Annals of Burns and Fire Disasters - vol. XI - n. 1 - March 1998

KERATINOCYTES AS BIOLOGICAL DRESSING IN THE TREATMENT OF PARTIAL-THICKNESS BURNS IN CHIILDREN

Dédovic Z.*, Koupilovià I.**, Suchànek V.*

*Burn Centre, Bohunice Teaching Hospital, Masaryk University, Brno, Czech Republic
**Department of Social Medicine, Faculty of Medicine, Masaryk University, Brno

SUMMARY. In order to evaluate the treatment of deep dermal burns with keratinocytes and to establish the possibility of reducing hospitalization and the frequency of painful wound rebandaging, a survey is presented of 109 children with deep dermal burns treated with cultured epidermal allografts. The decline in the mean duration of hospitalization was statistically significant compared with that of children treated without the use of keratinocytes. The healing of deep dermal burns treated with keratinocytes was successful in all patients, in accordance with our expectations. The application of these biological allografts had to be repeated - twice at most - in only in 24.7% of cases.

A retrospective review was made of all children with partial-thickness burns admitted to the burn centre in Brno (Czech Republic) from 1992 to 1995 and treated with cultured epidermal allografts. Since 1992 keratinocytes have been used routinely as a biological dressing in the treatment of burn wounds. This method of mobilizing the body's own healing potential for deep dermal burns has become an important tool in the treatment of children's burns. As the treatment of full-thickness burns with cultured epidermal allografts or autografts proved unsuccessful, we focused on the use of keratinocytes in the treatment of partial-thickness burns only. In the period in question, an annual average 125 children were hospitalized in our burn centre; 50% of these were in the most vulnerable age group between 0 and 3 yr of age.

Almost 80% of the children hospitalized were scalded. The aim of the present study was to evaluate the use of keratinocytes as a biological dressing in order to reduce the period of hospitalization, especially that of young children, who constitute a particularly traumatized group exposed to psychological and physical stress in the event of prolonged hospitalization.

Patients and methods

From October 1992 to 31 December 1995 we hospitalized 109 burned children between 0 and 14 yr of age treated with cultured epidermal allografts. We investigated separately children with deep dermal burns (Figs. 1, 2) and those with mixed burns (partial-thickness and full-thickness) (Figs.3,4). The characteristics of these groups were compared with 60 children admitted to our Centre in 199 1, when the method of keratinocyte treatment had not yet been introduced

Fig. 2 - Partial-thickness burn after removal of keratinocytes (same .patient as Fig. 1). Fig. 3 - Application of keratinocytes in portion of partial-thickness burn in patient with extensive mixed burns. Fig. 4 - Healing of part of partial-thickness burn after removal of keratinocytes (same patient as Fig. 1).

The preparation of keratinocytes was performed according to standard routine and protocol. The most commonly used area for the harvesting of viable keratinocytes is the skin of the posterior side of auricles obtained during the surgical procedure of otoplasty in children aged 6 to 12 yr. The total duration of the growth of cultured epidermal keratinocytes was most frequently 20 days. The culture was grown using a slightly modified Rheinwald-Green technique. The cultured epidermal grafts were in the form of a multilayer of two to nine layers fixed on to the carrier as a substitute for its own missing keratinocytes at the surface of partial-thickness burns. The preparation of the wound bed for the application of keratinocytes was of decisive importance for the outcome of the whole procedure. The wound bed had to be clean, well vascularized, free from necrotic tissue residues, and with a minimum of contamination. Because of this, keratinocyte treatment was started comparatively late after the treatment with 1% silver sulphadiazine, which supported the debridemerit and healed the surrounding superficial burns. After a 24 h intermission without antiseptics or silver sulphadiazine, the wound bed was ready for keratinocyte treatment. The dressing was changed for the first time 48 h after application of the graft, when it had already adhered to the surface of the wound and the carrier was easy to remove.

The characteristics of patients treated and not treated with cultured epidermal allografts can be seen in Table I. The duration of hospitalization in patients with second-degree burns ranged from 7 to 37 days in 1991 and from 6 to 30 days in 1992-95, respectively.

The mean duration of hospitalization was 17 days in 1991, dropping to 13.1 days in 1992-1995. The decline in the mean length of hospitalization of patients with partial-thickness burns was almost four days, which was statistically very significant (difference for 11 degree: 3.9 [95 % Cl 2.0, 5.91 days =p < 0. 00 1) (Table II).

The length of hospitalization in patients with mixed second- and third-degree burns ranged from 24 to 58 days in 1991 and from 10 to 68 days in 1992-95. The mean length of hospitalization dropped from 34.4 days in 1991 to 28.6 days in 1992-95, but the difference was not statistically significant (difference for 11 + III degree: 5.8 [95% Cl -2.9, 14.51 days p = 0.188). It should be noted that we treated only the deep dermal portions of mixed burns.
Table III shows that the treatment of patients with cultured epidermal grafts from 1992 to 1995 was successful in all 73 children with partial-thickness burns only.

The proportion of successfully treated deep dermal burns in patients with partial- and full-thickness burns was 77.8% in our sample. In eight patients with mixed burns, autografting had to be performed in the area treated unsuccessfully with keratinocytes. This was due either to erroneous estimation of burn depth or to possible contamination of the wound. In 24.7 % of children with partial-thickness burns, application of keratinocytes was repeated twice at most (Table IV). The difference in the proportion of autografts performed in children with partial-thickness burns and in those with mixed burns was statistically highly significant.

Table V shows that the period of grafting ranged from 3 to 18 days in patients with partial-thickness burns and from 4 to 28 days in those with mixed burns. The average period of grafting was 9.8 days in children with only partial-thickness burns and 13.2 days in those with mixed burns. The grafting in patients with more complicated injuries (mixed burns) was thus performed 3.4 days later on average, a difference that was statistically highly significant (difference 3.4 [95% CI 1.9, 4.81 days p < 0.001).

The success of treatment in children treated with keratinocytes according to the day of grafting is shown in Table VI. Looking at the relationship between the time of grafting and the success of treatment in the group of patients with mixed burns, we found in our sample that successful keratinocyte treatment did not depend on the time of application. There was no statistically significant difference in linear trend in the proportion of successfully treated patients in the three categories of grafting time.

Keratinocytes isolated from small skin biopsies and cultured according to the Rheinwald-Green technique' are able to undergo rapid expansion in vitro and may be regarded as a form of biological dressing in deep dermal burn.
The aim of our study was to determine the effectiveness of using keratinocytes in the treatment of partial-thickness burns.' Keratinocyte treatment presents both advantages and limitations in its use. Our results show that the treatment of children with partial -thickness burns was relatively successful in our burn centre between 1992 and 1995. In addition to other advantages of this particular treatment strategy, a significant decrease was observed in the average length of hospitalization. The humaneness of this method also consists in the immediate pain relief and the reduction in the number of painful wound dressings, a matter of cardinal importance for children who are exposed to the extreme physical suffering and psychic stress induced by hospitalization.9 In patients with both partial and full-thickness burns keratinocyte treatment was successful in more than three-quarters of our patients. The failure of the method in the other patients in this group could well be explained by the immediate vicinity of full-thickness burns and contaminated necrectomized areas.
With regard to limitations in their use, the application of keratinocytes is not suitable in certain body areas. In our experience, the back, neck, and certain parts of the head are not the preferred areas, because dressings in these body sectors are rather difficult to apply and grafts are more susceptible to the mechanical loss of cultured human keratinocytes than are routine autografts." The arms, legs and the anterior trunk are preferable sites of coverage." Some authors recommend the application of splints for limbs in patients with cultured epidermal grafts, thus avoiding pressure in the areas treated. Silver-containing local antiseptics (sulphadiazine silver, silver nitrate) cause moderate inhibition of growth. The cost of keratinocyte treatment is high but so far no optimal, safe and inexpensive method of wound bed preparatioln and of healing deep dermal burns has been found.

RESUME. Les Auteurs, dans le but d'évaluer le traitement de brûlures thermiques profondes moyennant les kératinocytes et de trouver des modalités pour abbrévier l'hospitalisation et réduire le numéro des procédures douloureuses des médications, présentent les résultats d'une étude sur 105 enfants brûlés atteints de brûlures dermiques profondes traitées avec des allogreffes épideriniques cultivées. La réduction de la durée moyenne de l'hospitalisation a été statistiquement significative par rapport au traitement des enfants traités sans l'emploi des kératinocytes. La guérison des brûlures dermiques profondes traitées avec les kératinocytes s'est démontrée un succès dans tous les patients, selon les prévisions des Auteurs, et il a été nécessaire de répéter l'application de ces allographes biologiques seulement dans 24,7 des cas.

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