zosyn) “

with gross contamination

Gastrointestinal tract 2nd generation cephalosporin “

without gross contamination

Genitourinary Aminoglycoside + 2nd generation “

cephalosporin

Spleen 2nd generation cephalosporin + “

fluoroquinolone + immunize splenectomy

patients later for encapsulated organisms

Pelvic

With gastrointestinal injury Carbepenam or combo penicillin Gut flora + anaerobes

No gastrointestinal injury 2nd generation cephalosporin Skin organisms

Extremity

Soft tissue only Ancef or 2nd generation cephalosporin

+ aminoglycoside

Bone/vascular involvement 2nd generation cephalosporin +

aminoglycoside and fluoroquinolone

Treat gross contamination of any wound with debris from uniforms and the environment with broad spectrum Gram-negative and

anaerobic coverage regardless of area of injury, eg, Ancef + penicillin + gentamicin; or Unasyn alone.
10.6

Emergency War Surgery

ο In addition to surgical debridement of war wounds,

additional prophylactic measures for tetanus-prone

wounds include

♦ Administration of 0.5ml IM of tetanus toxoid if prior

tetanus immunization is uncertain, less than three doses,

or more than five years since last dose.

♦ Administration of 250–500 units IM of tetanus immune

globulin in a separate syringe and at a separate site from

the toxoid if prior tetanus immunization is uncertain

or less than three doses.

ο Treatment for established tetanus includes

♦ IV antibiotics (penicillin G, 24 million U/d; or

doxycycline, 100 mg bid; or metronidazole, 500 mg q6h

for 7 days).

♦ Tetanus immune globulin.

♦ Wound debridement as needed.

♦ IV diazepam to ameliorate the muscle spasm.

♦ Place patient in a dark, quiet room free of extraneous

stimulation.

♦ May warrant endotracheal intubation, mechanical

ventilation, and neuromuscular blockade.

 Soft-tissue infections.

ο Cellulitis is manifested by localized skin erythema, heat,

tenderness, and swelling or induration.

♦ Treatment: IV antibiotics against streptococcal and

staphylococcal species (IV nafcillin, cefazolin or, in the

penicillin-allergic patient, clindamycin or vancomycin).

ο Post-operative wound infections become evident by

wound pain, redness, swelling, warmth, and/or foul or

purulent discharge, with fever and/or leukocytosis.

♦ Treatment: Open the wound, drain the infected fluid,

and debride any necrotic tissue present.

♦ The wound is left open and allowed to close via

secondary intention.

ο Necrotizing soft tissue infections are the most dreaded

infections resulting from battlefield wounding. These

include clostridial myonecrosis (gas gangrene) and

polymicrobial infections caused by Streptococcus,

Staphylococcus, Enterococcus, Enterobacteriaceae, Bacteroides,

and Clostridia.
10.7

Infections

♦ The organisms create a rapidly advancing infection

within the subcutaneous tissues and/or muscle by

producing exotoxins that lead to bacteremia, toxemia,

and septic shock.

♦ All layers of soft tissue can be involved, including skin

(blistering and necrosis), subcutaneous tissue

(panniculitis), fascia (fasciitis), and muscle.

♦ Clinical manifestations begin locally with severe pain,

crepitus, and with clostridia, a thin, brown, foulsmelling discharge.

♦ The skin may be tense and shiny, showing pallor or a

bronze color.

♦ Systemic signs include fever, leukocytosis, mental

obtundation, hemolytic anemia, and hypotension,

progressing rapidly to multiple organ failure and death

in untreated or under-treated cases.

♦ The diagnosis is made by history of severe unexpected

wound pain combined with palpable or radiographic

soft tissue gas (air in subcutaneous tissue and/or

muscle).

♦ Absence of soft-tissue gas does not exclude diagnosis

of necrotizing infection.

♦ Treatment is surgical, including early, comprehensive,

and repeated (every 24–48 hours) debridement of all

dead and infected tissue, combined with antibiotics.

♦ Excision of affected tissue must be as radical as

necessary (including amputation or disarticulation) to

remove all muscle that is discolored, noncontractile,

nonbleeding, or suspicious.

♦ Identification of causative organisms often problematic:

Treatment must be aimed at all possible organisms.

♦ IV antibiotic therapy.

♦ Clindamycin, 900 mg q8h; plus penicillin G, 4 million

U q4; plus gentamicin, 5–7 mg/kg qd.

◊ As a substitute for clindamycin: metronidazole, 500

mg q6h.

◊ As a substitute for penicillin: ceftriaxone, 2.0 g q12h,

or erythromycin 1.0 g q6h.

◊ As a substitute for gentamicin: ciprofloxacin, 400 mg

q12h.
10.8

Emergency War Surgery

♦ Alternative regimen: penicillin G, 4 million U q4h plus

imipenem, 500 mg q6h.

 Intraabdominal infections.

♦ Prevention.

♦ Regimens (start ASAP, continue x 24 hours post-op).

◊ Single agent: cefotetan 1.0 g q12h, or ampicillin/

sulbactam, 3 g q6h, or cefoxitin, 1.0 g q8h.

◊ Triple agent: ampicillin 2 g q6h; plus anaerobic coverage

(metronidazole, 500 mg q6h; or clindamycin, 900 mg

q8h); plus gentamicin 5–7 mg/kg qd.

♦ Established intraabdominal infection (peritonitis or

abscess).

♦ Same regimen as above, except continue for 7 to 10 days.

♦ Drain all abscesses.

 Pulmonary infections.

♦ Empyema (generally Streptococcal) following penetrating

thoracic trauma is typically due to contamination from

the projectile, chest tubes, or thoracotomy.

♦ Diagnosis: Loculations, air/fluid levels on radiograph,

pleural aspirate.

♦ Treatment.

◊ Chest tube initially, and thoracotomy if unsuccessful.

◊ Cefotaxime, or ceftriaxone, or cefoxitin, or imipenem.

♦ Pneumonia is most frequently due to aspiration (eg,

patients with head injury) and prolonged mechanical

ventilation.

♦ The diagnosis is made through radiograph finding of a

new pulmonary infiltrate that does not clear with chest

physiotherapy, combined with

◊ Fever or leukocytosis.

◊ Sputum analysis showing copious bacteria and

leukocytes.

♦ Empiric therapy is directed toward likely pathogens.

◊ Aspiration: Streptococcal pneumonia, coliforms, and

oral anaerobes are likely. IV antibiotics such as

ampicillin/sulbactam, clindamycin, or cefoxitin have

proven effective.

◊ Ventilator-associated pneumonia: staphylococcus,

Pseudomonas, and other nosocomial Enterobacteriaceae.

Broad coverage is best with such agents as imipenem,
10.9

Infections

ciprofloxacin, vancomycin, and/or ceftazidime, plus

an aminoglycoside.

Systemic Sepsis

Sepsis can be defined as infection combined with a prolonged

systemic inflammatory response that includes two or more of

the following conditions.

 Tachycardia.

 Fever or hypothermia.

 Tachypnea or hyperventilation.

 Leukocytosis or acute leukopenia.

Progression to septic shock is manifest by systemic

hypoperfusion: profound hypotension, mental obtundation, or

lactic acidosis. Treatment is a three-pronged approach:

 Identify and eradicate the source.

 Broad-spectrum intravenous antibiotics for the most likely

pathogens.

 ICU support for failing organ systems, such as cardiovascular

collapse, acute renal failure, and respiratory failure.

It is often difficult to identify the source of sepsis, but it is the

most important factor in determining the outcome. Potential

sources of occult infection include

 An undrained collection of pus such as a wound infection,

intraabdominal abscess, sinusitis, or perianal abscess.

 Ventilator-associated pneumonia.

 Urinary tract infection.

 Disseminated fungal infection.

 Central intravenous catheter infection.

 Acalculous cholecystitis.

Intensive care support for sepsis involves vigorous resuscitation

to restore perfusion to prevent multiple organ dysfunction.

This requires optimization of hemodynamic parameters

(pulmonary artery occlusion pressure, cardiac output, and

oxygen delivery) to reverse anaerobic metabolism and lactic

acidosis. Endpoints of resuscitation, such as urine output,

base deficit, and blood lactate levels guide successful

treatment. Until the source for sepsis is identified and actual

pathogens isolated, empiric therapy with broad-spectrum

intravenous antibiotics is warranted. Suitable regimens might

include
10.10

Emergency War Surgery

 Imipenem, 500 mg q6h.

 Piperacillin and tazobactam (Zosyn), 3.375 g q6h; or

ceftazidime, 2.0 g q8h; or cefepime, 2.0 g q12h; PLUS

gentamicin, 5–7 mg/kg qd (based on once-daily dosing

strategy and no renal impairment); or ciprofloxacin, 400 mg

q12h.

 Addition of vancomycin, 1.0 g q12h if methicillin-resistant

Staphylococcus aureus is a likely pathogen.

 Addition of linezolid, 600 mg q12h if vancomycin-resistant

enterococcus (VRE) is a likely pathogen.

Conclusion

Battlefield casualties are at high risk for infection. In particular,

war wounds are predisposed to infection due to environmental

conditions on the battlefield, devitalized tissue, and foreign

bodies in the wound. The key to avoiding wound infection is

prompt and adequate wound exploration, removal of all foreign

material, and excision of all dead tissue. All battlefield wounds

and incisions should have the skin left open. Antibiotics play

an adjunctive role in the prophylaxis of wound and other

infections in the battlefield MTF. Knowledge of likely pathogens

for particular infections and sites, as well as optimal antibiotics

to eradicate those pathogens (Table 10-2), will aid the battlefield

clinician in averting and treating infections.
10.11

Infections

Agent Antibacterial Spectrum Dosage

Penicillin G Streptococcus pyogenes, penicillin-sensitive Streptococcus pneumonia, 4 mil U IV q4h

clostridial sp

Ampicillin Enterococcal sp, streptococcal sp, Proteus, some E coli, Klebsiella 2 g IV q6h

Ampicillin/ Enterococcal sp, streptococcal sp, Staphylococcus,* E coli, 3 g IV q6h

sulbactam Proteus, Klebsiella, Clostridial sp, Bacteroides/Prevotella sp

Nafcillin Staphylococcal sp,* streptococcal sp 1 g IV q4h

Piperacillin/ Enterococcal sp, streptococcal sp, Staphylococcus,* E coli, Pseudomonas 3.375 g IV q6h

tazobactam and other enterobacteriaceae, clostridial sp, Bacteroides/Prevotella sp

Imipenem Enterococcal sp, streptococcal sp, Staphylococcus,* E coli, Pseudomonas 500 mg IV q6h

and other enterobacteriaceae, clostridial sp, Bacteroides/Prevotella sp

Cefazolin Staphylococcal sp,* streptococcal sp, E coli, Klebsiella, Proteus 1.0 g IV q8h

Cefoxitin Staphylococcal sp,* streptococcal sp, E coli and similar enterobacteriaceae, 1.0 g IV q6h

clostridial sp, Bacteroides/Prevotella sp

Ceftazidime Streptococcal sp, E coli, Pseudomonas and other enterobacteriaceae 2.0 g q8h

Ceftriaxone Streptococcal sp, staphylococcal sp,* Neisseria sp, E coli and most 2.0 g q12h

enterobacteriaceae (NOT Pseudomonas), clostridial sp

Ciprofloxacin E coli, Pseudomonas and other enterobacteriaceae 400 mg q12h

Gentamycin E coli, Pseudomonas and other enterobacteriaceae 5–7 mg/kg qd (based on oncedaily dosing strategy and no

renal impairment)

Vancomycin Streptococcal, enterococcal, and staphylococcal species (including MRSA; 1.0 g q12h

not VRE)

Erythromycin Streptococcal sp, clostridial sp 0.5–1.0 g q6h

Clindamycin Streptococcus sp, Staphylococcus sp,* clostridial sp, Bacteroides, and Prevotella sp 900 mg q8h

Metronidazole Clostridial sp, Bacteroides and Prevotella sp 500 mg q6h

*Not methicillin resistant Staphylococcus aureaus (MRSA)

 Dosage and dosage intervals are average recommendations. Individual dosing may vary.

Table 10-2. Spectrum and Dosage of Selected Antibiotic Agents.
10.12

Emergency War Surgery