Surgical Infections

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).

⭐ 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.

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.

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.