Week 2 - skin and coat disorders

Skin allergies, principles of wound healing and management, skin grafts

What is the name for hives or reaction bumps?

Urticaria

Why does urticaria occur?

Due to allergic reaction causing raised reddened circumscribes areas of erythema and oedema that are usually pruritic

What is the pathophysiology of urticaria simple?

Allergy trigger > mast cells release histamines > histamines released into capillaries and boost blood flow causing inflammation > additional chemical messengers respond > blood vessels dilate and become leaky > extra fluid oozing into surrounding tissue causes swelling and itching

What does an allergy trigger do to the immune system?

Launches the immune system into defence

Why does inflammation occur with urticaria?

Histamines are released into capillaries and boost blow flow into the affected area

Why do blood vessels dilate and become leaky?

To allow WBC and other protective substances to pass and prepare to fight

What causes swelling and itchiness with urticaria?

Extra fluid oozing into surrounding tissues and nerves

What can be done to test triggers for urticaria?

Skin allergy testing

What are 3 diagnosis tools for urticaria?

Serum allergy testing, intradermal testing, blood tests

What is the treatment for urticaria?

Exclusions of identified allergens, allergen specific immunotherapy, corticosteroids, essential fatty acids, antihistamines

Name a 5 factors that would affect wound healing?

Age, wound position, movement, systemic disorders, patient interference

What are wound drains?

Implants that allow removal of fluid/gas from a surgical or traumatic wound

What are the positives of wound drains?

Relieve pressure, allow easy sampling of fluid during healing, eliminate dead space, and remove inflammatory mediators, bacteria, foreign materials, necrotic tissue

What are complications of wound drains?

Higher risk of infection, vascular damage, blockage, electrolyte imbalance

What kind of infection can occur with wound drains?

Ascending infection and FB reaction to the drain

What vascular damage can occur with wound drains?

Pressure necrosis of the arterial wall

What blockage can occue with wound drains?

Clogged, lose suction, failure

What electrolyte imbalance can occur with wound drains?

High fluid production and loss leading to metabolic derangements and hypoproteinaemia

What are the types of wound drains?

Open and closed systems

What are open systems?

Open to the environment allowing fluid to drain out

Give an example of a passive drain and material made up of

Penrose drain made of latex

How do passive drains work?

Capillary action, gravity, pressure gradients caused by body movement, overflow of fluid from the wound

How should a passive drain be placed and how long for?

Exit through a separate stab incision away from the main surgical site for 48-72hrs

What are active drains?

Closed systems that collect fluid into a resevoir

What is an example of an active drain?

Closed suction drains

How do active drains work?

Artificial pressure gradient, prevents saturation of bandage material, decreases risk of ascending infection, limits exposure to staff/patients of contaminated fluid

How long should active drains be placed for?

3-5 days

What are skin grafts?

Surgical procedure that transplants healthy skin from a donor site to cover damaged, missing, or diseased skin

What would happen if a wound has too much tension?

Tension will cause wound edges to break down

How do skin grafts work?

Grafts are taken from areas with loose skin from the same animal > placed onto a healthy granulation tissue bed > this forms new blood supply forms and the graft must remain immobile to allow attachment and revascularisation

What is the care for skin grafts?

Movement must be restricted to prevent graft failure, bandages changed every 3-4 days for 3 weeks, monitor colour changes for graft health and failure, ensure graft site remains clean and protected

What colour is the skin graft on day 1?

Pale

What colour is the skin graft on day 2-3?

Blue/black (haemoglobin products absorbed)

What colour is the skin graft on day 3-4?

Light red

What colour is the skin graft on day 7-8?

Red