Interactions between local and generalised burn edema

Erythropoietin in the prevention of experimental burn progression

Background

Damage control is essential in first aid of burn lesions. The aim of the present study was to investigate whether systemic erythropoietin (EPO) administration could prevent secondary burn progression in an experimental model.

Methods

The burn comb model creates four rectangular burn surfaces intercalated by three unburned zones prone to progression. Twenty-one Wistar rats were randomized to a control group or to receive intraperitoneal EPO (500 units per kg) once a day for 5 days starting 45 min (EPO45min) or 6 h (EPO6h) after burn injury. Histological analyses assessing burn depth, inflammation and neoangiogenesis, planimetric evaluation of burn progression, and laser Doppler flowmetry to assess perfusion were performed after 1, 4 and 7 days. Final scarring time and contracture rate were assessed once a week.

Results

Burn progression was decreased significantly with EPO45min but not EPO6h; progression of burn depth stopped in the intermediate dermis (mean(s.e.m.) burn depth score 3·3(0·6) for EPO45min versus 4·7(0·3) and 5·0(0·0) for EPO6h and control respectively on day 7; P = 0·026) and the surface extension was significantly reduced (45(8), 65(4) and 78(4) respectively on day 7; P = 0·017). This was paralleled by faster re-establishment of perfusion with EPO45min (114(5) per cent on day 4 versus 85(6) and 91(3) per cent for EPO6h and control respectively; P = 0·096). The reduction in progression resulted in a decreased healing time (7·3(0·7) weeks for EPO45min versus 11·5(1·0) and 10·8(0·5) weeks for EPO6h and control; P = 0·020) and contracture rate (P = 0·024).

Conclusion

Early EPO prevented burn progression, mainly by improved vascular perfusion.

Is HBOT treatment effective in recovering zone of stasis? An experimental immunohistochemical study

Studies aimed at recovering the zone of stasis are one of the major issues of experimental burn studies. Hypoxia and oedema at that zone may cause irreversible changes. Due to anti-oedematous and antihypoxic effects of hyperbaric oxygen treatment (HBOT), it may be beneficial in recovering the zone of stasis. We performed an experimental study using 20 Sprague-Dawley rats, each weighing 350-450 g. The rats were first divided into two groups as 24h and 5 days. Subsequently, control and treatment groups (five rats in each group) were formed. For burn wounds, we used the burn comb model, which was described by Regas and Ehrlich. In the treatment group, 2.5 ATA HBOT was applied for 90 min twice daily. A 0.8-cm punch biopsy was performed and samples for histological examination were taken from the centre of burn area. The rats were sacrificed by administering '3 mci technetium-99m methoxy butyl nitrite' ((99)Tc(m) MIBI) through the femoral vein. Biopsy materials were evaluated by histological and immunohistochemical methods. Dorsal skin fragment, excised to 1cm margin, was imaged by scintigraphic measurements with a gamma camera. Wet and dry weight measurements of excised skin fragments were taken. As a result, HBOT showed a positive effect at the cellular level in the first 24h. It increased recovery potential by augmenting neovascularisation and decreasing oedema in the 5-day group.

Cytotoxicity of topical antimicrobial agents used in burn wounds in Australasia

BACKGROUND

Burn sepsis is a leading cause of mortality and morbidity in patients with major burns. The use of topical antimicrobial agents has helped improve the survival of these patients. Silvazine (Sigma Pharmaceuticals, Melbourne, Australia) (1% silver sulphadiazine and 0.2% chlorhexidine digluconate) is used exclusively in Australasia, and there is no published study on its cytotoxicity. This study compared the relative cytotoxicity of Silvazine with 1% silver sulphadiazine (Flamazine (Smith & Nephew Healthcare, Hull, UK)) and a silver-based dressing (Acticoat (Smith & Nephew Healthcare, Hull, UK)).

METHODS

Dressings were applied to the centre of culture plates that were then seeded with keratinocytes at an estimated 25% confluence. The plates were incubated for 72 h and culture medium and dressings then removed. Toluidine blue was added to stain the remaining keratinocytes. Following removal of the dye, the plates were photographed under standard conditions and these digital images were analysed using image analysis software. Data was analysed using Student's t-test.

RESULTS

In the present study, Silvazine is the most cytotoxic agent. Seventy-two hour exposure to Silvazine in the present study results in almost no keratinocyte survival at all and a highly statistically significant reduction in cell survival relative to control, Acticoat and Flamazine (P<0.001, P<0.01, P<0.01, respectively). Flamazine is associated with a statistically significant reduction in cell numbers relative to control (P<0.05), but is much less cytotoxic than Silvazine (P<0.005).

CONCLUSION

In this in-vitro study comparing Acticoat, Silvazine and Flamazine, Silvazine shows an increased cytotoxic effect, relative to control, Flamazine and Acticoat. An in-vivo study is required to determine whether this effect is carried into the clinical setting.

The influence of the C1-inhibitor BERINERT and the protein-free haemodialysate ACTIHAEMYL20% on the evolution of the depth of scald burns in a porcine model

Standardized deep partial-thickness burns were inflicted on domestic pigs by scalding 30 per cent of the skin surface for 25 s with 75 degrees C hot water. The animals (n = 18; weight 25-35 kg) were divided into three groups: I, control group (n = 6), Ringer's lactate only; II, haemodialysate group (n = 6), Ringer's lactate and a protein-free haemodialysate of calf-blood (ACTIHAEMYL20%; AH) and III, C1-inhibitor group (n = 6), Ringer's lactate and C1-inhibitor (C1-INH; BERINERT). Skin biopsies were taken at defined time points (4, 28, 52 and 76 h) and investigated histologically. Depth of burn was determined morphometrically after coloration with a modified MTT-staining on frozen sections of the skin biopsies. Fluid therapy with C1-INH decelerated significantly the progression of the burn wound in the postburn-period compared to Ringer's lactate alone. In comparison with C1-INH, the treatment with AH demonstrated a less beneficial influence on the depth of scald burns. The favourable effects of C1-INH are explained by the protection of the dermal microcirculation during the acute phase of thermal injury.

Reduction of progressive burn injury by a stable prostaglandin I2 analogue, beraprost sodium (Procylin): an experimental study in rats

Beraprost sodium is a chemically stable prostaglandin I2 analogue with antiplatelet and vasodilator actions. Burn injury causes thrombosis and vessel occlusion by increasing the blood viscosity and by thermal damage to the vascular network in the dermis. A vascular response also occurs in the uninjured dermis surrounding the site of injury. Diminished blood flow and spreading tissue oedema lead to progressive ischaemia and necrosis around the burn site (zone of stasis), with the final necrotic tissue area being larger than the initial one. If blood flow could be restored in the zone of stasis, secondary tissue damage would be minimized. In this study, we examined the effects of a prostaglandin I2 analogue, beraprost sodium (Procylin, Kaken Pharmaceutical Company, Tokyo, Japan) on burn injury in rats. Twenty male Sprague-Dawley rats weighing an average of 450 g were burned with a comb-shaped brass probe that produced a row of three burns measuring 10 x 30 mm each and two intervening unburned areas measuring 5 x 30 mm each. The rats were divided into two groups of 10 animals. One group received 0.015 mg of beraprost sodium intraperitoneally immediately after burn injury, while the control group received the same volume of saline. Skin blood flow was measured with a laser Doppler flowmeter, and the development of oedema as well as the area of necrotic tissue were also determined. The extent of skin necrosis and oedema were significantly reduced in the beraprost sodium-treated rats, and blood flow in the zone of stasis was increased. These findings demonstrate that prostaglandin I2 plays an important role in burn injury and that beraprost sodium can reduce secondary necrosis in the zone of stasis.