Surgical Infections

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SSI Classification & Pathogens - Bug's Life in Wounds

SSIs occur at/near surgical incision within 30 days post-op, or 1 year with an implant.

  • CDC Classification:
    • Superficial Incisional SSI:
      • Involves skin & subcutaneous tissue only.
      • Criteria: Pus, positive culture, or surgeon's diagnosis.
      • Pathogens: S. aureus (most common), CoNS, Streptococcus spp.
    • Deep Incisional SSI:
      • Involves deep soft tissues (fascia, muscle layers).
      • Criteria: Purulent drainage, dehiscence with fever/pain, abscess, or surgeon's diagnosis.
      • Pathogens: S. aureus, Gram-negative bacilli (GNB e.g., E. coli), anaerobes.
    • Organ/Space SSI:
      • Involves any organ/space (excluding incision sites) manipulated during surgery.
      • Criteria: Drain pus, positive culture from aspirate, abscess, or surgeon's diagnosis.
      • Pathogens: Site-specific (e.g., E. coli, Enterococcus for intra-abdominal).

SSI Classification by Depth

Staphylococcus aureus is the leading cause of SSIs, especially for incisional types (superficial and deep).

SSI Risk & Prevention - Dodging Infection Darts

  • Patient Factors: Age, DM (>7% HbA1c), obesity (>30 BMI), smoke, poor nutrition, IC, MRSA.

  • Procedure Factors: Long duration, emergency, implant, poor technique, contamination.

  • Wound Classification & Prophylaxis Strategy:

  • Key Prevention:

    • Pre-op: Optimize patient, clip hair (NO shave), CHG-alcohol skin prep.
    • Intra-op: Asepsis, gentle handling, normothermia/glycemia.

⭐ Endogenous flora (e.g., S. aureus) = main SSI source.

SSI Diagnosis & Management - Germ Warfare Tactics

Diagnosis:

  • Clinical Signs:
    • Local: Redness, warmth, swelling, pain, purulent discharge (📌 PUS: Purulence, Undermining, Systemic signs).
    • Systemic: Fever >$ extbf{38}$°C, tachycardia >$ extbf{90}$ bpm, ↑WBC >$ extbf{12,000}$/mm³, SIRS.
  • Investigations:
    • Wound C&S (before Abx). Gram stain aids early choice.
    • Blood cultures (if systemic signs/SIRS).
    • Imaging (USS/CT) for deep/organ space SSI, abscesses.

Management:

  • Source Control (KEY):
    • I&D of collections/abscesses.
    • Debridement (necrotic tissue).
    • Wound lavage. (NPWT if complex).
  • Antibiotics:
    • Empiric (broad: S. aureus, Strep, GNBs, anaerobes).
    • Tailor to C&S; shortest effective duration.
  • Supportive: Analgesia, fluids, nutrition, glucose control.

⭐ Most common SSI pathogen: Staphylococcus aureus.

Surgical site infections with pus and wound dehiscence

Key Surgical Infections - Nasty Invaders Showdown

  • Necrotizing Soft Tissue Infections (NSTI):
    • Rapid spread, pain out of proportion, crepitus, skin necrosis. LRINEC score ≥6 (e.g. CRP >150 mg/L, WBC >15x10⁹/L).
    • Tx: Urgent surgical debridement, broad-spectrum Abx.
  • Gas Gangrene (Clostridial Myonecrosis):
    • C. perfringens. Sudden pain, crepitus, bronze skin, foul discharge. Gram +ve rods.
    • Tx: Debridement, Penicillin G + Clindamycin, ± Hyperbaric Oxygen (HBO).

    C. perfringens alpha-toxin (lecithinase) causes massive hemolysis & tissue necrosis.

  • Tetanus:
    • C. tetani. Trismus (lockjaw), risus sardonicus, opisthotonus, spasms.
    • Tx: HTIG (3000-6000 IU), Metronidazole, debridement, spasm control. 📌 SAD ANT (mgt).
  • Carbuncle:
    • S. aureus. Deep infection of multiple hair follicles (nape of neck common).
    • Tx: Incision & Drainage (I&D) if fluctuant, antibiotics. Necrotizing Fasciitis: Stages and Management

High‑Yield Points - ⚡ Biggest Takeaways

  • Staphylococcus aureus is the most common organism for Surgical Site Infections (SSI).
  • Administer prophylactic antibiotics within 1 hour before surgical incision.
  • Clean-contaminated wounds carry a higher infection risk than clean wounds.
  • Necrotizing fasciitis is a surgical emergency requiring prompt, aggressive debridement.
  • Gas gangrene, caused by Clostridium perfringens, presents with crepitus and systemic toxicity.
  • Early postoperative fever (within 48 hours) is often due to atelectasis, not necessarily infection.
  • Source control (e.g., drainage, debridement) is crucial in managing established surgical infections.

Practice Questions: Surgical Infections

Test your understanding with these related questions

In a surgical post-op ward, a patient developed wound infection. Subsequently 3 other patients developed similar infections in the ward. What is the most effective way of preventing the spread of infection?

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Flashcards: Surgical Infections

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Sutures can act as foreign body after the initial _____ days

TAP TO REVEAL ANSWER

Sutures can act as foreign body after the initial _____ days

7-8

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