What is slough in a wound?

What is Slough in a Wound?

Slough is dead, devitalized tissue that appears as a yellow, tan, or gray stringy or fibrous material on the wound surface and must be removed to promote wound healing. 1

Characteristics of Slough

• Slough is commonly found in Stage III and IV pressure injuries, where it presents as a layer of dead tissue in the wound bed 1
• It should not be confused with biofilm, exudates, or other wound debris, though these may coexist in chronic wounds 1
• Slough is part of the inflammatory process in wound healing and consists of dead white blood cells, bacteria, and wound debris 2, 3
• When present in a wound, slough can prevent or delay healing by:
  • Creating a physical barrier to epithelialization 3
  • Providing an environment for bacterial proliferation 3
  • Prolonging the inflammatory phase of wound healing 4

Identification in Wound Assessment

• In wound assessment terminology, slough is specifically identified when staging pressure injuries:
  • Stage III: Full-thickness tissue loss exposing subcutaneous fat where slough may be present but does not obscure the depth of tissue loss 1
  • Stage IV: Full-thickness tissue loss with exposed bone, muscle, ligament, or tendon where slough may be present 1
  • Unstageable: When slough or eschar completely covers the base of a full-thickness wound, preventing determination of the wound depth 1

Clinical Significance

• The presence of slough is associated with delayed wound healing and increased risk of infection 1
• Wounds with significant slough burden have higher bacterial loads, with each log10 increase in bacterial count associated with a 44% delay in healing time 1
• 80-90% of chronic wounds contain biofilm, which can develop within 10 hours of wound contamination and may coexist with slough 1
• Slough can contribute to an alkaline wound environment (pH 7.5-8.5), which further promotes bacterial growth and impairs healing 1

Management Approaches

• Sharp debridement is the preferred method for removing slough and necrotic tissue from wounds 1
• Other methods of debridement for slough removal include:
  • Autolytic (using hydrogels) 1
  • Biological (larval therapy) 1
  • Enzymatic (collagenase) 1
  • Mechanical (monofilament debridement pads) 5
• Dressings should be selected based on exudate control, comfort, and cost after slough removal 1

Clinical Pitfalls to Avoid

• Mistaking slough for biofilm can lead to inappropriate treatment strategies 1
• Failing to remove slough can result in:
  • Persistent inflammation 3
  • Increased risk of infection 1
  • Delayed wound healing 1, 4
• Aggressive debridement in patients with severe ischemia or pain requires careful consideration of risks versus benefits 1
• Antimicrobial dressings should not be used with the sole aim of accelerating healing after slough removal 1

Wound Classification

• When slough completely covers the wound bed and depth cannot be determined, the wound is classified as "unstageable" 1
• After removal of slough, the wound can be properly staged as either Stage III or IV depending on the depth of tissue involvement 1
• The presence of slough is a clinical indicator that the wound is not progressing through normal healing phases 4, 3