Biosurgical Products Flashcards
what is the principle of treatment of chronic wounds
Remove necrotic (dead) tissue
Prevent wound infection
Encourage healing
what are conventional treatments for wound care
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
what are alternatives to conventional wound care and what is it?
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)
why is maggots used in clinics
Long history of their clinical use and benefits
how does maggots help with wounds?
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
maggots secretion
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
life cycle of a green bottle fly - breeding cycle.
eggs
larva - 4-7 days
pupa-10-20 days
adult
Production of sterile maggots
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
Production of sterile maggots
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
how are maggots applied?
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)
what might patients notice with maggot treatment
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.
What wounds cannot be treated with maggots?
Dry wounds (but a moist gauze swab may be sufficient to provide moisture)
Wounds in body cavities
Why consider maggot therapy over conventional therapy?
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.
what are Accepted clinical uses of leeches
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.
what are the Benefit of Leeches in Microsurgery
Drain blood from congested sites
Relieve building pressure
Prevent blood clotting in small veins in graft
How do leeches do it?
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!
what are Substances in leech “saliva” and their roles
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
what is hirudin and its role
Potent anti-coagulant in leech saliva
Prevents blood from clotting by binding to and inactivating thrombin, thus inhibiting conversion of fibrinogen to fibrin
what are examples of Leech-derived drugs
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
how do you Care for leeches
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
how can you apply the leeches
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
how to deal with used leeches
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.
how to deal with used leeches
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.
what is Post-wound care
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.
what are saftey considerations with leeches?
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)
what are contra-indications for leeches
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.
