The topic of burns appears in the Part II CICM exam in a number of ways. Typically, as a part of the question, the candidate is either expected to list the characteristic findings of airway burns and smoke inhalation injuries, or to discuss fluid resuscitation for the burns patient. Whenever this is not the case, a generic "discuss your management" question is to be expected. Occasionally the patient is paediatric, but the "paediatricity" of the patient does not exert overmuch influence on the discussion of the burns management.
Previous questions on this topic have included the following:
The LITFL burns entry from the CCC is an invaluable resource, dense with useful information. Virtually the same information is offered below, reorganised with the specific goal of answering the abovementioned CICM SAQs.
Important clinical features in the assessment of burns
Key features in the clinical assessment of the burns patient
- look for signs of Airway burns
- Features of carbon monoxide or cyanide poisoning
- Hypotension, hypovolemia, adequacy of fluid resuscitation;
Also, problems gaining vascular access (not through the burn, unless you have no choice).
Other important burn patterns:
- Presence of circumferential burns
- Presence of corneal, perineal or genital burns
- Decreased level of consciousness, head injury; analgesia
- Electrolyte disturbance: hyponatremia and hyperkalemia
- Exposure and assessment of total burned areas
- Urine output (the most important parameter to guide fluid resuscitation)
- Haematocrit: haemoconcentration is a sign of volume depletion
- Temperature: the patient may either still be hot from the fire (in which case, put them out) or - more likely - they will be hypothermic from their loss of thermoregulation (in which case, expose them to radiant heat to maintain normothermia).
Estimation of the affected body surface area
Palmar surface method
- Surface area of a patient's palm (including fingers) = 0.8% of total body surface area.
- Palmar surface are can be used to estimate relatively small burns (< 15% ) or very large burns (> 85%).
- For medium sized burns, it is inaccurate.
Wallace rule of nines
- A good method estimating medium to large burns in adults.
- The body is divided into areas of 9%, and the total burn area can be calculated.
- 9% for each arm
- 18% for each leg
- 18% for the front of the torso
- 18% for the back of the torso
- 9% for the head
- 1% for the perineum
- It is not accurate in children.
Lund and Browder chart
- the Lund-Browder Chart is the most accurate method.
- It compensates for the variation in body shape with age and therefore can give an accurate assessment of burns area in children.
Differential diagnosis of unconsciousness in the burns patient
For some reason, in the college questions all the burns patients are unconscious, and the candidates must determine why. A list of differentials may be generated, which must be broad:
Burn and trauma-associated:
- Traumatic brain injury
- Carbon monoxide poisoning and thus hypoxia
- Cyanide poisoning and thus hypoxia
- Intoxication
Generic differentials:
- Stroke
- Intracranial infection
- Hypoglycaemia
- Post-ictal state
- Cerebral vasculitis
- Hypothyroidism/hypoadrenalism
Classification of burns depth
The table below comes from the Clinical Practice Guidelines of the Royal Children's Hospital in Melbourne.
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Depth
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Cause
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Surface/colour
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Pain sensation
|
|
Superficial
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Sun, flash, minor scald
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Dry, minor blisters, erythema, brisk capillary return
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Painful
|
|
Partial thickness-superficial
(superficial dermal)
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Scald
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Moist, reddened with broken blisters, brisk capillary return
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Painful
|
|
Partial thickness- deep
(deep dermal)
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Scald, minor flame contact
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Moist white slough, red mottled, sluggish capillary return
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Painless
|
|
Full thickness
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Flame, severe scald or flame contact
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Dry, charred whitish. Absent capillary return
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Painless
|
Devgan et al (2006) describes several ways of measuring the depth of a burn. In short, burns are classified according to depth: epidermal, superficial partial-thickness, deep partial-thickness, and full-thickness. These ccategories are usualluy determined at the bedside.
Clinical methods:
- Wound appearance
- Capillary blanching and refill
- Capillary staining
- Burn wound sensibility to light touch and pinprick
Instruments:
- Thermography is a measurement of wound temperature. Temperature is taken as an indicator of wound depth; this is based on the expectation that deeper burns will have less persuion on their surface, and will therefore be colder. This technique has the major disadvantage of being significantly dependent on ambient temperature. If the evaporative heat loss from the wound has been significant (eg. if you dutifully washed it with cold water as you're supposed to) the wound will be colder and therefore will appear deeper to the thermographer. One might concieve of a situation where this leads to an unnecessary escharotomy.
- Fluorescent dye infusion: like thermography, this is a method of assessing near-surface perfusion of a burns wound. The theory is that a poorly perfused full-thickness burn will have less dyne circulating in it, and therefore will not fluoresce under UV light. Though this method sounds really cool, it is unfortunately limited by poor light penetration under eschar, dye escape out of leak capillaries and the renal clearance mechanisms of fluoresceine.
- Laser fluorescence videography is alos a dye-based method, but this time using a laser to make the dye show up. It has the advantage of being able to dynamically demonstrate tissue perfusion, but has all the disadvantages mentioned above (dye clearance, eschar etc). This modality has evloved to include fancy perfusion measurements such as laser Doppler.
Problems with these methods:
- Burns wound conversion: superficial burns tend to evolve into deeper burns over time, motivated by mechanisms which are thus far poorly understood. Assessment of burn depth is therefore a dynamic process.
- Clinical assessment is inaccurate for intermediate burns: people are more easily able to spot superfical burns and full-thickness burns. Everything in the middle ends up a bit muddled. Heimbach et al (1984) found that clinical depth estimates are accurate only about two-thirds of the time.
- Clinicians vary in their assessments; experience is required to make a valid assessment (i.e. the more burns you have seen, the better you are at assessing burns - which makes sense)
Gold standard:
- Punch biopsy with histology: this is really the only way you can be truly sure how deep the wound is, but it is rarely practical to do this (and -as mentioned above- this is going to change as the burn wound undergoes conversion). Punch biopsy reveale protein coagulation, microvascular occlusion and tissue devitalisation; it is the method against which all other methods are compared.
Management of severe burns
Immediate priorities: the primary survey of burns
- Assessment of the airway and of the need for immediate intubation
- May require awake fiberoptic or surgical airway
- Ventilation with high FiO2; investigation of possible carbon monoxide poisoning with ABG, and investigation for pulmonary thermal injury with CXR.
- Establishment of secure vascular access, and the administration of crystalloid to replace intravascular volume.
- Adequate analgesia and sedation
- Exposure minimisation and management of heat loss
Specific management issues:
Heat and fluid loss
- These people lose heat and water through the burnt regions
- The recommendation is to cover the burns with cling film
Escharotomies
- Only the burnt tissue is divided, not any underlying fascia, unlike a fasciotomy.
- Incisions are made along the midlateral or medial aspects of the limbs
- For the chest, longitudinal incisions are made down each mid-axillary line to the subcostal region
- Escharotomies are best done in theatre with electrocautery, as they tend to bleed.
- They are then packed with Kaltostat alginate dressing and dressed with the burn.
Fluid resuscitation
- This is covered in a whole separate chapter. In brief:
- Parkland formula: 4ml/kg/% of body surface area, for first 24 hrs
- First half of the volume given over the first 8 hours
Transfer to a burns unit
- If you do not have experience managing burns patients, you should transfer the patient to somebody who does.
- LITFL lists the following indications for transfer to a burns unit:
- Burns > 10 % TBSA in an Adult
- Burns > 5 % TBSA in a Child
- Full thickness burns > 5% TBSA
- Burns of face, hands, feet, perineum, genitalia, and major joints
- Circumferential burns
- Chemical or electrical burns
- Burns in the presence of major trauma or significant co-morbidity
- Burns in the very young patient, or the elderly patient
- Burns in a pregnant patient
- Suspicion of Non-Accidental Injury
