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FFICM > Burns > Flashcards

Burns Flashcards

1
Q

Define a burn

A

A coagulative destruction of the skin and its structures

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2
Q

What are the main mechanisms of a burn?

A

Thermal (note, scalding confers greater thermal energy than dry heat)
Electrical
Chemical
Mechanical

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3
Q

At what total body surface area (TBSA) is a burn considered “Major”?

A

15%

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4
Q

At what total body surface area (TBSA) is a burn likely to produce a SIRS response

A

25%

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5
Q

What are the main determinants of survival in burns?

A

%TBSA
Age
Inhalation injury

These are packaged into the modified Baux score

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6
Q

What is the name given to the pathological model of burns. Please describe it.

A

Jackson’s burn wound model. Describes 3 zones: 1) zone of coagulation, 2) Zone of stasis, 3) zone of hyperaemia and vasodilatation

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7
Q

How are burns classified?

A

Epidermal (no involvement of the dermis, red and painful, self limiting)
Superficial partial thickness (upper dermis)
Deep partial thickness (lower dermis)
Full thickness (extends through the dermis into underlying tissue)

Note: this is the UK model of description.

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8
Q

What is the modified Baux Score

A

Age + %TBSA + (17 x inhalation injury)

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9
Q

What is the current limit of survivability of the Baux score

A

160

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10
Q

List some burns prognostication scores other than the Baux score

A

Belgian outcome in burn injury score
Abbreviated burn severity index
Rockwood clinical frailty score (this last one isn’t burns specific, but may be helpful in contextualising the prognostication of burns patients)

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11
Q

Describe the appearance and sensation of a superficial partial thickness burn

A

Pale, pink and moist
Blisters form with fluid leak from blood vessel damage
They are very painful because of exposed nerve endings

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12
Q

Describe the appearance and sensation of a deep partial thickness burn

A

Drier than a superficial partial thickness burn. Tend to be red and non-blanching as the dermal plexus is coagulated by the heat
Less painful than superficial partial thickness

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13
Q

Describe the appearance and sensation of a
full thickness burn

A

Waxy and white
Not painful

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14
Q

Describe the main features of the “Zone of coagulation” in the Jackson burn model

A

Irreversibly dead tissue that acts as a nidus of infection and a reservoir of inflammatory products that can lead to systemic injury

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15
Q

Describe the main features of the “Zone of stasis” in the Jackson burn model

A

Hypoperfused, vasocontricted, alive but at risk tissue in proximity to the zone of coagulation. This tissue is at high risk of ischaemia, infection and necrosis. For this reason, burns may widen and deepen if this zone dies

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16
Q

Describe the main features of the “Zone of hyperaemia” in the Jackson burn model

A

Inflammatory mediators released from the zone of coagulation cause local vasodilatation, increased vascular permeability and oedema within this zone. When %TBSA exceeds 25%, the whole body effectively becomes the zone of hyperaemia and a profound SIRS response occurs

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17
Q

What is a key early surgical priority in the management of burns?

A

Early burn excision is aimed at reducing the nectrotic tissue load, infection risk and SIRS response. It is associated with improve survival

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18
Q

Burns is often described in two phases. What are these phases, and over what time frame do they occur?

A

The Acute Phase: occurs over the first 48 hours following burn during which vasodilatation, hypovolaemia and myocardial depression contribute to burns shock.
The Hypermetabolic Phase: occurs from 48 hours to around 1 year

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19
Q

If a burns patient is hypotensive at presentation to hospital, what is the most likely cause

A

It is almost certainly not from the burn itself; burns shock takes some time to manifest. If there are no overt other injuries, consider inhalation injury (carbon monoxide/Hydrogen Cyanide poisoning). Otherwise look for other trauma related injuries on the secondary survey and consider blood loss.

20
Q

Which poisons should one always consider in tandem with Burns?

A

Carbon monoxide
Hydrogen cyanide

One might also argue that you could consider recreational drugs or paracetamol if there is a suspicion that a depressed conscious level led to the injury

21
Q

At what level of COHb should you be concerned?

A

At 10% COHb patients are symptomatic
At 50% COHb patients generally enter coma

Levels over 30% are unambiguously considered “severe”

22
Q

What is the mechanism of action of carbon monoxide toxicity?

A

There are three mechanisms:
1) CO binds to Hb with x250 greater affinity than O2, blocking the binding of O2
2) CO causes a left shift of the OHDC inhibiting oxygen delivery at the tissues
3) CO causes competitive inhibition of michondrial cytochrome oxidase, inhibiting cellular utilisation of oxygen

23
Q

What are the indicators of severe CO poisoning?

A

New objective neurological signs (increased muscle tone, up-going planters)
Coma
ECG indications of ischaemia
Clinically significant acidosis
Initial COHb > 30%

24
Q

What is the half life of COHb at an FiO2 of 0.21?

A

6 hours

25
Q

What is the half life of COHb at an FiO2 of 1

A

90 minutes

26
Q

What is the standard treatment for carbon monoxide poisoning?

A

An FiO2 of 1 until COHb falls to < 3%.

This needs to be weighted up against the negative impacts of breathing high concentrations of O2.

27
Q

What is the treatment for hydrogen cyanide poisoning?

A

Hydroxycobalamin

28
Q

What is the mechanism of action of hydrogen cyanide poisoning?

A

Binds to the Ferric ion of mitrochondrial cytochrome A3 oxidase leading to:
Histotoxic hypoxia (oxygen is present, but cannot be utilised)
Lactic acidosis

Essentially it prevents aerobic respiration

Other mechanisms include:
Biogenic amine release leading to pulmonary and coronary vasoconstriction –> pulmonary oedema and cardiac failure
Stimulates neurotransmitter release causing neurotoxicity and seizures

29
Q

What indicators can be used to prompt to treat for hydrogen cyanide poisoning

A

Generally, have a low threshold to treat. However, the following should make the decision unambiguously:

Lactate > 7
Raised anion gap acidosis (presumably from the lactate)
Reduced AV oxygen gradient (oxygen cannot be used)
Haemodynamic instability in the context of an elevated lactate

30
Q

What is the mechanism of action of hydroxocobalamin?

A

Binds to HCN and forms non-toxic cyanocobalamin which is then renally excreted

31
Q

What is the treatment dose of hydroxocobalamin (cyanokit)

A

Adults: 5g over 15 minutes (repeat once if necessary)
Paediatrics: 70 mg/kg (up to 5 g max)

32
Q

What are the side effects of hydroxocobalamin treatment?

A

Transient hypotension
Reddish brown skin/membranes for up to 15 days
Urine discolouration for up to 35 days

Note, these discolourations can impact on equipment:
colorimetric laboratory tests can be error. Haemofiltration blood in line alarms can be triggered. COHb will be falsely elevated by around 5%

33
Q

List a couple of methods of estimating %TBSA

A

Lund and Browder chart
Wallace rule of nines

34
Q

How long should you irrigate an acid burn for?

A

45 minutes

35
Q

How long should you irrigate an alkali burn for?

A

1 hour

36
Q

What might prompt you to intubate a burns patient?

A

Reduced conscious level
Evidence of deep neck, peri-oral or intra-oral burns
Respiratory distress

Generally have a low threshold to intubate. It’s better to intubate and extubate a few days later following a successful leak test, than to try and intubate in a crisis with a closing airway.

37
Q

You are looking after a burns patient with 40% TBSA coverage. Their temperature is 35 degrees. How should you proceed?

A

Do whatever you can to prevent further heat loss, and warm the patient actively (warm fluids etc.). However, this is a loosing battle and you need to prioritise getting them to the burns centre where they have specialised equipment and heated rooms. Do not delay transfer in order to try and rewarm them as it is likely their body temperature will only continue to drop.

38
Q

Is suxamethonium safe to use in burns?

A

For the first 48 hours, yes. After that, no.

39
Q

What is an escharotomy, when is it required, and how should it be performed?

A

These are cuts made into the burn to release constrictive tissue. They are mandatory in any circumferential burn of the chest, abdomen or limbs. They should be performed by a surgeon, prior to transfer to the burns unit and with diathermy. Ventilation may be impossible without them. Don’t forget antibiotics.

40
Q

Are there situations where a non-circumferential burn may require an escharotomy?

A

Clearly.
In children, non-circumferential burns to the chest and abdomen by impair ventilation and still require escharotomy

41
Q

How should you calculate the fluid requirement for a burns patient?

A

By the parkland formula

42
Q

Define the parkland formula, and when and how to apply it?

A

Total requirement in first 24 hours = 2-4 mL x actual body weight (kg) x %TBSA
Using 3 mL is a sensible middle ground to start.
Start the clock from the time of the burn
Give half in the first 8 hours, and the other half in the next 16 hours.
Subtract any fluid already given.

Use a warmed isotonic balanced crystalloid
Aim for a urine output of 0.5-1 mL/kg/hr.

Some are concerned that this formula may over-do it slightly. Hence the use of urine output as a physiological marker.

43
Q

If urine output drops during burns fluid resuscitation, how should you proceed?

A

Consider other causes besides hypovolaemia (such as Rhabdo).
Increase the rate of fluid administration to the full 4 mL of the parkland.
If still not improving, consider “colloid” rescue with 1/3 of the crystalloid regimen being replaced by 4.5% albumin

44
Q

What are the criteria for diagnosing sepsis in burns?

A

Temp > 39 or < 36.5
HR > 110
RR > 25 or MV > 12L
Thrombocytopenia < 100
Glucose > 11.1, or insulin > 7 units/hr
Intolerence to enteral feed

Generally, biomarkers like CRP are not useful. PCT may be of use.

45
Q

How does the basal metabolic rate of burns patients change?

A

It is much higher than their non-burn counterparts. At 40% TBSA it is double.

46
Q

Which respiratory marker is correlated with outcome following inhalation injury?

A

P/F ratio

47
Q

What is the role of bronchoscopy in inhalation injury?

A

Diagnose and grade inhalation injury
Early clearance of particular matter and washout

FFICM (3 decks)

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