Question 7

College answer

Most marks were allocated to part d), and most candidates included the difficulty differentiating infection from SIRS and contamination from infection, however, this was the usual extent of the answer. Candidates should use the associated marking allocation throughout the question, to guide them to the breadth and depth of answers required

Discussion

With the exception of those who have worked in burns units, the trainees would have found themselves adrift here, unless they had purposefully read about this topic during their preparation.

Is this a "burns" question or an "infectious diseases" question? Well. If this were a question about fluid resuscitation in the burns patient, would it end up in the "fluids and electrolytes" section? The thermal injury is the unique aspect here, not the film of Pseudomonas. Ergo, it was grouped with the other burns-related questions.

a) Risk factors:

• Burn factors:
  • More than 20% BSA burns
  • Depth of burn
  • "age" of burn (delay to treatment)
• Patient factors:
  • Extremes of age
  • Impaired immunity
• Pathogen factors
  • Type and number of organisms
  • Heavy colonisation (bacterial counts over 10⁵ organisms per g of eschar)
  • Enzyme and toxin production
  • Motility
• Therapeutic factors:
  • Delays in burn wound excision
  • Topical therapy (instead of excision)

b) Local signs:

• Purulent drainage
• Foul odour
• Oedema and warmth
• Surrounding erythema
• Tenderness or increased pain
• Unexpectedly rapid separation of the eschar
• Conversion of an area of partial-thickness injury to full-thickness necrosis, or the appearance of necrosis in previously viable tissue
• Haemorrhagic discoloration of subeschar tissue

c) Systemic features:

• Fever or hypothermia
• Progressive tachycardia
• Refractory hypotension
• Increasing FiO2 requirements

d) Diagnostic challenges:

• Identification of local infection
  • Wound appearance is often obscured by dressings
  • The appearance of burns makes it difficult to identify infected tissue (eg. everything is oedematous and red)
  • Pathology speciments will inevitably grow organisms
  • Discriminating between colonisation and infection is difficult; not every lab may be able to do quantitative cultures
  • Pathogenic organisms (eg. some fungi) may not grow easily on normal culture media (Lago et al, 2021)
• Identification of systemic infection
  • The systemic response to burn injury mimics sepsis
  • Inflammatory markers (eg. WCC, CRP, procalcitonin) will be elevated even in wound colonisation
  • The patient may have infection elsewhere (eg. VAP), i.e. the wound is not the source