Annals ofBurns and Fire Disasters - vol. IX - n. 2 - June 1996

AMNIOTIC MEMBRANES FOR TEMPORARY BURN COVERAGE

Hadjiiski 0., Anatassov N.

Burn and Plastic Surgery Centre, Pirogov Emergency Medical Institute, Sofia, Bulgaria

SUMMARY. A survey is made of the use of amniotic membrane as a temporary coverage for burn wounds. Amniotic membrane can be used for superficial bums, deep burns, after necrectomy, on extensive granulating wound surfaces, on autografts, in donor regions, and after dermoabrasion. Amniotic membrane is readily available and does not present immunological problems. It does not cause allergic responses and reduces water loss. The risk of the transmission of some viral infections has to be taken into account. Bacterial examinations performed in 20 patients with burn wounds covered with amniotic membrane showed low or no bacterial colonization of the burn surface. It is concluded that amniotic membrane should be more widely used in this particular aspect of burn treatment.

The idea of using a biological dressing in the treatment of extensive burn injuries has been increasingly put into practice in the last 10 to 15 years. The two main reasons for its use are:

• the increasing number of patients with extensive deep burns who survive the acute period of trauma and require complex programmes of plastic reconstructive treatment

• the wide application of necrectomies that leave raw areas of flesh requiring immediate post-operative coverage

Although the ideal temporary coverage has yet to be found, those now available provide good possibilities for burn treatment.

Biological coverages should:

• be adherent to (and grow well on) the burn surface
• maintain low bacterial growth or prevent subsequent bacterial contamination of the injured surface
• reduce the loss of fluids, microelements and proteins from the injured surface
• have good fluid or gas permeability from the wound surface towards the surrounding tissue
• be easy to handle, i.e. when placing on or removing from the injured surface, and also fit closely to incised anatomical regions
• relieve pain, and promote care of the injury
• decrease the possibility of scar or keloid formation during the healing process
• be available. in sufficient quantity and be reasonably priced

Biological dressings have the following disadvantages:

• early graft rejection
• rapid, acute bacterial colonization of the injured area

There are three basic type of temporary biological dressings available:

Biological skin dressings

• Allograft
• Xenograft: bovine, ovine, canine, porcine; cheap and readily available; used fresh, frozen or lyophilized
• Cultured allograft: good results, but quite an expensive method
• Collagen products: gel, sponges or other different plaques
• Amniotic membrane

These have many of the positive characteristics of biological dressings, plus some other features (e.g. industrial production, relatively low price), and include: Opsite, Omiderm and Duoderm.

These are complex compounds of bioagents (collagen), impregnated with silicone nets, such as Biobrane and Armigel. What is the role of amniotic membrane in the topical treatment of burn injuries? Allo- and xenografts possess numerous positive characteristics, but their use is sometimes limited, especially where tissue banks have not been developed. Amniotic membrane has been used since 1912 with variable success as a material for burn injury coverage. It has the following advantages:

• readily available in sufficient quantity
• application not associated with immunological problems
• large size
• simple to prepare and sterilize
• no allergic reactions
• up to 15% reduction of water losses in wounds
• histological structure similar to that of skin

The disadvantage of the use of amniotic membrane is that there is some risk of viral infection transmission, e.g. hepatitis, syphilis and AIDS.
Two varieties of amniotic membrane are mainly used:

• in toto (amnion + chorion) on deep burns
• amnion alone (epithelium + basic membrane) on superficial burns

Fig. la - Superficial bum covered by amniotic membrane. Immediately after accident. Fig. 1b - During treatment. Fig. 1c - The final result Fig. 2a - Nine-year-old boy with deep bum. Immediately after accideni

facial burns
limited superficial burns
open treatment of patients with large burn regions

Method of application: after hospitalization of the patient, fresh burns are appropriately treated and the wound surface is covered with amniotic membrane. A dry dressing is applied for 24 hours, which makes the amniotic membrane adhere to the wound surface. The following day a control dressing is performed, the membrane is changed if necessary, and if already dry, the burn surface remains open until epithelialization is complete.
This method has some definite advantages: no painful dressing changes; no additional bacterial contamination of wounds; reduction of fluid and protein losses from the bums. The granulated burn presents a strong epithelium of good quality.
Throughout the entire course of treatment, 20 patients aged between 1 and 70 years suffering from 1 to 50% 13SA burns presented little or no bacterial colonization of the burn surface. Only three patients showed an increase in the bacterial microbial count; the therapy was changed in two patients (Table I).

Amniotic membrane can be used:

• during preparation of deep burns for necrectomy, to keep necrotic formations dry
• after necrectomies leaving raw areas of flesh - frequently in combination with other temporary biological skin coverages and/or autografts

• on large granulating wound surfaces
• on widely perforated (1:3, IA) autografts

In some of these case, allo- or xeno-grafts can be more effective, but if 1101 available they may he replaced by amniotic membrane.
Compared with patients with superficial burns, in whom amniotic membrane dressing changes are seldom necessary, patients with deep burns require more frequent changes, as the dressings (end to disintegrate. However, the dressings always keep the underlying fiSSLIC and viable, without any sign of local infection, and this helps to promote successful autotransp ants.

These are immediately covered after graft take and haemostasis; the amniotic membrane is left in place until complete epithelialization of the donor region surface.

The surgically prepared SUrfaCC is covered with amniotic membrane, which detaches after healing ofthe abrasive SUffaCC.

Conclusion

1. The positive features of amniotic membrane make it a routine method of burn treatment.
2. Despite more restricted indications for its use in comparison with allo- or xenografts, amniotic membrane has a precise role in the treatment of superficial and deep burns.

3. Amniotic membrane should be used more intensively in burn treatment.

Fig. 2b - Wound surface covered with amniolic membrane after excision. Fig. 2c - The final result.

RESUME. Les auteurs considèrent l'emploi de la membrane amniotique comme couverture provisoire des brûluics. La nieintiranc ainniotique peut être usée pour les brûlures superficielles et profondes, après la nécrectomie, sur les surfaces étendues (le lésions granuleuses,, sur les autogreffes, dans les sites donneurs de peau, et après la dernioabrasion. La membrane amniotique est facilement (li.,,Iionible et ne présente pas de problèmes immunologiques. Elle ne cause pas de réactions allergiques et réduit les pcrte~ hydriqiics~. Il faut lenir compte (lu risque de la transmission de certaines infections virales, Les examens, bactériologiques effectués dans 20 pa1i(,nl,,~ doit( brûlur", étaient couvertes avec la membrane amniotique ont indiqué l'absence ou un bas niveau de colonisation bactérienne (le, la surlace brûlée. Les auteurs concluent qu'il faudrait employer plus diffusément la membrane amniotique pour cet aspect particulier (lit traiteritent des brûlures.

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