Chapter 81: Burns

Question 1

What are the 4 etiological classifications of burns?

Answer 1

• Thermal
• Chemical
• Electrical
• Radiation

Question 2

What are the 5 degrees of thermal burns?

Answer 2

1st degree: Superficial, only epidermis effected. No blistering, wounds or scarring
2nd degree: Full thickness epidermal necrosis extending into underlying dermis. Results in blistering (rare in dogs/cats)
3rd degree: Extends through dermis to underlying SQ
4th degree: Extend to underlying muscle or fascia
5th degree: Extends to bone

Question 3

What occurs when the skin temperature reaches 40-44C?
60C? and 70C?

Answer 3

40-44C: Failure of cell membrane Na pump
60C: Epidermal necrosis within 1 second
70C: Full-thickness burns in less than 1 second

Question 4

What is the rule of 9s?

Answer 4

A method of estimating the % surface area effected by a burn
- Head and neck 9%
- Each thoracic limb 9%
- Each pelvic limb 18%
- Dorsal and ventral trunk 18% each

Question 5

What are the three zones of tissue injury secondary to thermal burns?

Answer 5

Moving outward from point of greatest energy:
- Zone of coagulation: no viable tissue remains
- Zone of stasis: reduced perfusion due to damage to RBC membrane proteins causing reduction in deformability and reduced luminal diameter due to increased interstitial pressure from increased capillary permeability. **Tissues in this zone may be saved or may deteriorate (vulnerable)
- Zone of hyperemia - Primary zone of the inflammatory response

Question 6

What causes vasodilation as an acute response to a burn injury?

Answer 6

• Postganglionic autonomic stimulation
• Upregulation of nitrous oxide synthesis within the burned area and surrounding skin

Question 7

Why do burns heal slower that usual?

Answer 7

• Only 5% of normal levels of fibroblast growth factor -2 (FGF-2)
• None of the capillary endothelial chemotactic and proliferative activity seen in normal surgical wounds

Question 8

List the main toxins associated with smoke inhalation:

Answer 8

• Carbon monoxide (preferentially binds Hgb)
• Hydrogen cyanide (binds mitochondrial cytochrome oxidase, disrupting electron transport and preventing cellular respiration)
• Inorganic acids (intensely irritating causing bronchospasm and laryngospasm)

Question 9

What pathophysiological changes occur in the lungs in response to smoke inhalation?

Answer 9

• Increased pulmonary vasculature permeability
• Venoconstriction
• Rapid accumulation of fluid, mucus and neutrophils within the alveoli and airways

Pulmonary edema

Question 10

What are the main sources of the cytokines causing the changes resulting in ARDS?

Answer 10

• Smoke damaged lungs
• Burn-injured tissues
• GIT

Question 11

What is the pathophysiology of systemic vascular permeability in response to a major burn injury?

Answer 11

Within 10 minutes (burns over 25%), systemic vascular permeability to fluid and albumin increases because of myosin-mediated contraction of vascular endothelial cells and direct damage to endothelial cells

Mediated by complement, histamine and oxygen free radicals from the burn site

Question 12

When does generalized edema and hypovolemia peak after burn injury?

Answer 12

Within the first 12 hours

Question 13

What are the main sources of fluid loss in burn patients?

Answer 13

• Extravasation
• Evaporative (3-20 times greater)

Question 14

What are the main causes of myocardial effects of burn patients?

Answer 14

• Decreased left ventricular contractility (increase of myocyte intracytoplasmic Ca)
• Myocardial damage and decreased cardiac output secondary to carbon monoxide (decreased ATP production and necrosis)

Question 15

How is the GIT effected by burns?

Answer 15

• Barrier is compromised leading to translocation of bacteria and endotoxins as well as cytokines leading to septic shock
• Increases apoptotic rate of gut mucosa
• Impaired motility (increased expression of inducible nitrous oxide from myenteric plexus)

Question 16

What substance may have a protective role against acute renal injury in burn patients?

Answer 16

Atrial natriuretic peptide - increases renal blood flow and urine output

Question 17

What is burn anemia?

Answer 17

An immediate and long-lasting reduction in circulating erythrocyte numbers
- Membrane damage increase fragility and decreased deformability
- Intravascular hemolysis
- Decline in protective antioxidants glutathione and alpha-tocopherol
- Reduced erythropoiesis

Question 18

How is the immune system effected in severe burn injuries?

Answer 18

Significant negative effects on lymphocyte production and function
- Upregulation of lymphoid apoptosis (TNFa)
- Inhibition of chemotactic cytokine production by T-cells leading to an increased susceptibility to sepsis
- Macrophages and neutrophils express a hyperinflammatory phenotype
- Neutrophil migration is suppressed and adhesion is increased leading to vascular damage

Question 19

How do electrical burns form?

Answer 19

Due to the heat that is generated by the resistance of the tissues to the current flow

Question 20

What is Joule’s law?

Answer 20

J = (I^2)RT
Energy delivered to tissue is proportional to the tissue resistance (R), the duration of exposure (T), and the square of the amperage (I)

Therefore, predicts that tissue with a higher resistance will sustain greater damage than those with lower resistance

Bone has a much higher resistance than surrounding soft tissues

Question 21

What is bronchial hygiene therapy?

Answer 21

Treatment performed to remove accumulated secretions, necrotic material, foreign debris and bacteria from the airways
- Nebulisation and coupage
- Bronchoscopy and saline lavage

Question 22

How do you use a veterinary burn card?

Answer 22

It is 45 cm square. You divide the burn area into cards and multiply by 0.45 = square meters of surface area burned
Then use the weight to surface area table on the back t find total area of dog
Burn area / total area x100% = burn percentage estimate.