(PM3A) Biosurgical Wound Healing Flashcards
Define biosurgery.
Use of living organisms in medicine
Biocompatible materials
Biomaterials derived from natural sources
Give some examples of chronic wounds.
- Diabetic foot ulcers
- Pressure sores
- Leg ulcers
- Carbuncles (abscess)
- Necrotic tissue
What are the main goals for treatment of chronic wounds?
(1) Remove necrotic tissue
(2) Prevent infection of wound
(3) Encourage healing
What are the conventional treatments for chronic wounds?
(1) Debridement
(2) Gauze dressings + antiseptics
(3) Modern dressings which promote autolytic wound debridement
What is another name for maggot-based therapy?
Larval therapy
Maggot debridement therapy (MDT)
What is maggot-based therapy?
Use of maggots to clean non-healing wounds
What species of maggot is used in maggot-based therapy?
Green bottle fly
Phaenicia sericata
What is Phaenicia seracata?
The species of maggot used in maggot-based therapy.
How do maggots debride a wound?
Dissolve dead + infected tissue
Are maggots better at debriding gram-positive or gram-negative bacteria?
Maggots more effective at killing gram-positive bacteria than gram-negative bacteria
How are maggots thought to promote wound healing?
Reported to stimulate formation of granulation tissue
How do maggots break down dead flesh?
(1) Serine proteases (trypsin, chymotrypsin, etc)
(2) Aminopeptidases
(3) Allantoin and urea (factors that thin, soften and moisten skin)
What antibacterial substance does a maggot secrete?
Seraticin
What is seraticin?
An antibacterial substance secreted by maggots
Being developed at Swansea University
What secretions do maggots produce?
(1) Factors which breakdown dead flesh
(2) Seraticin - antibacterial substance
(3) Anti-inflammatory factors
Describe the life-cycle of a green bottle fly.
(1) Adult produces eggs
(2) Eggs last for 8-24 hours before hatching
(3) Larva hatch and live for 4-7 days
(4) After 4-7 days larvae turn into pupa
(5) After 10-20 days pupa hatch into green bottle flies
How are sterile maggots produced?
(1) Eggs are sterilised
(2) Eggs hatch and maggots are packed + shipped
(3) Maggots must be used within 8 hours of receipt
When do maggots stop feeding on necrotic/ infected tissue?
5 days after hatching
What is a BioBag dressing?
Maggots packaged with foam in pouch (foam protects maggots and soaks up secretions)
What is free-range larvae?
Maggots which are allowed free range in the wound
How is a free-range larvae dressing applied?
(1) Barriers (i.e. hydrocolloid dressing) applied to protect surrounding skin
(2) Apply maggots to wound
(3) Cover with a moist swab and perforated film dressing
(4) Leave for 3-4 days
(5) Dispose of used dressings and maggots from wound
How might a wound change when using maggot-based therapy?
- Become wetter as maggots produce discharge
- Active larvae may smell
- Potential tickling sensation
- Pain may increase if poor circulation
- Pain may decrease if infected
- Rash from secretions
- Development of a fever
How might pain of a wound change when using maggot-based therapy?
May increase if patient has poor circulation
May decrease if patient has infected wound
What types of wounds cannot be treated with maggot-based therapy?
(1) Dry wounds
2) Wounds in body cavities (e.g. mouth
How can a dry wound be treated using maggot-based therapy?
Application of a moist gauze swab
in which patient groups is maggot-based therapy less effective?
(1) >60 years old
(2) Deeper/ non-traumatic wounds
(3) Chronic limb ischaemia
What effect does chronic limb ischaemia have on maggot-based therapy?
Reduces effectiveness of treatment
What are some benefits of maggot-based therapy over conventional therapy?
- Improved healing time (more cost-effective)
- Can follow unsuccessful conventional therapy
- Antibacterial secretions can reduce infection
- Debride faster than conventional dressings
What are the four humours?
(1) Blood
(2) Phlegm
(3) Black bile
(4) Yellow bile
When are leeches deemed clinically appropriate?
- Plastic + reconstructive surgeries
- Impaired venous circulation
What are the benefits of using leeches in microsurgery?
(1) Drain blood from congested sites
(2) Relieving building pressure
(3) Prevention of blood clots in small veins in grafts
How much blood does a leech remove, on average, when it bites?
Approximately 5mL
How long does a leech bite wound bleed for?
10 or more hours
How much blood is lost from a leech bite wound?
Initially ~5mL
Up to 150mL for next 10 hours following detachment
What is the mechanism for the therapeutic benefit of leeches?
NOT from initial bite
From 10 or more hours of continued bleeding following leech removal, up to 150mL
How to leeches cause the bite wound to bleed for so long following removal?
Due to secretions, these include:
- Anticoagulant
- Local vasodilator
- Local anaesthetic
What are the main components of leech secretions (saliva)?
(1) Anticoagulant
(2) Local vasodilator
(3) Local anaesthetic
How long is leech treatment required to restore venous drainage?
3-5 days
What are the extensive components of leech secretions (saliva)?
(1) Hirudin
(2) Calin
(3) Destabilise
(4) Hirustasin
(5) Bdellins
(6) Hyaluronidase
(7) Factor Xa inhibitor
(8) Carboxypeptidase A inhibitors
(9) Acetylcholine
(10) Histamine-like factors
(11) Anaesthetic-like substances
What is hirudin?
Component of leech saliva
Inhibits coagulation by binding to thrombin
This prevents conversion of fibrinogen to fibrin
What is calin?
Component of leech saliva
Inhibits coagulation by inhibiting collagen-mediated platelet aggregation
What is destabilise?
Dissolves fibrin
What is hirustasin?
Inhibits serine proteases
What is bdellin?
Anti-inflammatory action
What is hyaluronidase?
Antibiotic, increases interstitial viscosity
What is a Factor Xa Inhibitor?
Inhibits coagulation
What is a carboxypeptidase A inhibitor?
Increase inflow of blood at bite site
What is acetylcholine?
Vasodilator
What are histamine-like factors?
Vasodilator
What is bivalirudin?
Hirudin analogue
Anticoagulant
Reversible
What is lepirudin?
Recombinant hirudin
Indicated for anticoagulation therapy in heparin-induced thrombocytopenia
What is the most common side-effect for hirudin-derived drugs?
Bleeding
What temperatures to leeches survive in?
4-15ºC
Cannot survive in direct sunlight
What water requirements do leeches have?
Do not tolerate chlorinated tap water
What food do leeches require to be kept alive for therapeutic use?
None
Can survive for months on a blood meal
What are the stages in application of a leech to a patient’s skin?
(1) Clean skin with soap + water, then rinse with distilled water
(2) Place a dampened square of gauze, with a hole in the middle, on affected area
(3) Select a lively leech and direct its head to hole in the gauze
(4) Attachment should occur quickly, if not use a needle prick to stimulate this
How long will a leech remain attached for?
30-60 minutes
What is a reason that a leech may detach sooner than intended?
Poor circulation
May detach to find a better site
What is important when collecting leeches in a container following treatment?
Labelled as USED
Dispose of leech
What happens to leeches used following treatment?
Collected and disposed of
How are leeches killed?
Sedated with 8% alcohol
Killed with 70% alcohol for 5 minutes
How are dead leeches discarded?
(1) Sluice
(2) Incinerator
Can a leech be used for a second time?
NO
Can a pharmacy accept a returned leech?
NO
What must happen following removal of leeches in treatment?
(1) Bleeding encouragement by removing any forming clot at wound site
- This must be completed regularly
(2) Routinely check area for infection
- Swab if indicators present
(3) Haemoglobin levels should be checked daily if bleeding is severely prolonged
If, following treatment with leeches, bleeding is severely prolonged from the wound what should be done by the healthcare professionals?
Measure haemoglobin levels daily
What is the main complication with leech treatment?
Infection
Are leeches sterile?
No
They have Aeromonas hydrophila in their gut
Which potentially harmful pathogen is present in leeches?
Aeromonas hydrophila
How is an Aeromonas hydrophila infection treated?
Antibiotics
When is leech treatment contraindicated?
Arterial insufficiency, e.g.
(1) Grafts - vulnerable to infection and leeches are not sterile
(2) Aeromonas hydrophila may become pathogenic in tissues with compromised arterial sufficiency
When can leech treatment be considered in patients with arterial insufficiency in the target tissue?
When the potential benefits outweigh the risks
