Biosurgical Products

Question 1

what is the principle of treatment of chronic wounds

Answer 1

Remove necrotic (dead) tissue
Prevent wound infection
Encourage healing

Question 2

what are conventional treatments for wound care

Answer 2

Debridement by surgical/sharp, mechanical, chemical, enzymatic or autolytic removal of dead tissue

Traditional gauze dressings and antiseptics (cheap but require more care)

Modern dressings that promote autolytic wound debridement and prevent infections (i.e. Hydrogel, hydrocolloid, alginate dressings etc) are expensive but improve healing times (average time to healing 89 days) and require less care

Question 3

what are alternatives to conventional wound care and what is it?

Answer 3

use of maggots -
Also known as larval therapy or maggot debridement therapy (MDT)

Use of live maggots to clean non-healing wounds

Clinical applications of use sterile larvae of the green bottle fly (Phaenicia sericata)

Question 4

why is maggots used in clinics

Answer 4

Long history of their clinical use and benefits

Question 5

how does maggots help with wounds?

Answer 5

Maggots debride (clean) wounds by dissolving dead, infected tissue
200 maggots can consume up to 15 grams of necrotic tissue per day

Maggots disinfect wounds by killing bacteria (even in cases when antibiotics are ineffective)
Maggots more effective at killing gram-positive bacteria than gram-negative bacteria

Maggots prevent further infection of wounds

Maggots actively promote wound healing
Reported to stimulate formation of granulation tissue

Question 6

maggots secretion

Answer 6

Contain factors to breakdown “dead” flesh
Serine proteases (trypsin, chymotrypsin etc)
Aminopeptidases
Allantoin and urea (factors that thin, soften and moisten skin)

Antibacterial substances
Seraticin (new antibiotic being developed by researchers at University of Swansea)

Anti-inflammatory factors

Question 7

life cycle of a green bottle fly - breeding cycle.

Answer 7

eggs
larva - 4-7 days
pupa-10-20 days
adult

Question 8

Production of sterile maggots

Answer 8

Fly eggs are sterilised
Eggs hatch and the sterile maggots are packaged and shipped
Maggots must be used within 8 hours of receipt
Maggots will stop feeding 5 days after hatching

Question 8

Production of sterile maggots

Answer 8

Fly eggs are sterilised
Eggs hatch and the sterile maggots are packaged and shipped
Maggots must be used within 8 hours of receipt
Maggots will stop feeding 5 days after hatching

Question 9

how are maggots applied?

Answer 9

Free-range larvae applied directly to the wound

Contained larvae dressings (i.e. BioBag dressings)
Maggots packaged with foam in pouch (foam protects maggots and soaks up secretions)
Preferred by patients

Barriers (i.e. hydrocolloid dressing) applied to protect surrounding skin

Apply maggots to wound (number depends on surface area and depth of wound)

Cover with a moist swab and perforated film dressing

Leave for 3-4 days

Dispose of used dressings via clinical waste

Wash maggots from wound (discard in clinical waste)

Question 10

what might patients notice with maggot treatment

Answer 10

Their wound might change….

Become wetter as a dark red/pink discharge is released when maggots breakdown dead tissue

Smell from active larvae (especially if wound contains much dead tissue)

Some report tickling sensation

If patient has poor circulation, pain may increase

If wound is infected, pain may decrease

Secretions may cause a rash

They may develop a fever.

Question 11

What wounds cannot be treated with maggots?

Answer 11

Dry wounds (but a moist gauze swab may be sufficient to provide moisture)

Wounds in body cavities

Question 12

Why consider maggot therapy over conventional therapy?

Answer 12

Difficult to treat or wounds unresponsive to treatment

Maggots have been shown to clean wounds (debridement) more quickly than conventional dressings

Maggots can aid the management of infected wounds through anti-bacterial secretions
MRSA infection eliminated in 92% patients within 3 weeks with maggot therapy (range 1- 6.5 weeks) compared to 28 weeks with conventional treatment (range 3-60 weeks)

Faster healing times achieved with maggot therapy can benefit patient and can also be cost effective.

Question 13

what are Accepted clinical uses of leeches

Answer 13

Proven to be valuable for plastic and reconstructive surgery (i.e regrafting amputated appendages, skin grafts)

Useful in cases of impaired venous circulation, but not insufficient arterial inflow.
Relatively easy for surgeons to reconnect arteries but not veins

Leeches produce a small bleeding wound that mimics a venous circulation in compromised tissue.

Question 14

what are the Benefit of Leeches in Microsurgery

Answer 14

Drain blood from congested sites

Relieve building pressure

Prevent blood clotting in small veins in graft

Question 15

How do leeches do it?

Answer 15

Main therapeutic benefits are not derived from the blood removed during biting (average 5ml)

Therapeutic benefit obtained from the fact that each bite wound continues to ooze up to 150ml of blood for 10 or more hours after leech detachment.
Drain pooling blood and relieves building pressure in graft

Continued bleeding promoted by leech secretions, including an anticoagulant, a local vasodilator and local anaesthetic
Coaagulant (leech-dervived or conventional) not sufficient alone!

After 3-5 days vessel ingrowth sufficient to restore venous drainage and treatment can be terminated!

Question 16

what are Substances in leech “saliva” and their roles

Answer 16

Hirudin - inhibits coagulation by binding to thrombin
Calin - inhibits coagulation by inhibiting collagen-mediated platelet aggregation
Destabilise - dissolves fibrin
Hirustasin - inhibits serine proteases etc
Bdellins - Anti-inflammatory action
Hyaluronidase - Antibiotic, increases interstitial viscosity
Factor Xa inhibitor - inhibits coagulation
Carboxypeptidase A inhibitors - increase inflow of blood at bite site
Acetylcholine - vasodilator
Histamine-like factors - vasodilators
Anesthetic-like substances

Question 17

what is hirudin and its role

Answer 17

Potent anti-coagulant in leech saliva
Prevents blood from clotting by binding to and inactivating thrombin, thus inhibiting conversion of fibrinogen to fibrin

Question 18

what are examples of Leech-derived drugs

Answer 18

Hirudins - direct inhibitors of thrombin

Bivalirudin
A hirudin analogue
Unlike hirudin, binding of bivalirudin to thrombin is reversible
Indications- anticoagulation for patients undergoing PCI
Most common side effect is bleeding

Lepirudin
Recombinant hirudin (identical to hirudin but for 1 amino-acid substitution)
Indicated for anticoagulation therapy in heparin-induced thrombocytopenia
Most common side effect is bleeding

Question 19

how do you Care for leeches

Answer 19

Temperature
Leeches like cool temperatures (4-15˚C)
Special care and attention required if leeches are to be used in a heated hospital ward.
Keep them as cool as possible until they are needed.
Never put leeches into direct sunlight.

Water
Avoid chlorinated tap water
Distilled water + HirudosaltTM for consistency

Container
Must have a lid with only small perforations to prevent escape!!

Food?
Unnecessary as leeches can live for months on a blood meal

Question 20

how can you apply the leeches

Answer 20

Clean patient’s skin thoroughly with soap and water, then rinse with distilled water
Leeches don’t like strong odours or tastes that may be present (chlorine, antiseptics, barrier creams etc)

Place a dampened square of gauze (with 1cm hole in the middle) on area to be treated.
To prevent the leech from wandering off!

Choose a hungry leech (small active one!) and direct head of the leech to the hole in the gauze.
The leech’s head is the “searching” end!
Attachment generally occurs quickly. If not, produce a tiny droplet of blood with a needle prick

LEECH SUPERVISION
Once attached, the leech usually will remain in place until fully distended (30-60 mins). Check continuously!
If blood flow is poor, leech may detach prematurely and try to find a better site!

Once fed, leeches will drop off the skin

Collect in appropriately labeled container (indicating that leech has been used!) and dispose

Question 21

how to deal with used leeches

Answer 21

Used leeches should be sedated with 8% alcohol before being killed with 70% alcohol for 5 minutes

Killed leeches then can be discarded via a sluice or incinerator.

A leech must NEVER be re-used on a second patient

A used leech should NEVER never be returned to a pharmacy.

Question 21

how to deal with used leeches

Answer 21

Used leeches should be sedated with 8% alcohol before being killed with 70% alcohol for 5 minutes

Killed leeches then can be discarded via a sluice or incinerator.

A leech must NEVER be re-used on a second patient

A used leech should NEVER never be returned to a pharmacy.

Question 22

what is Post-wound care

Answer 22

Each bite must be encouraged to bleed by the gentle removal of any locally forming clot at regular intervals.

Area around leech bite wounds should be routinely observed for local infection (swab if indicated).

If bleeding is severely prolonged, haemoglobin levels should be checked daily.
Significant falls in Hg levels can occur.

Question 23

what are saftey considerations with leeches?

Answer 23

Infection is the main complication
Delayed infection (2-3 days after treatment) has been reported
Leeches are not sterile!
Leech gut contains endosymbiotic bacterium Aeromonas hydrophila (essential for the leech survival).
Aeromonas hydrophila is not normally a bacterial pathogen but may prove pathogenic in certain circumstances
Aeromonas hydrophila infections are easily treated with antibiotics

One case of leech allergy has been reported (not typical)

Question 24

what are contra-indications for leeches

Answer 24

Arterial insufficiency
Grafts vulnerable to infection and leeches are not sterile!
Aeromonas hydrophila may prove pathogenic in tissues compromised by arterial insufficiency
Consider risks vs. benefit.