7.5 Recognizing Complications, Infection Signs, & When to Seek Care

Recognizing Complications, Infection Signs, & When to Seek Care

Wound infection represents a continuum that ranges from superficial bacterial colonization to deep soft-tissue invasion, osteomyelitis, and life-threatening systemic sepsis. Because patients with diabetes, peripheral arterial disease, or immunosuppression often exhibit blunted inflammatory responses, classic infection signs may be subtle or absent. Clinicians must equip patients, family caregivers, and home health staff with standardized diagnostic frameworks—specifically the NERDS and STONEE criteria—to identify local versus deep infection early, establishing clear protocols for immediate emergency medical escalation.

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The Wound Infection Continuum

Microbial burden on the wound surface progresses through five distinct stages:

1. Contamination: Non-replicating bacteria present on the wound surface; no host tissue reaction.
2. Colonization: Replicating bacteria present without host tissue damage or clinical infection.
3. Local Infection (Covert / Overt): Microorganisms proliferate within the superficial wound bed, triggering a localized inflammatory response, biofilm formation, and stalled healing.
4. Spreading Infection: Microorganisms invade deep soft tissues beyond the wound border, causing cellulitis, lymphangitis, or deep abscess.
5. Systemic Infection (Sepsis): Pathogens or toxic bacterial products enter the bloodstream, triggering Systemic Inflammatory Response Syndrome (SIRS), multi-organ failure, and septic shock.

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Diagnostic Frameworks: NERDS vs. STONEE

To guide targeted therapy, clinical infection signs are categorized into superficial/local infection (NERDS) versus deep/spreading infection (STONEE).

NERDS Criteria (Superficial / Local Infection - High Biofilm Burden)

When 3 or more of the following criteria are present, localized superficial infection is diagnosed:

• Non-healing wound: Progress has stalled for > 2 weeks despite appropriate off-loading or dressing management.
• Exudate increase: Sudden escalation in drainage volume or change to purulent consistency.
• Red and bleeding friable tissue: Granulation tissue appears dark red, dull, exuberant, and bleeds easily upon gentle contact.
• Debris / Slough: Rapid accumulation of yellow/gray necrotic slough or stringy exudate within the wound bed.
• Smell / Malodor: New onset of foul odor upon dressing removal.
• Clinical Management: Treated primarily with topical antimicrobial dressings (e.g., medical-grade silver, cadexomer iodine, honey) and aggressive biofilm-disrupting wound bed debridement. Systemic antibiotics are generally not indicated for localized NERDS infection.

STONEE Criteria (Deep / Spreading Tissue Infection)

When 3 or more of the following criteria are present, deep invasive infection is diagnosed:

• Size increasing: Wound dimensions (length, width, or depth) enlarge despite treatment.
• Temperature elevated: Periwound skin temperature increases by >= 1.1 to 2.2°C (2 to 4°F) compared to surrounding normal skin.
• Osteomyelitis / Probe-to-bone: Metallic probe easily contacts hard, gritty bone at the wound base, or bone is visually exposed.
• New areas of breakdown: Satellite ulcers, tissue sinus tracts, or bullae form in periwound skin.
• Erythema extending > 2 cm beyond the wound border.
• Exudate / Edema / Induration: Spreading tissue edema and firm induration extending into surrounding structures.
• Clinical Management: Mandates systemic oral or intravenous broad-spectrum antibiotics, urgent imaging (x-rays, MRI), surgical consult for deep space debridement, and wound cultures.

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Systemic Infection Red Flags & SIRS Criteria

Systemic infection represents a medical emergency. Clinicians, patients, and caregivers must monitor for systemic toxicity indicators:

Systemic Inflammatory Response Syndrome (SIRS) Parameters

Systemic sepsis is defined by the presence of 2 or more of the following clinical criteria in the setting of a wound infection:

1. Core Body Temperature: > 38.0°C (100.4°F) OR < 36.0°C (96.8°F) (hypothermia indicates severe septic shock).
2. Heart Rate: > 90 beats per minute (tachycardia).
3. Respiratory Rate: > 20 breaths per minute (tachypnea) or PaCO2 < 32 mmHg.
4. Leukocyte Count (WBC): > 12,000/µL, < 4,000/µL, or > 10% immature band forms.

Unexplained Hyperglycemia in Diabetes

In diabetic patients, a sudden, unexplained elevation in blood glucose (> 200 mg/dL or > 11.1 mmol/L) despite compliance with insulin/medication regimens is frequently the earliest indicator of deep tissue infection, occurring 24 to 48 hours before clinical fever or spreading redness appears due to stress-induced cortisol and inflammatory cytokine release.

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Emergency Red Flags & Immediate Escalation Protocol

Patients and caregivers must receive a written card detailing explicit "Red Flag" symptoms that require immediate transfer to an Emergency Department (ED):

1. Rapidly Spreading Cellulitis: Periwound redness expanding > 2 cm within a 24-hour period, or red streaks ascending the limb (lymphangitis).
2. Subcutaneous Crepitus: A crackling, bubbling sensation felt under the skin upon gentle palpation, signifying subcutaneous gas produced by anaerobic gas-forming organisms (e.g., Clostridium perfringens, polymicrobial necrotizing fasciitis).
3. Tissue Necrosis & Gangrene: Blackening of skin (eschar formation), purple discoloration, fluid-filled bullae, or sudden loss of sensation in a previously painful wound.
4. Severe Unrelieved Ischemic Pain: Excruciating, sudden lower extremity pain unalleviated by elevation or analgesics, signaling acute arterial thrombosis or compartment syndrome.
5. Systemic Collapse: Confusion, severe lethargy, rigors/chills, diaphoresis, or systemic hypotension (systolic BP < 90 mmHg).