Chapter 81 Burns

Question 1

List the four etiologic classifications of burns:

Answer 1

• Thermal: caused by tissue exposure to temperature extremes (either high or low) sufficient to cause cellular damage
• Chemical: result from exposure to chemicals that cause tissue necrosis, either directly via chemical reactivity or indirectly via secondary thermal effects
• Radiation: caused by exposure to ionizing radiation at levels that cause acute cell death
• Electrical: occur when an electrical current of sufficient energy passes through the patient, causing cellular necrosis along its path

Question 2

List the definitions of 1st - 5th degree burn.

What is the other ‘system’ of classification?

Answer 2

First degree is epidermal only

Second degree involve full-thickness epidermal necrosis that extends into the underlying dermis

Third degree extend completely through the dermis to the underlying subcutaneous tissue.

Fourth degree extends to muscle

Fifth degree extends to bone

Alternatively, can describe as partial thickness vs full thickness

Question 3

Label the diagram

Answer 3

• Zone of coagulation:* (aka. -necrosis/destruction): no viable tissue remains.
• Zone of stasis:* reduced perfusion due to reduced deformability of RBCs, and reduced vascular luminal diameter given increased capillary permeability (which is proportional to severity of burn). This tissue is vulnerable, effective therapy can restore viability.
• Zone of hyperaemia:* primary area of inflammatory response. Tissue viable and will heal.

Question 4

The affinity of Carbon Monoxide for Haemoglobin is how many times greater than that of Oxygen?

Answer 4

x240

Question 5

What is ‘burn shock’?

Answer 5

Hypovolaemia due to increased systemic vascular permeability and evaporation of fluid from burn wound.

Question 6

Immediately post-burn, the body enters a period of hypometabolism (“ebb” stage), followed by hypermetabolic state. Basel energy expenditure during hypermetabolic state increased by >XXXX c.f. pre-burn expenditure:

Answer 6

Increased by 100%

Question 7

What is the formula for Joule’s law and what does it measure

Answer 7

Rate at which resistance in a circuit converts electric energy into heat energy i.e. in burns calculates the total energy delivered to tissues

J = I²RT

(R = resistance, I = amperage, T = duration of exposure)

Question 8

What are the three ways that heat can be transferred to tissues?

Answer 8

Conduction direct contact with a hot object

Convection airborne heat transfer, such as the superheated air in a house fire

Radiation electromagnetic energy interacts with the body and is converted to heat

Question 9

Re percentage total body surface area, what two ways can it be estimated

Answer 9

• Wallace’s rule of 9s
  
  • Each region 9%
    
    • each FL
    • head and neck
  • Each region 18%
    
    • each HLs
    • dorsal trunk
    • ventral trunk
• Veterinary Burn card: credit card is 45cm². (No cards in burn area x 45/100)/body surface area (see chart)

Question 10

How does healing of burns compare to healing of other wounds?

Answer 10

Slower, lower concerntrations of healing cytokines found in burn fluid

Question 11

List the 3 mechanisms by which carbon monoxide exerts toxic effects

Answer 11

• Preferential Hb binding
• Shift of oxygen dissociation curve to left
• CO binding to myoglobin –> reduced oxygen availability to muscle

Question 12

List physiologic changes that occur in lung’s response to smoke inhalation

Answer 12

• Increased pulmonary vascular permeability
• Venoconstriction
• Atelectasis
• Deactivation of surfactant
• Decreased compliance

–> pulmonary oedema/ARDS

Question 13

How is the GIT affected by burns?

Answer 13

Produce cytokines/major effector organ for burn SIRS/MODS, increased apoptosis of mucosal cells (without increased proliferation) –> bacterial translocation

Question 14

Brifly list the effects that burns can have on the following organ systems:

Lungs

Cardiovascular

Cardiac

GIT

Renal

Haematopoeitic

Immune

Neurologic

Endocrine/metabolic

Answer 14

Lungs: Pulmonary oedema/ARDs

Cardiovascular:‘Burn shock’ due to exttravasation and evaporation

Cardiac: Reduced myocardial function

GIT: Effector organ of SIRS/MODS, increased mucosal death –> translocation

Renal: Risk of ARF proportional to burn severity

Haematopoeitic:‘Burn anaemia’; cells lost and also intravascular haemolysis, depressed erythropoetin release

Immune: Negatively affects lymphocyte production and function. Macrophages and neutrophils becoma hyperinflammatory

Neurologic: Hyperalgesia, chronic cathecholamine release

Endocrine/metabolic: 100% increased energy expenditure –> catabolism, hypothalamic set point increased by 1-2 ºC

Question 15

How does the energy source in burn patients differ from normal?

Answer 15

Increased relaince on protein catabolism (30%) in burn patient, usually <10%

‘Burn diabetes’

Question 16

What are the 3 key areas of burn management

Answer 16

1. First aid
2. Treatment of systemic complications
3. Tretament of burn wounds

Question 17

What is first aid tx of burns

Answer 17

• Cool water (ideally 15ºC, ice contraindicated), beneficial even up to 3 hours post injury.
• Sterile, occlusive, non-adhesive dressing

Question 18

List some treatments for management of systemic complications of burns

Answer 18

Cardiovascular: Treat burn shock (L-lactate potentially superior to racemic lactate Lactated Ringer’s Solution (D-lactate shown to inc production of reactice oxygen species)). Maintain UOP 1-2 ml/kg/hr

Lungs: Monitor for inhalation injury, consider bronchoscopy + tracheal culture + saline lavage. Nebulisation + coupage. Consider bronchodilators e.g. epinephrine

Oxygen for lungs and tissues. 40% FiO2 reduced carbonmonoxide half life from 4 hrs to 1 hr.

Question 19

For purposes of analgesic management burn pain has been divided into 3 phases, what are they?

Answer 19

1. Acute (2-3d)
2. Healing (until re-epithelialised)
3. Rehabilitation (months - years)

Question 20

List 6 management strategies that can help to manage/modulate the hypermetabolic/catabolic state of burn patients

Answer 20

1. Warm (29-33ºC), humid environment
2. Burn covered
3. Analgesia/sedation/sleep
4. High content (25% caloric intake), highly digestible protein diet
5. Beta-blockers (titrated to 20% reduction in HR)
6. Insulin

Question 21

List 5 debridement techniques for large burns

Answer 21

• Sharp surgical
• Ultrasonic surgical
• Hydrosurgical
• Autolytic
• Cerium nitrate (a rare earth metal that strongly interacts with calcium. Binds to eschar –> tough impermeable eschar, which remains in situ for weeks –> reduced sepsis and mortality cf other tx)

Question 22

What is degree of chemical burn proportional to?

Answer 22

Quantity, concentration, toxicity, duration of exposure

Question 23

What are the mode of action for burn in folowing chemicals?

Acids

Alkalis

Hydrocarbons

What are ‘vesicants’? Give an example

Answer 23

Acids are powerful oxidizing agents, disrupting protein structure and function by insertion of oxygen atoms into peptide bonds.

Alkalis are reducing agents, denaturing protein through reduction of amide bonds that cross-link polypeptide chains; these reactions can be intensely exothermic, causing simultaneous thermal burns.

Hydrocarbons act as lipid solvents that disrupt cytoplasmic membranes.

Vesicants are chemical agents that cause blistering; this group of compounds is defined based on its effects rather than chemical composition e.g. doxorubicin

Question 24

How can doxorubicin extravasation be treated?

Answer 24

• Infiltrate with hyaluronidase –> promotes vascular uptake
• Infiltrate with free radical scavenger e.g. dexrazoxane
• Surgical excision

Question 25

Joule’s law predicts that tissues with higher electrical resistance will sustain greater damage than tissues with lower resistance. Bone has a much higher electrical resistance than the surrounding muscle and fascia; it also dissipates heat more slowly because of its higher density and lower water content. What is the net effect of this?

Answer 25

Superficial skin injury can be minor, while in deeper levels, bone and adjacent muscle, fascia, and neurovascular structures have sustained severe damage.

i.e. pay close attention to surrounding/deeper tissue in electrical burns

Question 26

How shoudl cold burn be treated initially i.e. first aid

Answer 26

tepid/lukewarm warming (40-42 ºC).

Do not thaw if risk of re-freezing - better to wait.