Keywords burn - deep - children - homograft - radiotherapy - rejection
Introduction
Extensive burns destroy the skin,[1 ]
[2 ] lead to the release of proinflammatory mediators at the injury site,[3 ]
[4 ] and cause the malfunction of microcirculation.[5 ]
[6 ] These systemic changes can affect multiple organs in the body[4 ] in a reciprocating manner.[5 ] Approximately 45.3% of burn patients develop multiple-organ dysfunction, which is
the leading cause of death in children.[6 ]
Some limitations restrict the use of autografts with escharectomy for children, such
as an unstable sensitive condition, a small body surface area, and difficulty in determining
the depth of chemical and electrical burns.[7 ] An ideal skin substitute should mimic normal skin functions while causing fewer
reactions.[8 ] The skin is protected by a large number of tissue-resident memory T-cells, which
are recognized by the immune system and initiate antigen-antibody reactions.[9 ] Circulating T-cells infiltrate inflammatory sites and produce epithelial immunity
with local antigen presentation.[10 ] As a result, to use skin homografts as a long-term substitute,[11 ] multiple methods for delaying rejection have evolved, either through systemic or
local procedures, in order to minimize inflammatory and immune reactions.[12 ]
In this study, we assess the ability of radiotherapy to minimize acute rejection and
enhance wound healing in children with deep burns, using skin homografts from related
living donors. Radiotherapy can weaken the skin cells' ability to produce immune and
inflammatory reactions, thereby avoiding the complications of systemic immunosuppressive
drugs.
Patients and Methods
We conducted this prospective randomized controlled trial on 34 children (age: below
12 years) who were admitted to our burn unit between January 2018 and May 2020. On
admission, the total body surface area of the burn was calculated using Lund and Browder's
chart, and the patients received resuscitation treatment, including airway securing,
fluid replacement, warming, and supportive medication, until their general condition
stabilized. Local burn care was routinely provided while adhering to aseptic precautions.
Inclusion and Exclusion Criteria
The inclusion criteria of this study were as follows: children with intermediate,
major, and deep second- and third-degree burns with eschar formation, necessitating
escharectomy and wound coverage.
The exclusion criteria of this study were as follows: children with first-degree and
superficial burns that appeared to be healing conservatively without requiring surgical
intervention.
Study Groups
This study had the following two patient groups:
Group 1 (control, nonexposed) included 17 patients with a skin homograft that was
not exposed to radiotherapy.
Group 2 (case, exposed) included 17 patients in which the skin homograft was exposed
to local radiotherapy (single, low dose of 500 centigray [cGy]) before application
to the burn wound.
Homograft Source and Preparation
Patients in both the groups received skin homografts from living first-degree relatives
(i.e., father, mother, brother, or sister). All donors provided written consent to
donate their skin after a thorough discussion on all procedural steps and the anticipated
time for donor site healing. The thigh was the preferred donor site for homografts,
and medium-sized split-thickness grafts were harvested and applied on a sterile glass
plate soaked with gentamicin solution ([Fig. 1 ]).
Fig. 1 Homograft preparation. (A ) The graft was harvested from the thigh donor site with medium-sized split thickness.
(B ) Meshing of graft and socking by garamycin ampoule.
Local Radiotherapy
Inside the tomotherapy unit for radiation, a calibrated dosimetric system consisting
of an electrometer and an ionization chamber (M23332, Safe Work Permit process) was
used. Beams were delivered using an automated system that moved the phantom at an
11 cm2 pencil beam in a homogenous-slice rotating attitude ([Fig. 2 ]). The skin homograft was exposed to a low dose of radiation, 500 cGy, and the delivery
process was replicated only once on the graft. The homograft was immediately used
for the coverage of a prepared bed after irradiation was completed.
Fig. 2 Irradiation device. (A ) The tomotherapy device with a calibrated dosimetric system, consisting of an electrometer
and an ionization chamber (M23332, PTW). (B ) The beams moving a phantom at a 1 × 1 cm2 pencil beam in homogenous slice-rotate attitude by means of an automated system.
Operative Procedures for Recipient Patients
Under general anesthesia, the burn area was sterilized and escharectomy was performed,
followed by immediate wound coverage with a nonexposed skin homograft for patients
in group 1 or an irradiated homograft for patients in group 2. Next, fixation was
performed with bulking dressing and tie-over sutures.
Follow-Up
To detect differences in the results between the two groups, the following data were
collected before and after surgery and compared:
Laboratory parameters such as the levels of C-reactive protein (CRP), erythrocyte
sedimentation rate (ESR), interleukin 6 (IL-6), and tumor necrosis factor (TNF) were
measured.
Time elapsed between homograft coverage and the onset of rejection.
Percentage of the area requiring an autograft application.
Statistical Analysis
To evaluate the differences between the two groups, we measured various parameters
using one-way analysis of variance and posthoc Tukey's honest significant difference
test. For statistical analyses, we used the Prism 5 software (GraphPad Software, San
Diego, CA USA). We considered p < 0.001 as highly statistically significant and p < 0.05 as statistically significant.
Results
Group 1consisted of 17 patients (6 females and 11 males) with a mean age of 8.33 years
(range: 1–12 years) and a mean percentage of burns of 32.2%. Group 2 included 17 patients
(4 females and 13 males) with a mean age of 9.5 years (range: 2–12 years) and a mean
percentage of burns of 28.37%.
The average percentage of homografts harvested from donors was 8.9% (range: 7.5–9.0%),
with a 10.6-day healing period (range: 8–13 days). Donor site complications included
delayed wound healing in two cases, wound infection, and hyperpigmentation in one
case, all of which were treated conservatively.
The mean values of the laboratory parameters (ESR, CRP, IL-6, and TNF) for all burn
patients in the study showed a significant difference, with p < 0.001 ([Table 1 ]). This finding demonstrates a significant decrease in values for graft radiotherapy,
indicating minimal inflammatory and immune reactions.
Table 1
Changes in the level of the following laboratory parameters including ESR, CRP, IL-6,
and TNF before and after the surgery
Group I homograft not exposed to radiation
n = 17
Group II exposed homograft to local radiation
n = 17
T test
p -Value
Mean ± SD
Mean ± SD
ESR/mm/hr
Before surgery
49.437 ± 11.684
43.333 ± 10.543
2.853
> 0.05
After surgery
38.633 ± 4.819
13.543 ± 4.879
11.808
0.001
p
-Value
< 0.05
0.001>
CRP mg/dl
Before surgery
51.617 ± 6.491
53.637 ± 5.381
3.906
> 0.05
After surgery
38.143 ± 6.62
11.100 ± 3.632
13.341
0.001 >
p
-Value
< 0.05
0.001>
IL-6
Before surgery
111.55 ± 55.114
120.82 ± 70.14
1.675
> 0.05
After surgery
68.550 ± 48.43
18.47 ± 30.35
.987
0.001 >
p
-Value
< 0.05
0.001>
TNF
Before surgery
44.87 ± 15.55
39.64 ± 9.55
3.67
> 0.05
After surgery
33.80 ± 8.56
18.832 ± 7.62
1.80
0.001>
p
-Value
< 0.05
0.001>
Abbreviations: CRP, C-reactive protein; ESR, erythrocyte sedimentation rate; IL-6,
interleukin-6; SD, standard deviation; TNF, tumor necrosis factor.
The mean ± standard deviation (SD) of the time from homograft coverage to the appearance
of rejection was 9.62 ± 1.45 in group 1 and 14.35 ± 2.8 in group 2, with p < 0.001 (highly significant difference), indicating that exposure to radiotherapy
can reduce graft rejection.
The number of patients who required an additional autograft application was 15 in
group 1 (84.6%) and 13 in group 2 (63.6%), with p > 0.05 (nonsignificant). The mean ± SD of the area requiring graft application was
88.5 ± 14.33 in group 1 and 62.7 ± 12.55 in group 2 (highly significant), indicating
a significant effect of the irradiated homograft on decreasing the burn areas requiring
a graft and also decreasing the percentage of graft taken from the patient with a
good stability and fewer complications.
We found a difference in hospital stay duration between groups 1 and 2, with a mean
of 31.3 and 21.0 days, respectively. Irradiation reduces immune reactions and the
possibility of eschar tissue formation, resulting in the acceleration of wound epithelialization
which reduces hospital stay duration and morbidity ([Table 2 ]).
Table 2
The statistical difference between two groups regarding clinical outcomes
Group I
n = 17
Mean ± SD
Group II
n = 17
Mean ± SD
Test
p -Value
Hospital stay duration
(Mean ± SD)
31.3 ± 5.09
21.0 ± 6.05
T = 8.341
< 0.001
Patients number that needs another autograft:
X2 = 1.097
> 0.05
Yes
15 (84.6%)
13 (63.6%)
No
2 (15,4%)
4 (36,4%)
The period from homograft coverage to rejection started (mean ± SD)
9.62 ± 1.45
14.35 ± 2.8
T = 7.901
< 0.001
Percentage of the area need autograft application (mean ± SD)
88.5 ± 14.33
62.7 ± 12.55
T = 10.897
< 0.001
Abbreviations: SD, standard deviation.
Discussion
Many children with deep burns die because of a lack of autologous skin; thus, quick
application of skin substitutes with minimal immune and inflammatory reactions is
a major concern. Homografts are commonly used for coverage of raw burned areas.
No legal issues exist for the use of cadaveric skin grafts in developing countries
that have limited skin-banking equipment. In this study, we used skin homografts harvested
from living first-degree relatives with exposure to radiation therapy for inhibiting
the ability of skin cell recognition, in order to stimulate the immune system, thereby
reducing graft rejection and enhancing epithelialization. This method allows local
exposure while avoiding systemic side effects and complications associated with immunosuppressive
drugs.
Bhatia et al[13 ] used homografts for neonates with burns with no donor sites and achieved satisfactory
results. Although systemic immunosuppressive drugs can reduce rejection of organ transplants,
such as kidneys, they have little or no effects on skin transplantation.[11 ] Better healing and epithelialization occurs when the homograft rejection process
is reduced by minimizing the immune system response.[14 ]
According to Cheuk et al, topical suppression of epidermal memory cells can inhibit
episodes of inflammation in certain dermatological diseases.[15 ] Sterilization of grafts by irradiation is widely used and can provide less-expensive
materials for treatment.[16 ]
[17 ] Camacho and Guerrero recognized chemical and physical changes that influence the
biological properties of a graft after exposure to radiation as a method of sterilization.[18 ] Mahdavi-Mazdeh et al discovered significant results from clinical evaluations of
patients with deep skin burns in whom homografts were exposed to a 25 kGy dose of
radiation.[19 ]
In our study, we used a tomotherapy device to deliver a 500 cGy radiation to a skin
homograft in a single exposure. We found a significant difference in the results with
an irradiated homograft in terms of percentage of rejection, healing, and need for
autografting ([Figs. 3 ], [4 ], and [5 ]).
Fig. 3 Female patient, 4 years old, with scald deep dermal burn. (A ) Early escharectomy and coverage with nonirradiated skin homograft from father was
done. The chest show area of epithelization and healing after 13 days from coverage.
(B ) Rejection of homograft was completed after 15 days from homograft coverage with
a ready granulated bed for autograft replacement. The percentage of rejection was
about 80% of burned area.
Fig. 4 Male patient, 8 years old, with deep dermal scald burn covered by gamma-irradiated
homograft from father. (A ) The allergic signs of rejection as cyanosed of skin undersurface started to appear
after 15 days from coverage with delayed and minimal reactions. (B ) Healing of burned area under irradiated homograft surface was observed after 19
days from coverage.
Fig. 5 Female patient, 2.5 years old, with deep dermal scald burn covered by irradiated
homograft from father. (A ) Eschar tissues all over the burned areas on the fourth day of injury. (B ) The signs of rejection as skin discoloration and redness with granulation under
surface burn areas. (C ) Healing of burned area after complete homograft rejection at day 14 from coverage.
According to Naoum et al, homograft application for extensive burns can improve patient
outcomes while reducing length of hospital stay.[20 ] Khoo et al concluded that burn coverage with homografts can promote angiogenesis
with enhanced capillary ingrowth, provide growth factors and cytokines that cause
chemotaxis and proliferation as a part of the inoculation process, and act similarly
to an autologous skin graft. This incorporation occurs at the dermal collagenous matrix
level.[3 ]
Local radiotherapy of the skin homograft reduces its ability to initiate immunological
and inflammatory reactions, resulting in less inflammation and facilitating insidious
creeping replacement of the homograft epidermis by native epithelium. In our study,
the most significant fluctuation in the levels of laboratory parameters, including
ESR, CRP, IL-6, and TNF, showed a significant decrease with the application of an
irradiated homograft. Thus, we can assume that these parameters can be used as tools
to predict the results and prognosis of such a treatment.
Our study has some limitations, including the large number of variables with a small
number of patients. As a result, we were not able to develop a solid prognostic index.
Thus, further studies of changes occurring in the immunological and inflammatory mediators
of burn patients during management are required.
Conclusions
The exposure of skin homografts from related living donors to a local low dose of
radiotherapy can reduce a graft's ability to initiate inflammatory and immunological
reactions, thereby minimizing rejection of a graft and enhancing epithelialization
in children with deep second- and third-degree burns. More multicenter studies are
needed in the future to recommend this technique as a safe routine procedure.
