Bari M.S.¹, Choudhury M.I.M.²,Khan A.-A.-R.³, Nessa A.⁴

¹Department of Plastic Surgery, Sir Salimullah Medical College and Mitford Hospital, Dhaka, Bangladesh
²Surgery Unit 1, Dhaka Medical College Hospital, Dhaka
³City Hospital (Pvt) Ltd, Dhaka
⁴Division of Food and Radiation Biology, Atomic Energy Commission, Savar, Dhaka

SUMMARY. This is a prospective study of 40 patients with deep and deep dermal burns in which human foetal membranes (FMs) - also known as amniotic membrane - were used. FMs were used in 25 patients unsuitable for early burn excision who presented some degree of infection. The results with respect to the formation of granulation tissue were excellent, and the control of infection was satisfactory. FMs were also used in 15 patients over widely meshed split-skin grafts where the formation of hypertrophic granulation tissue through the windows of the mesh-graft prevented coalescence of the epithelium and delayed healing. In five patients in this second group, FMs were used in the split-skin graft donor area. The patients complained of severe pain and dryness in the area, which was relieved by using a moistening ointment.

Introduction

The treatment of major burns is complex and challenging for plastic surgeons throughout the world. Initial treatment starts with resuscitation of the patient to overcome hypovolaemic shock. A large quantity of fluid and electrolytes comes out of the body. Most of the fluid comes out during the first 24 h and to a lesser degree during the second 24 h.

The next step is to take care of the burn wound. Burned skin not only loses its normal function but also gradually disintegrates and provides media for bacterial colonization. Toxin is absorbed from burned tissue and causes adult respiratory distress syndrome, septicaemic shock, and renal failure, and ultimately the patient dies of the multi-organ dysfunction syndrome. Wound care is therefore important.

Wound care can be performed by either the open or the closed method. In the open method, after being cleaned the patient remains in a room with a sterile environment where laminar-flow filtered air and barrier nursing are strictly maintained. It is however in practice impossible to achieve an environment that is absolutely free of micro-organisms, and the closed method of wound care is now popular throughout the world. In this method, after being cleaned the wound is covered with an antimicrobial agent and then wrapped in thick cotton wool and gauze. The dressing is changed at regular intervals.

Recently there have been great developments in wound care, with allografts, amniotic membranes, artificial dermis, and synthetic and semi-synthetic dressing materials playing an important role. In superficial burns, amniotic membrane adheres after application and remains so until epithelialization is complete (Figs. 1a,b). In deep and deep dermal burns, the burned tissue needs to be removed by total burn excision or tangential excision, and the wound is covered with an autograft. At the same time, in burn patients who are not suitable for early excision, the raw surface is covered with an allograft, amniotic membrane, or other dressing material in order to prevent external contamination, with loss of fluid and electrolytes. At a later stage the allograft and the amniotic membrane need to be replaced by an autograft.

Human foetal membrane was first used as a biological skin substitute or dressing about 90 years ago.1 FMs are also known as amniotic membrane.2 Anatomically, FMs consist of two loosely connected layers, an inner one of amnion and an outer one of chorion. The inner amnion layer is composed of cuboidal, flattened epithelial cells and mesenchymal connective tissue. The outer chorion is composed of fairly thick transitional epithelium. Amnion is thin and shiny in contrast to chorion, which is less homogeneous and dull.3 Foetal membrane can be used in toto (amnion + chorion) or only as amnion (epithelium + base membrane).4 Amniotic membrane is also comparable with honey, for its good healing effect.5

Basic properties of human foetal membranes

1. Absence of immunological rejection
2. The healing effects of FMs may be due to:
   • Antibacterial factors
   • Angiogenetic or other biological factors
   • The biomechanical characteristics of FMs

Materials and method

During the period July 2000-June 2001, 40 patients with deep dermal and deep burns were studied in the City Hospital (Pvt.) Ltd, Dhaka, Bangladesh. Human foetal membranes2 were used to cover the burn wound in 25 cases; they were also used to cover widely meshed skin grafts over freshly excised wounds in 15 cases and skin graft donor areas in five cases.

Basic technique

Human FMs were supplied by the Institute of Food and Radiation Biology Division, Bangladesh Atomic Energy Commission, Savar, Dhaka. The FMs are collected in fresh condition from healthy mothers. After being cleaned, the FMs were dried in an oven at 40 ± 2 °C overnight and then sterilized by gamma radiation at 25 KGY.6

The patients were divided into two groups, A and B (Table II).

Group A. Burn patients who were not suitable for early burn excision and were admitted with some degree of infection were the cases selected for application of human foetal membrane (Figs. 2a,b). The burn extent was 10-36%, with a mean burn of 22% (Table I). During every dressing, part of the loose slough was excised and covered with FMs. Every alternate day, the dressing was changed and part of the loose eschar was excised and covered with FMs. These processes continued until all the eschar was removed and covered with an autograft. At the same time the progress of granulation tissue formation was followed. Once healthy granulation tissue formed, the wound was covered with meshed split-skin graft.

Group B. These patients were admitted early and underwent early burn excision, the wound being covered with 1:3 or 1:6 meshed split-skin graft. This meshed skin graft was covered with FMs (Figs. 3a,b).

In five patients in group B, the split-skin donor area was covered with human FMs (Table IIIa) (Fig. 4).

Results

Group A. The formation of granulation tissue was quick, i.e. from 7 to 12 days (average, 8.7 days) from the time of first application (Table IIIb). The wounds in ten patients were grossly infected but the infection was controlled within 7-10 days after application of the FMs (Table IIIb).

Group B. In 15 cases FMs were used to cover meshed split-skin graft. There was hypertrophic granulation tissue through the window of the mesh graft, which prevented coalescence of the epithelium of the mesh graft and delayed healing (Table IIIc).

The split-skin donor area was covered with FMs or amniotic membrane in five patients who complained of severe pain and dryness in the donor area. This pain was relieved temporarily with analgesics and definitively by the application of ointment to keep the wound moist.

Discussion

Reviewing the available literature concerning the utilization of amniotic membrane in the treatment of various skin defects, mainly superficial burns, we have found positive results. The first use of amniotic membrane was reported by Sabella in 1913,1 while in 1952 Douglas reported on its use after extensive flame burns.7 The indications ranged from donor sites (Quinby et al., 1982;8 Robson, 1973; Waikakul et al., 1960) to clean second-degree burns (Pigeon, 1960). FMs have also been successfully used in cases of eye surgery to prevent adhesion and in reconstruction in gynaecological, neurological, urological and vascular diseases.3

The current consensus is that the intimate adherent property of the biological dressing to an open wound in some way suppresses bacterial proliferation and helps to eliminate existing bacteria.9 A number of factors may contribute to this effect. In a clean surgical wound, the collagen of the graft or biological dressing, via its haemostatic properties, will help to stop bleeding and thus prevent subsequent haematomas, which would provide opportunities for bacterial proliferation. In addition, the very close bonding between graft and wound eliminates dead space in which serous exudates could collect and encourage bacterial growth.10 When wounds are contaminated, grafts or biological dressings can not only suppress bacterial growth but also reduce the existing microbial population density.11 A likely explanation for this phenomenon is the bonding of the graft to the wound bed by fibrin: the bacteria are trapped in the thin fibrin matrix linking the collagen fibres of the graft with the collagen of the wound bed. The fibrin matrix provides an ideal substratum for migration of phagocytes and ensures that all the bacteria are within reach of the phagocytes.10

The overall results of this study of the effects of amniotic membrane or FM treatment are as follows:

• deep burns: FMs or amniotic membrane help in wound debridement, reduce wound infection, and contribute to the rapid formation of granulation tissue;
• patients with widely meshed split-skin grafts: hypertrophic granulation tissue through the window of the mesh graft hinders coalescence of the epithelium and delays healing. This also favours rapid angiogenesis;
• split-skin donor areas: patients complain of severe pain. This may be due to dryness resulting from irritation of nerve endings.

Conclusion

The beneficial effects of amniotic membrane or foetal membranes are encouraging, mainly from the point of view of cost-effectiveness and the possibility of their use in countries where cadaver allografts are difficult to procure and pigskin is restricted.

RESUME. Les Auteurs ont conduit une étude prospective de 40 patients atteints de brûlures profondes et de brûlures dermiques profondes traités avec l’emploi de membranes fœtales humaines (MF), appelées aussi membranes amniotiques. Les MF ont été utilisées dans 25 patients non indiqués pour l’excision précoce des brûlures qui présentaient un certain degré d’infection. Les résultats pour ce qui concerne la formation du tissu de granulation étaient excellents, et le contrôle de l’infection était satisfaisant. Les MF ont aussi été utilisées dans 15 patients sur des greffes à épaisseur variable aux mailles larges où la formation du tissu de granulation hypertrophique à travers les fenêtres de la greffe à maille prévenait la coalescence de l’épithélium et retardait la guérison. Dans cinq patients inclus dans ce groupe, les MF ont été utilisées dans la zone donatrice de la greffe à épaisseur variable. Les patients ont souffert de douleurs sévères et de sécheresse dans cette zone,traitées avec un onguent humidifiant.

Bibliography

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