ORIGINAL ARTICLE

Treatment of Secondary Burn Wound Progression in Contact Burns—A Systematic Review of Experimental Approaches Daniel Schmauss, MD,* Farid Rezaeian, MD,† Tom Finck, MS,* Hans-Guenther Machens, MD,* Reto Wettstein, MD,‡ Yves Harder, MD*

After a burn injury, superficial partial-thickness burn wounds may progress to deep partialthickness or full-thickness burn wounds, if kept untreated. This phenomenon is called secondary burn wound progression or conversion. Burn wound depth is an important determinant of patient morbidity and mortality. Therefore, reduction or even the prevention of secondary burn wound progression is one goal of the acute care of burned patients. The objective of this study was to review preclinical approaches evaluating therapies to reduce burn wound progression. A systematic review of experimental approaches in animals that aim at reducing or preventing secondary burn wound progression was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta Analysis (PRISMA) guidelines. The selected references consist of all the peer-reviewed studies performed in vivo in animals and review articles published in English, German, Italian, Spanish, or French language relevant to the topic of secondary burn wound progression. We searched MEDLINE, Cochrane Library, and Google Scholar including all the articles published from the beginning of notations to the present. The search was conducted between May 3, 2012 and December 26, 2013. We included 29 experimental studies in this review, investigating agents that maintain or increase local perfusion conditions, as well as agents that exhibit an anti-coagulatory, an anti-inflammatory, or an anti-apoptotic property. Warm water, simvastatin, EPO, or cerium nitrate may represent particularly promising approaches for the translation into clinical use in the near future. This review demonstrates promising experimental approaches that might reduce secondary burn wound progression. Nevertheless, a translation into clinical application needs to confirm the results compiled in experimental animal studies. (J Burn Care Res 2015;36:e176–e189)

In the year 2013, approximately 450,000 people required medical treatment for a burn resulting from thermal, chemical, or electrical injury in the United States.1 Superficial burns usually heal spontaneously under conservative treatment without sequelae. Deep From the *Department of Plastic Surgery and Hand Surgery, Klinikum rechts der Isar, Technische Universität München, Munich, Germany; †Department of Plastic Surgery and Hand Surgery, Universitätsspital Zürich, Switzerland; and ‡Department of Plastic, Reconstructive and Esthetic Surgery, University Hospital Basel, Switzerland. Address Correspondence to Daniel Schmauss, MD, Department of Plastic Surgery and Hand Surgery, Klinikum rechts der Isar, Technische Universität München, Ismaningerstrasse 22, D-81675 Munich, Germany. Copyright © 2014 by the American Burn Association 1559-047X/2014 DOI: 10.1097/BCR.0000000000000131

e176

burns, however, require surgical treatment that consists of escharotomy and tangential excision, followed by one- or two-stage reconstruction using skin-grafts and/or flaps.2–5 Already in 1953, Jackson proposed a classification of the burned tissue into three different zones, ie, the central (core) zone of coagulation surrounded by the zone of stasis characterized by stagnant blood-flow and hypoperfused tissue and the outermost hyperemic zone (Figure 1).6 The core zone is irreversibly damaged beyond repair, whereas the tissue in the hyperemic zone usually recovers without any sequelae. The area of interest is therefore the critically perfused zone of stasis (functionally impaired tissue yet still viable), which will be recruited into the core zone if kept untreated,2,6 as described in ischemic strokes,7 or in

Journal of Burn Care & Research Volume 36, Number 3

Schmauss et al   e177

MEDLINE, Cochrane Library, and Google Scholar by two independent reviewers with the key words “burn wound progression” or “burn conversion” or “wound conversion” or “secondary burn progression” or “zone of stasis” or “stasis zone.” The reference lists of the searched articles were further reviewed for potentially relevant articles. All the relevant manuscripts published in the above mentioned databases from the beginning of notations to present were reviewed. We conducted the search between May 3, 2012 and December 26, 2013. Figure 1.  A cross-section of the skin, subcutaneous tissue, and muscle. The zone of stasis (purple) is surrounding the zone of coagulation (black). The outermost zone is the hyperemic zone (red).

flaps.8 This clinically important phenomenon is called secondary burn wound progression or conversion. The zone of stasis is characterized by blood coagulation, ischemia, and inflammation. Coagulation of the tissue interrupts microcirculation due to direct thermal injury.9,10 Plugging of microvessels surrounding the burned area results from hypercoagulability that usually occurs 2 to 3 hours post-burn.11 Edema formation further aggravates the local perfusion conditions. Oxygenation and energy supply of the tissues become inadequate, metabolic products accumulate and the tissue injury progresses in surface and depth. However, blood flow in the zone of stasis only decreases without immediate tissue necrosis.9 Re-establishment of adequate perfusion conditions and confinement of inflammation is therefore crucial in salvaging the intercalated zone of stasis and so preventing secondary burn wound progression. Although treatment strategies of burn injuries and patient outcome have improved over time, currently there are neither accepted nor standardized therapeutic approaches that prevent secondary burn wound progression in humans.5 Different agents have been used in animal models to rescue the zone of stasis. These agents aim at preventing vasoconstriction, hypercoagulability, and/or inflammation. We reviewed published animal studies aimed at evaluating therapies to reduce secondary burn wound progression.

Eligibility Criteria The inclusion criteria were experimental, in vivo, non-human, manuscripts published in English, German, Italian, Spanish, or French language and targeting treatment strategies that would reduce secondary burn wound progression. Further inclusion criteria were thermal injuries induced by contact burns, evaluation of burn progression in depth using histology and/or in surface using planimetry. It was our aim to present the current status of treatment options in an experimental setting that are potentially transferable into clinic. Studies inducing treatment before burn injury in all the experimental groups were excluded due to unrealistic feasibility in clinical practice. We only included studies in which the burns were induced by contact burns to keep the selection of studies implemented in this review as homogeneous and comparable as possible.

Study Selection The title and/or abstract of citations found through database search and reference screening were reviewed for eligibility. The full-text was retrieved for evaluation of final inclusion into the systematic review.

Data Collection Process Data extraction from the articles included authors, date of publication, experimental-model, treatment-regimen, methods, and results and were listed separately by two independent reviewers (Daniel Schmauss/Tom Finck). The discrepancies were reviewed by all the reviewers and discussed until the consensus was accomplished.

METHODS

RESULTS

The systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta Analysis (PRISMA) guidelines.12 The literature review includes exclusively approaches applied in animals and was conducted in

Literature database search using the predefined keywords revealed 830 articles and abstracts (348 MEDLINE, 82 Cochrane Library, and 400 Google Scholar) (Figure 2). After adding studies identified in the reference lists and removing duplicates,



Journal of Burn Care & Research May/June 2015

e178   Schmauss et al

Studies identified through database searching

Studies identified through reference list

n = 830

n = 10

- MEDLINE = 348 - Cochrane Library = 82 - Google Scholar = 400

Studies after duplicates removes n = 280

Studies screened for more detailed evaluation after reading the title

Studies excluded after reading abstract n = 25

n = 67

Full-text articles assessed for eligibility n = 42 Full-text articles excluded after reading full-text n = 13 - Scald injury = 5 Studies included in the systematic review n = 29

- No data about burn depth or surface progression = 5 - Induction of treatment prior to burn = 3

Figure 2.  Flow diagram: search and selection strategy of included articles.

280 articles were screened by reading the titles of the articles, yielding a total of 67 articles. Of these, 25 articles were excluded after a review of their abstracts, resulting in a total of 42 articles eligible for full-text reading. Out of these 42 articles, 13 studies were excluded (scald injury: n = 5; no data about burn depth or surface progression: n = 5; induction of treatment prior to burn: n = 3). Finally, 29 articles were included (Figure 2). Pathophysiological mechanisms that have been associated with decreased burn wound progression were analyzed, including tissue perfusion, as well as anti-coagulatory, anti-inflammatory, anti-apoptotic, and anti-oxidative effects. Local burns were induced by some form of stamp, most often by the “burn-comb.”9 Tables 1 to 5 provide information for each study, whether analysis of superficial wound progression

(planimetry) and/or deep wound progression (histology) have been performed. In 18 of the 29 studies, both planimetry and histology have been performed to investigate burn wound progression. In the remaining 11 studies only planimetry (n = 5) or histology (n = 6) were available. The column “Follow-up” indicates the length of the study, respectively the last time-point at which histological and/or planimetrical assessment of the burn injury were performed.

Local Perfusion The tissue in the zone of coagulation is directly destroyed by the thermal injury eventually resulting in irreversible tissue necrosis (Table 1).13 Within the zone of stasis, vasoconstriction, edema-formation, and thrombosis of microvessels cause a decrease of perfusion levels. However, this does not at first result

Rat

Rat

Tobalem et al20

Tobalem et al23

Erythropoietin

TAK-044 Cold water (17°C) Warm water (37°C) Erythropoietin

Agent

i.p.

i.p.

i.v. Topical

Mode

After (45 min) After (6 hr)

After (45 min)

After (immediately) After (immediately)

Time

Application

Repetitive

Repetitive

Single Single

Regimen

500 IU/kg bw 2.500 IU/kg bw 500 IU/kg bw

1 mg/kg bw 20 mins

Dosage

11

Rat Rat Rat Rat

Animal

r-tPA Activated protein C Beraprost sodium Poloxamer-188

Agent i.v. i.v. i.p. i.v.

Mode After (2 hr) After (immediately) After (immediately) After (immediately)

Time

Application

Single Continuous (5 hr) Single Repetitive

Regimen

1 mg/kg bw 24 μg/kg/hr 0.015 mg 200 mg/kg bw every 24 hr

Dosage

7 days 5 hr 7 days 3 days

↑ ↓ ↑ n.a.

Perfusion

↑ ↑ ↑↑ ↑ ≈ ↑ ≈

Perfusion

Follow-Up

7 days

7 days

7 days 7 days

Follow-Up ↓ ↓ ↓↓ ↓↓ ↓ ↓ ≈

↓ n.a. ↓ ↓

SWP

SWP

↑ and ↓ indicate significant changes (P < .05). bw, bodyweight; DWP, deep wound progression; i.p., intraperitoneal; i.v., intravenous; n.a., not available; r-tPA, recombinant tissue-type plasminogen activator; SWP, superficial wound progression.

Işik et al Meyerholz et al26 Battal et al27 Yuhua et al29

Author

Table 2. Studies targeting anticoagulation

↑ and ↓ indicate significant changes (P < .05); ≈ indicates no effect. ↑↑ and ↓↓ indicate significant changes compared to ↑ and ↓ within the same study. bw, bodyweight; DWP, deep wound progression; i.v., intravenous; i.p., intraperitoneal; SWP, superficial wound progression.

Rat Rat

Animal

Battal et al15 Tobalem et al19

Author

Table 1. Studies targeting perfusion

n.a. ↑ ↓ ↓

DWP

↓ Delayed Delayed ↓↓ ↓ ↓ ≈

DWP

Journal of Burn Care & Research Volume 36, Number 3 Schmauss et al   e179

Pig

Rat

Rabbit

Rat Rabbit

Rat Rat Pig

Singer et al34

Sun et al35

Bucky et al36

Choi et al37 Mileski et al38

Eski et al40 Uygur et al41 Singer et al42

Anti-TNF-α-HA-conjugates Antibodies to IL-6 MAb to CD18 (5 sec-burn) MAb to CD18 (10 sec-burn) MAb to CD11/CD18 MAb to CD18 MAb to ICAM-1 Cerium nitrate Simvastatin Clobetason propionate

Semapimod

Agent

Topical i.p. Topical

i.v. i.v.

i.v.

Topical

i.v.

Mode

After (immediately) After (30 min) After (immediately)

After (immediately) After (30 min)

After (30 min)

After (24 hr)

After (1 hr)

Time

Regimen

Single Repetitive Continuous (14 days)

Single Single

Single

Single Repetitive Repetitive

Application

50, 100 and 150 μl 1 mg/kg bw 2 mg/kg bw 0.04 M for 30 min 5 mg/kg bw 0.05%

2 mg/kg bw

200 μl

1 mg/kg bw

Dosage

21 days 7 days 14 days

24 hr 72 hr

8 days

7 days

7 days

Follow-Up ≈ ≈ ↓ ≈ ↓ ≈ ↓ n.a. n.a. ↓ ↓ n.a.

Inflammation ↓ ↓ ↓ ≈ ↓ ≈ ↓ ↓ ↓ ↓ ↓ ≈

SWP ↓ ↓ n.a. n.a. ↓ ≈ ↓ n.a. n.a. ↓ ↓ ≈

DWP

44

Deferoxamine Rosiglitazone U75412E (lazaroid) Rapamycin N-acetylcystein Human copper-zinc superoxide dismutase

Rat Rat Rat Rat Rat Rat p.o. i.m. i.p. i.p. or p.o. i.v.

i.v.

Mode

After (30 min) After (immediately or 1 hr) After (immediately) After (1 hr) After (20 min)

After (1 hr)

Time

Repetitive Single Single Repetitive Single

Repetitive

Regimen

1–100 μg/kg bw purified or 4–40 mg/kg bw crude 10, 20, and 100 mg/kg bw 4 mg/kg bw 2 mg/kg bw 1 mg/kg bw 100 (i.p.)/490 mg/kg bw (p.o.) 20 mg/kg bw

Dosage

↑ and ↓ indicate significant changes (P < .05); ≈ indicates no effect. bw, bodyweight; DWP, deep wound progression; i.m., intramuscular; i.p., intraperitoneal; i.v., intravenous; n.a., not available; p.o., per os; SWP, superficial wound progression.

Curcumin purified or crude

Agent

Rat

Animal

Application

7 days 5 days 3 days 10 days 7 days

7 days

Follow-Up

≈ ↓ ↓ n.a. ↓ ≈

↓

SWP

≈ ↓ ↓ ↓ n.a. n.a.

↓

DWP

e180   Schmauss et al

Taira et al48 Choi et al49 Xiao et al50 Deniz et al51 Shalom et al53

Singer et al

Author

Table 4. Studies targeting antiapoptosis

↑ and ↓ indicate significant changes (P < .05); ≈ indicates no effect. bw, bodyweight; DWP, deep wound progression; HA, hyaluronic acid; ICAM, intercellular adhesion molecule; IL, interleukin; i.p., intraperitoneal; i.v., intravenous; MAb, monoclonal antibody; n.a., not available; SWP, superficial wound progression; TNF, tumour necrosis factor.

Animal

Author

Table 3. Studies targeting anti-inflammation



Journal of Burn Care & Research May/June 2015

Rat

Rat Pig Pig Rat

Türkaslan et al57

Rizzo et al58 Macri et al59 Singer et al60 Singer et al61

↑ and ↓ indicate significant changes (P < .05); ≈ indicates no effect. ATA, atmosphere absolute; bw, body weight; DWP, deep wound progression; i.m., intramuscular; i.v., intravenous; MSC, mesenchymal stem cells; n.a., not available; SWP, superficial wound progression.

↓ ≈ ↓ ↓ n.a. ≈ n.a. ↓ Single Single Single Single

Rat Germonpré et al56

Hypothermia Burn wound excision Debrase® MSC

Pig

Negative pressure (−125 mm Hg) Hyperbaric oxygen Piracetam Hyperbaric oxygen

i.m.

Topical Topical Topical i.v.

After (immediately or 2 hr) After (immediately) After (immediately) After (1 hr)

Repetitive After (30 min)

4 hr 1 ml (106 cells/ml)

5 days

24 hr 7 days 48 hr 7 days

↓ ↓ ↓ n.a. n.a. ↓ 3 days

100% O2 at 203 kPa 200 mg/kg bw 2.5 ATA two times/day for 1 or 5 days 31–33°C for 4 hr Repetitive After (4 hr)

↓ n.a. 12 days 125 mm Hg for 6 hr Single Topical

After (immediately or 12 hr)

Schmauss et al   e181

Morykwas et al55

Time Agent Animal Author

Table 5. Studies targeting other mechanisms

Mode

Application

Regimen

Dosage

Follow-Up

SWP

DWP

Journal of Burn Care & Research Volume 36, Number 3

in tissue death.9 If kept untreated, persisting low levels of perfusion have shown to harm tissue integrity in the zone of stasis due to local hypoxia, lack of nutrients, and accumulation of toxic metabolites.14 Burn injuries increase plasma levels of endothelin, an endogenous vasoconstrictor.15 Battal et al15 therefore investigated the effect of TAK-044, a non-selective endothelin-A and endothelin-B receptor-antagonist on burn wound progression in rats. TAK-044 was administered intravenously (i.v.) immediately after burn injury and induced a significant dose-dependent increase of skin perfusion, resulting in less edema-formation (controls: 74.3 ± 3.1% vs TAK-044: 44.6 ± 1.0% at day 7; P < .05), decreased inflammation, and significantly better tissue survival, both in surface (controls: 99.1 ± 1.1 vs TAK-044: 13.1 ± 1.1% necrosis at day 7; P < .05) and depth (full thickness vs partial thickness burns with viable hair follicles in control and treatment group, respectively). The most significant results were achieved with 1 mg/kg body weight (bw) TAK-044. Lower doses were not effective, higher doses decreased systemic blood pressure, eventually aggravating critical perfusion in the zone of stasis. Currently, local cold water treatment for approximately 20 minutes is still recognized as the accepted standard for first-aid treatment in burns because of heat dissipation as well as anti-inflammatory, analgetic, and anti-edematous effects.16–18 The treatment’s major drawback, however, is hypothermia-induced vasoconstriction eventually aggravating critical perfusion conditions. Tobalem et al19 therefore evaluated the effect of burn treatment using lukewarm water in order to reduce hypothermia-induced perfusion breakdown and to delay secondary burn wound progression. The authors investigated cold water (17°C) application and warm water (37°C) application for 20 minutes in rats and compared it to untreated animals. Both the approaches were able to significantly delay burn depth progression; however, at day 7, full thickness burn depth was comparable in all the three groups. Interestingly, only warm water application significantly reduced surface extension of the burn (controls: 94 ± 2% vs cold water: 81 ± 4% and warm water: 65 ± 4% at day 7; P < .05). This was attributed to a lesser degree of perfusion failure immediately after burn induction, respectively, to a restoration of baseline perfusion conditions within the first 4 days after burn (controls: 80 ± 2% vs cold water: 91 ± 3% and warm water: 103 ± 4% at day 4; P < .05). Thereafter, Tobalem et al20 investigated dosedependent effects of erythropoietin (EPO) administration on burn wound progression in rats. Beside



e182   Schmauss et al

its hematopoietic effects, EPO has shown to induce vasodilation, reduce inflammation, and induce angiogenesis.21,22 Following the immediate first-aid treatment using local cold water for 20 minutes, EPO was administered intraperitoneally (i.p.) daily at 500 (EPO500) and 2.500 IU/kg bw (EPO2.500) for 5 days and compared to local cooling only. Only the EPO500 group showed decreased surface extension (EPO500: 38 ± 7% vs controls: 81 ± 4% [P = .002] and vs EPO2.500: 68 ± 4% [P = .029] at day 7) and reduced depth progression of the burn to the intermediate dermis, eventually enabling spontaneous healing due to the maintained skin-appendages.6 Better skin survival correlated with increased skin-perfusion that was mediated by increased nitric oxide-expression (control: 23 ± 8% vs EPO500: 73 ± 14% [P = .006] and EPO2500: 66 ± 8% [P = .066] at day 1). The worse outcome of EPO2.500 was partly associated with the rapid and significant hematocrit increase compared to EPO500, potentially impairing blood rheology within the zone of stasis. Inflammation and angiogenesis were significantly reduced and increased in a dose-dependent manner. Signs of neoangiogenesis were observed from day 4 on, a time point at which necrosis is already demarcated. The authors therefore concluded that EPO-induced neoangiogenesis does not seem to contribute to the prevention of secondary burn progression, indicating that immediately after thermal injury, mechanisms that maintain perfusion within the critically perfused zone of stasis are necessary to prevent tissue from breakdown. Then, Tobalem et al23 investigated the timedependent effects of EPO-administration on secondary burn wound progression in rats. After local cold water application for 20 minutes, EPO500 was either administrated i.p. 45 minutes (EPO45m) or 6 hours post-burn (EPO6hrs) and daily for 5 days. After 7 days, the burn wound progression was significantly decreased to the intermediate dermis only in the EPO45m group, whereas full-thickness burn wound progression was observed in the EPO6hrs and control group. Administration of EPO resulted in a time-dependent, significant reduction of surface necrosis on day 7 (control: 78 ± 4% vs EPO45m: 45 ± 8% and EPO6hrs: 65 ± 4%; P = .017). Baseline perfusion was re-established at day 4 in the EPO45m group, whereas EPO6hrs restored baseline perfusion conditions by day 7. In analogy to the first study,20 the authors observed a nitric oxide-mediated vasodilation and a decreased leukocyte response that was independent of the administration time-point of EPO. According to the authors, these two effects might have contributed to the positive effects of EPO on burn wound progression.

Journal of Burn Care & Research May/June 2015

Anti-Coagulatory Agents Local burns cause acute thrombosis and occlusion of microvessels mainly in the dermis and, if the burn reaches a certain depth below the dermis, also in the subcutaneous tissue (Table 2).24,25 Currently, many substances with anti-coagulatory properties are effectively used in medicine and could therefore prevent hyperthermia-induced hypercoagulation. However, in a clinical setting, the risk of bleeding complications, eg, after burn excision, is always to be kept in mind. Işik et al11 evaluated recombinant tissue–type plasminogen activator (r-tPA), the synthesized form of a second-generation thrombolytic agent, on burn wound progression in rats. r-tPA was administered i.v. at a dosage of 1 mg/kg bw 2 hours after burn induction and compared to a control group receiving the same volume of saline. After 7 days, the perfusion in the zone of stasis was significantly higher in the treatment group with significantly more vital interspaces (control: 31.8% vs r-tPA: 87.8%; P < .05). Meyerholz et al26 administered activated protein C (APC) (Drotrecogin alfa), an anticoagulatory and anti-inflammatory agent. Rats received lactatedRinger’s solution (LRS) plus 24 μg APC/kg/h i.v. immediately after burn injury for 5 hours and were compared to LRS-treated animals. Evaluation 5 hours after burn injury revealed significantly decreased perfusion, deeper burns, and increased inflammation in animals treated with APC compared to LRS-treated animals. In our opinion, this short observationperiod of 5 hours after burn injury might however not be enough to evaluate burn wound progression that usually takes 48 to 72 hours. Battal et al27 analyzed hypercoagulability using beraprost-sodium, a prostaglandin I2-analogue that has anti-platelet aggregation and vasodilatory effects, eventually resulting in reduced blood viscosity. Intraperitoneal administration of 0.015 mg beraprost-sodium in rats immediately after burn was compared to untreated controls. At 24 hours, the treatment showed significantly better perfusion conditions and reduced edema-formation in the zone of stasis, resulting in a significant reduction of surface (control: 99.1 ± 1.1% vs beraprostsodium: 13.1 ± 1.1%; P < .05) and depth progression (control: full thickness vs beraprost-sodium: partial thickness burn with viable hair follicles) of the burn wound at day 7. Application of 0.02 mg resulted in symptomatic tachycardia and was therefore not further investigated. Poloxamer-188 (P-188) is a surfactant that has an anticoagulatory effect due to the prevention of endothelial cell injury and reduction of leukocyte

Journal of Burn Care & Research Volume 36, Number 3

adherence.28 Yuhua et al29 showed that i.v. administration of P-188 at a dosage of 200 mg/kg bw every 24 hours, first administered immediately after burn injury, was able to significantly reduce burndepth progression at 72 hours in rats compared to untreated animals. Improved tissue survival was associated with higher cellular metabolism (Na-KATPase in control: 4.38 ± 0.58 U/mgprot vs P-188: 6.1 ± 0.75 U/mgprot; P < .01), decreased oxidative damage (malonaldehyde in control: 76.7 ± 9.5 nmol/ mgprot vs P-188: 0.92 ± 0.12 nmol/mgprot; P < .01), and reduced inflammation in the zone of stasis.

Anti-Inflammatory Agents Inflammation may induce both local and systemic complications after burns, eventually endangering tissue survival within the zone of stasis (Table 3).30 Amongst other things, plasma levels of histamine, complement and xanthine oxidase rise and contribute to the secondary burn wound progression.31 In severe cases, burns can be accompanied by a systemic inflammatory response syndrome, often due to a systemic increase of tumor necrosis factor-α (TNF-α).32 Also, enhanced aggregation of activated neutrophils aggravates the inflammatory response, particularly in the zone of stasis.33 Singer et al34 aimed at reducing TNF-α levels through the application of Semapimod, a selective inhibitor of macrophage-derived TNF-α and interleukin (IL)-1 production, in pigs. The authors compared i.v. administration of 1 mg/kg bw Semapimod 1 hour post-burn to a repeated administration of Semapimod at 1 hour and 24 hours post-burn and untreated controls. Additionally, all groups received daily dressings with silver-sulfadiazine crème (Flammazine®), commonly used in the acute care of burn wounds. Semapimod significantly reduced the number of thrombosed microvessels resulting in a decreased burn depth progression and faster reepithelialization. Semapimod did not decrease local cytokine-levels, indicating that other mechanisms might play a role for tissue protection. Sun et al35 topically applied antibodies (Ab) targeting TNF-α or interleukin-6 (IL-6) conjugated to hyaluronic acid (HA) onto partial-thickness burn wounds of rats at day 1, 3, and 5 after eschar removal and compared wound healing to untreated controls. Anti-TNF-α-HA conjugated Abs were able to significantly reduce burn depth progression (P < .001) on day 7 that correlated with a decreased macrophage infiltration (P < .05) and IL-1b levels in the tissues (P = .005). Administration of Ab to IL-6, a mediator

Schmauss et al   e183

of the inflammatory cascade, did not prevent burn wound progression. Bucky et al36 investigated the inflammatory response after local burns on a cellular level in rabbits and therefore administered the monoclonal antibody (MAb) 60.3 i.v. to block the leukocyte adherence glycoprotein cluster of differentiation (CD)18. Local burns of 5 and 10 seconds were induced and treatment with 2 mg/kg bw MAb 60.3 was initiated 30 minutes later. The controls received saline only. Following a 5-second burn, the wound contraction (control: 75.0 ± 2.2% vs MAb 60.3: 64.0 ± 10.2% contraction at 18 days; P < .05), thickness of the eschar and edema-formation were significantly reduced in the treatment group compared to controls after 8 days. Histology revealed a significant increase of live hair follicles (control: 1.5 ± 0.9 vs MAb 60.3: 11.8 ± 8.9 per high power field at day 8; P < .05) and a significant reduction in burn surface progression (control: 4.3 ± 0.3 cm2 vs MAb 60.3: 3.6 ± 0.3 cm2 mean surface area/burn site at 24 hours; P < .0001) in treated animals. In the 10-second groups, there were no significant differences between the treated animals and the controls. Tissue protection was associated with an inhibition of leukocyte aggregation and eventually improved perfusion in the zone of stasis. Choi et al investigated the effect of impaired leukocyte adherence on burn wound progression in rats.37 Immediately after burn induction M2, a MAb blocking leukocyte-leukocyte adherence through the adhesion sites CD11b/CD18, was administered i.v. at doses between 25 μl and 150 μl/kg bw. At 24 hours, a dose-dependent significant increase in local perfusion conditions was observed in the groups receiving 50 μl, 100 μl, or 150 μl M2 compared to the control animals, resulting in a significant reduction of burn wound progression in surface (controls: 89 and 92% vs M2: 0–28% necrotic interspaces at 24 hours; P < .05) and depth. However, the follow-up of 24 hours for planimetry and 2 hours for histology seem to be very short for evaluation of burn wound progression, since this phenomenon usually takes 48 to 72 hours. Mileski et al38 knocked out the complex responsible for endothelial-leukocyte adherence in order to prevent burn wound progression in rabbits. MAb directed to the leukocyte-CD18-adhesioncomplex (1 mg/kg bw) or its endothelial ligand, intercellular-adhesion-molecule-1 (ICAM-1, CD54: 2 mg/kg bw) were administered i.v. 30 minutes after burn. At 72 hours, perfusion in the zone of stasis was equal or above baseline in all the antibody-treated groups, while perfusion in the control animals was



e184   Schmauss et al

34.7 ± 12% of baseline in the control animals (P < .05). This resulted in less burn wound progression at the surface in treated animals compared to controls (5% vs 41% necrosis of unburned interspaces; P < .05). Cerium nitrate (CN) is a topical antiseptic agent that has been reported to decrease burn-related mortality through its anti-inflammatory effects.39 Eski et al40 demonstrated in a rat model that topical application of 0.04  M CN for 30 minutes immediately after burn injury was associated with significantly improved local perfusion and significantly reduced inflammatory response and decreased burn wound progression in surface (control: 10% vs CN: 90% viable tissue in the zone of stasis; P < .01) and depth at day 21 after burn. Uygur et al41 analyzed the effect of Simvastatin, a commonly used statin-analogue with non-lipidrelated pleiotropic effects on the vascular wall and the progression of burn wounds, in rats. Simvastatin was first administered i.p. at a dosage of 5 mg/kg bw 30 minutes after burn and continued on a daily base for 7 days. A significant decrease of inflammation, coagulation, and intravascular fibrin-collection was observed at day 7 within the zone of stasis, resulting in significantly improved tissue survival at the surface and in the depth. Corticosteroids have distinct anti-inflammatory properties, yet their use is controversially discussed in burn wound healing. Singer et al42 showed that the topical co-application of steroids and antimicrobial agents in pigs was not able to prevent secondary burn wound progression.

Reactive Oxygen Species and Anti-Apoptotic Agents Another way of interacting with progressive tissue damage in local burns is to decrease the levels of reactive-oxygen-species (ROS) (Table 4). Antioxidants (ie, superoxide-dismutase, deferoxamine) may neutralize small concentrations of ROS. If tissue concentration exceeds a certain threshold, ROS can also induce cellular apoptosis and tissue damage. Decreasing levels of ROS and enhancing cellular tolerance to apoptotic cell death is therefore a therapeutical option in preventing burn wound progression.43 Singer et al44 investigated the effect of curcumin, a constituent of the oriental spice turmeric with antioxidative, anti-inflammatory, and anti-apoptotic effects,45–47 on burn wound progression in rats. Crude or purified curcumin was administered i.v. at different dosages (1–100 μg/kg bw purified or

Journal of Burn Care & Research May/June 2015

4–40 mg/kg bw crude) 1 and 24 hours after burn induction. Another group received only deferoxamine, which acts as an iron chelating agent. The authors demonstrated that both, crude and purified curcumin, significantly reduced burn wound progression on the surface (control: 74% vs curcumin: 26–53% necrosis of unburned interspaces; P < .05) and in depth in a dose-dependent manner. Deferoxamine alone was not able to reduce burn wound progression. The authors did not observe any toxic effects at higher doses or purity of curcumin. Taira et al48 investigated the effect of rosiglitazone, a PPAR-γ-ligand (nuclear-hormone-receptor), which plays an important role in cellular proliferation and inflammation, in a rat model. The authors administered 4 mg/kg bw rosiglitazone orally 30 minutes, as well as 24 and 48 hours after burn. Seven days later, the extension of local burns that progressed in surface and depth to full-thickness lesions in untreated animals could be significantly reduced with rosiglitazone (control: 90% vs rosiglitazone: 72% necrosis of unburned interspaces; P = .02). Decreased burn progression was associated with improved perfusion conditions and anti-inflammatory effects that did not reach statistical significance compared to the controls. Choi et al49 hypothesized, that oxygen radicals present in the zone of stasis impair endothelial integrity as a consequence of peroxidation of fatty acids. U75412E, a lazaroid that blocks lipid peroxidation, was administered intramuscularly (i.m.) in rats at a dosage of 2 mg/kg bw either immediately after or at 1 hour , respectively 2 hours after burn. At 24 hours, microvascular patency and so tissue perfusion were significantly increased with lazaroid-administration immediately and 1 hour (152 ± 27% and 123 ± 21% of baseline perfusion, respectively) after burn induction compared to controls (P < .001). At day 5, administration of lazaroid significantly reduced burn wound progression in surface (control: 100% vs U75412E: 13% necrosis of unburned interspaces; P < .05) and depth. The authors speculated that the inhibition of lipid-peroxidation by U75412E would protect endothelial cells, thereby preserving endovascular integrity and eventually vascular patency. Autophagy has been reported to be protective against apoptosis, ischemic injury and inflammatory diseases. Xiao et al50 investigated the effect of rapamycin, an autophagy-inducer, on burn wound progression in rats and administered 1 mg/kg bw rapamycin i.p. immediately after burn. Rapamycininduced perfusion, as well as decreased inflammation and apoptotic cell death resulted in a decreased burn depth (more residual hair follicles and less

Journal of Burn Care & Research Volume 36, Number 3

collagen denaturation) and shorter time until complete re-epithelialization (control: 24.8 ± 1.3 days vs rapamycin: 22.5 ± 1.4 days; P < .01) compared to vehicle-treated animals. Deniz et al51 administered systemically N-acetylcysteine (NAC), a widely used antioxidative drug, 1 hour after burn induction for 10 days. The drug was administered to rats via oral (490 mg/kg bw) or i.p. route (100 mg/kg bw). The authors found significantly less surface progression of the burn wound compared to the control animals in both the treatment groups (control: 4% vs i.p. NAC: 27% and p.o. NAC: 20% vital unburned interspaces; P < .001). No differences between the treatment groups were noted. Interestingly, the levels of malondialdehyde, a marker for oxidative stress, did not differ between the groups. Human-recombinant copper-zinc-superoxidedismutase (Hr-CuZnSOD) is an enzyme that neutralizes superoxide radicals and has proven to be effective in increasing the survival of critically perfused flaps.52 Accordingly, Shalom et al53 evaluated the i.v. administration of Hr-CuZnSOD at a dosage of 20 mg/kg bw 20 minutes after burn injury in rats. This agent did not show any effect in preventing local burn injury from wound progression.

Various Other Agents and Devices Most of the therapeutical approaches are focused on maintaining perfusion above the threshold to tissue death, hindering intravascular coagulation, inducing anti-inflammatory processes and preventing apoptosis. Nevertheless, other tissue protective settings have been studied to limit burn wound progression (Table 5). The application of sub-atmospheric pressure is widely used in the therapy of chronic wounds. In most centers, the continuous application of 125 mm Hg vacuum is considered to be the standard, since the formation of granulation tissue showed to be significantly quicker with 125 mm Hg compared to 25 mm Hg and 500 mm Hg.54 Morykwas et al55 applied negative pressure (NP) of 125 mm Hg to burn wounds in pigs and compared those to burn wounds without NP-treatment within the same animal. Application of NP within 12 hours after burn induction for 6 hours was associated with significantly decreased burn depth progression (controls: 0.885 ± 0.115 mm vs NP immediately after burn: 0.095 ± 0.025 mm and NP after 12 hours: 0.275 ± 0.025 mm burn depth; P < .001) and inflammatory response compared to the controls. Increasing the time of NP-application to 5 days did not show any benefit compared to NPapplication for 6 hours. Hyperbaric oxygen therapy (HBOT) has also shown to decrease burn wound progression.

Schmauss et al   e185

Germonpré et al56 demonstrated in a rat model that the use of 100% oxygen pressurized at 203 kPa for 60 minutes resulted in a significant reduction of dermal leukocyte infiltration as well as a destruction of the basal membrane and the skin appendages (control: 73 ± 17% vs HBOT: 61 ± 7% destroyed skin appendages/microscopic field; P < .05), resulting in a significantly decreased depth of progression of the burn. Treatment was initiated 4 hours after burn injury and continued every 8 hours for the first day respectively then every 12 hours for the second and third day. Türkaslan et al57 confirmed the protective effects of HBOT on burn wound progression by applying oxygen at 2.5 atmosphere absolute 30 minutes after burn injury for 90 minutes twice daily. One group of rats was treated for 24 hours, the other group for 5 days and compared to the untreated controls. At 24 hours, surface necrosis did not differ significantly between the groups. Though, significantly reduced progression of surface necrosis was reached after 5 days in treated animals (P < .05). Decreased burn wound progression in depth and surface correlated with an increased vessel count (P < .001), indicating neovascularization in animals receiving treatment over 5 days. Germonpré et al56 administered Piracetam i.m. to rats twice daily for 3 days, starting 4 hours after the burn injury. The pro-rheological properties of Piracetam allow its use for cerebral vascular insufficiency and frostbite. Piracetam was able to prevent destruction of the basal membrane, though, subepidermal leukocyte-infiltration and destruction of the skin appendages were not significantly decreased compared to the controls. Rizzo et al58 applied systemic hypothermia of 31 to 33°C for 4 hours immediately or 2 hours after burn injury in rats. The authors used cold water circulating blankets to induce hypothermia. Burn depth was significantly lower already at 6 hours in the group undergoing immediate hypothermia (P = .017), but only at 24 hours for the group undergoing hypothermia 2 hours post-burn (P < .001), when compared to the controls. The histological results correlated with an over-expression of skin protective genes, including chemokine (C-C motif) ligand (CCL)4, CCL6, and C-X-C motif chemokine (CXCL)13 respectively; a decreased expression of the tissue remodelling gene matrix metalloprotease-9. In our opinion, the follow-up of 24 hours might be too short to evaluate burn wound progression. Furthermore, the authors did not discuss the potentially detrimental effects of hypothermia-induced vasoconstriction on the perfusion in the zone of stasis.



e186   Schmauss et al

Macri et al59 postulated that burn wound progression would develop independently of the core zone. The authors therefore excised all burned areas immediately after local burn injury in pigs. The intercalated interspaces of unburned skin were left in place and kept untreated. Two full-thickness excisional wounds of the size of the brass-comb were additionally created on the back of each animal and served as controls. Histological analysis showed that immediate excision of the burn wounds could neither prevent nor limit burn wound progression of the interspaces after 7 days. Singer et al60 studied the effect of topical bromelain-based enzymatic debridement (Debrase®) in pigs. The injured keratin layer was removed immediately after burn and Debrase® was applied to the wound and compared to a vehicle-only containing gel. The gels were wiped off after 4 hours and a thin layer of silver-sulfadiazine (Flammazine®) was applied. At 4 hours, improved dermal collagen structure, as well as decreased microvascular thrombosis and follicular necrosis were observed in Debrase®-treated wounds compared to the controls. After 48 hours and despite wound desiccation, only one third of the unburned interspaces showed full-thickness burns in Debrase®treated wounds compared to full-thickness burns of all interspaces in the control wounds (P < .05). However, a follow-up of 48 hours might be too short to finally evaluate burn depth, since burn depth progression might simply be delayed under treatment with Debrase®, as seen with warm water application.19 Mesenchymal stem cells (MSC) are known to differentiate into definite cell populations of conjunctive tissue and dermis. Burns may destroy the local pool of MSCs. Singer et al61 therefore administered MSCs i.v. in rats to replace necrotic and apoptotic cells after burn injury. MSCs were cultured in a rat marrow stromal cell growth medium kit and administered i.v. in the tail vein. The treatment group received 106 ratspecific MSCs 1 hour after burn. At day 7, a significant reduction of burn wound progression was observed in the treated animals (control: 100% vs MSC: 80% necrosis of unburned interspaces; P < .0001). MSCs have also shown to significantly reduce apoptosis in local burns and may therefore be one of the therapeutical approaches to be targeted at.62

DISCUSSION Transfer into Clinical Practice This systematic review highlights several promising experimental approaches to treat secondary burn wound progression. Some of the presented substances and devices have already proven to be of value in

Journal of Burn Care & Research May/June 2015

many clinical settings. For example, EPO is used to increase hematocrit in patients suffering from chronic renal failure or massive blood loss after surgery and trauma.63 Likewise, simvastatin is used to lower cholesterol,64 and application of sub-atmospheric pressure is an effective treatment of chronic wounds.54 The question therefore arises why none of these approaches has found its way into daily clinical use in the local burn care. One reason might be that the substances we refer to — particularly if administered systemically — have side effects that are not outweighed by the preventive effect on secondary burn wound progression. It is worth mentioning that endothelin receptor antagonists may cause severe hypotension, anti-coagulatory agents may provoke bleeding and EPO may increase the hematocrit and thereby deteriorate blood rheology. Another reason might be the fact that the pathophysiology of burn wound progression seems to be different in humans compared to animals and even may differ among animal species. Especially burn-induced microvascular thrombosis may play a different role in the pathophysiology of burn wound progression, which finally limits the transferability of anticoagulatory agents from animal experimentation into clinical studies. A third reason for lacking clinical translation is the fact that some agents such as MSC, Hr-CuZnSOD or mAB M2 do not have approval by the Food and Drug Administration (FDA). All studies had a high level of quality due to their prospective design, the inclusion of at least one control group and one treatment group and the random assignment of the animals to the groups. However, the short follow-up of less than 4 days in some studies seems to be a bias to us, because we are evaluating the effectiveness of a treatment on the progression of skin necrosis after local burn. As other authors did, we have been able to show that progression of necrosis in surface and depth occurs over 4 to 5 days to reach a plateau if kept untreated. Finally, we believe that the ideal approach to treat secondary burn wound progression should occur with substances or devices that are inexpensive, easily applicable, and widely available. Only some experimental approaches meet these criteria for a quick translation into clinical practice. The application of warm water as first aid treatment indeed seems to be counterintuitive and it does not fulfill the current guidelines recommending the use of cold water. Yet, warm water at 37°C has proven — in contrast to cold water — to reduce burn surface progression and delay burn depth progression, finally opening a therapeutic window for further treatment. This may outweigh the missing analgesic effect of cold water. Its costs, applicability, and availability are comparable to cold water. The

Journal of Burn Care & Research Volume 36, Number 3

combination of cold water and warm water treatment as first-aid therapy after local burn injury may therefore be of high interest. The systemic application of Simvastatin has also proven to be effective in treating burn wound progression in a rat model. This well-known agent is FDA-approved for the treatment of hypercholesterolemia. However, it may cause muscular pain and injury in some patients, particularly if used at a higher dose. These potential side-effects might be balanced by its preventive effects on burn wound progression. EPO might be another promising agent to treat progression of local burn wounds. EPO is FDAapproved and has proven beneficial for the treatment of anemia in chronic renal failure and cancer patients and for decreasing blood transfusion requirements after major surgery. Systemic EPO administration has shown to reduce both, surface progression and burn depth progression, if the first dose of 500 IU/kg bw is administered 45 minutes after the injury. Higher doses of EPO resulted in a hematocrit-increase and thereby impaired rheology. In our opinion, non-erythropoietic EPO that exhibits the same tissue protective effects like EPO (eg, carbamylated EPO (CEPO) or, ARA 290) may be a promising approach for the future. The topical application of EPO directly onto the burn wound might also be a way to circumvent side-effects of systemic EPO-administration that are detrimental for the microcirculation. Of note, Machens and colleagues are conducting a clinical study on the regenerative effects of EPO after burn injuries.65 Cerium nitrate is an antiseptic agent widely used in topical burn wound care. Therefore, its ability to reduce burn surface and depth progression in an experimental approach is particularly interesting and should be evaluated in a clinical study. Agents such as rosiglitazone, rapamycin, MSCs, or antibodies to IL-6, CD11, CD18, or ICAM-1 have been demonstrated to reduce burn wound progression but may not find their way into clinical practice in the near future, since they are expensive, exhibit major side-effects and/or have not yet been FDA-approved. Other than in clinical studies, the declaration of the level of evidence is not established in experimental studies in animals. All studies included in this systematic review article are of high quality with approaches that seem to be appealing. Nevertheless, the transferability into a clinical situation and the applicability on humans has not yet been determined.

CONCLUSION Millions of burn injuries occur every year, being a medical and eventually an economical challenge

Schmauss et al   e187

worldwide. The consequences of burns can be devastating for the patients and their environment. Secondary burn wound progression results from a complex interplay of many processes that depend amongst other things upon perfusion, coagulation, inflammation, and cell death. In local burns, morbidity, hospital stay, and eventually the nonproductive time primarily correlate with burn depth. The treatment of secondary burn wound progression is therefore of high interest. Warm water, simvastatin, EPO, or cerium nitrate may represent particularly promising approaches for translation into clinical use in the near future. References 1. Bessey PQ, Phillips BD, Lentz CW, et al. Synopsis of the 2013 annual report of the national burn repository. J Burn Care Res. 2014 May-Jun;35 Suppl 2:S218–34. 2. Singh V, Devgan L, Bhat S, Milner SM. The pathogenesis of burn wound conversion. Ann Plast Surg 2007;59:109–15. 3. Kao CC, Garner WL. Acute burns. Plast Reconstr Surg 2000;105:2482–92; quiz 2493; discussion 2494. 4. Atiyeh BS, Gunn SW, Hayek SN. State of the art in burn treatment. World J Surg 2005;29:131–48. 5. Feck GA, Baptiste MS. Burn injuries: epidemiology and prevention. Accid Anal 1979;11:129–36. 6. Jackson DM. The diagnosis of the depth of burning. Br J Surg 1953;40:588–96. 7. Astrup J, Siesjö BK, Symon L. Thresholds in cerebral ischemia—the ischemic penumbra. Stroke 1981;12:723–5. 8. Harder Y, Amon M, Georgi M, Banic A, Erni D, Menger MD. Evolution of a “falx lunatica” in demarcation of critically ischemic myocutaneous tissue. Am J Physiol Heart Circ Physiol 2005;288:H1224–32. 9. Regas FC, Ehrlich HP. Elucidating the vascular response to burns with a new rat model. J Trauma 1992;32:557–63. 10. Arturson G. Pathophysiology of the burn wound and pharmacological treatment. The Rudi Hermans Lecture, 1995. Burns 1996;22:255–74. 11. Işik S, Sahin U, Ilgan S, Güler M, Günalp B, Selmanpakoğlu N. Saving the zone of stasis in burns with recombinant tissue-type plasminogen activator (r-tPA): an experimental study in rats. Burns 1998;24:217–23. 12. Moher D, Liberati A, Tetzlaff J, Altman DG. PRISMA Group. Preferred reporting items for systematic reviews and meta-analyses: the PRISMA Statement. Open Med 2009;3:e123–30. 13. Despa F, Orgill DP, Neuwalder J, Lee RC. The relative thermal stability of tissue macromolecules and cellular structure in burn injury. Burns 2005;31:568–77. 14. Knabl JS, Bauer W, Andel H, et al. Progression of burn wound depth by systemical application of a vasoconstrictor: an experimental study with a new rabbit model. Burns 1999;25:715–21. 15. Battal MN, Hata Y, Matsuka K, et al. Reduction of progressive burn injury by using a new nonselective endothelin-A and endothelin-B receptor antagonist, TAK-044: an experimental study in rats. Plast Reconstr Surg 1997;99:1610–9. 16. Blomgren I, Eriksson E, Bagge U. Effect of cold water immersion on oedema formation in the scalded mouse ear. Burns Incl Therm Inj 1982;9:17–20. 17. Bartlett N, Yuan J, Holland AJ, et al. Optimal duration of cooling for an acute scald contact burn injury in a porcine model. J Burn Care Res 2008;29:828–34. 18. Van de Velde S, Broos P, Van Bouwelen M et al. European first aid guidelines. Resuscitation 2007;72:240–51.



e188   Schmauss et al

19. Tobalem M, Harder Y, Tschanz E, Speidel V, Pittet-Cuénod B, Wettstein R. First-aid with warm water delays burn progression and increases skin survival. J Plast Reconstr Aesthet Surg 2013;66:260–6. 20. Tobalem M, Harder Y, Rezaeian F, Wettstein R. Secondary burn progression decreased by erythropoietin. Crit Care Med 2013;41:963–71. 21. Bader A, Lorenz K, Richter A, et al. Interactive role of trauma cytokines and erythropoietin and their therapeutic potential for acute and chronic wounds. Rejuvenation Res 2011;14:57–66. 22. Günter CI, Rezaeian F, Harder Y et al. Erythropoietin in plastic surgery. Handchir Mikrochir Plast Chir 2013;45:252. 23. Tobalem M, Harder Y, Schuster T, Rezaeian F, Wettstein R. Erythropoietin in the prevention of experimental burn progression. Br J Surg 2012;99:1295–303. 24. Arturson G, Rammer L. Endogenous inhibition of fi brinolysis in patients with severe burns. Acta Chir Scand 1974;140:181–4. 25. Jackson DM. Second thoughts on the burn wound. J Trauma 1969;9:839–62. 26. Meyerholz DK, Piester TL, McNamara AR, et al. Pharmacologic modification to resuscitation fluid after thermal injury—is drotrecogin alfa the answer to arrest burn depth progression? J Trauma 2009;67:996–1003. 27. Battal MN, Hata Y, Matsuka K, et al. Reduction of progressive burn injury by a stable prostaglandin I2 analogue, beraprost sodium (Procylin): an experimental study in rats. Burns 1996;22:531–8. 28. Baskaran H, Toner M, Yarmush ML, Berthiaume F. Poloxamer-188 improves capillary blood flow and tissue viability in a cutaneous burn wound. J Surg Res 2001;101:56–61. 29. Yuhua S, Ligen L, Jiake C, Tongzhu S. Effect of Poloxamer 188 on deepening of deep second-degree burn wounds in the early stage. Burns 2012;38:95–101. 30. Dahiya P. Burns as a model of SIRS. Front Biosci (Landmark Ed) 2009;14:4962–7. 31. Friedl HP, Till GO, Trentz O, Ward PA. Roles of histamine, complement and xanthine oxidase in thermal injury of skin. Am J Pathol 1989;135:203–17. 32. Endo S, Inada K, Yamada Y, et al. Plasma tumour necrosis factor-alpha (TNF-alpha) levels in patients with burns. Burns 1993;19:124–7. 33. Moore FC Jr, Davis C, Rodrick M, Mannick JA, Fearon DT. Neutrophil activation in thermal injury as assessed by increased expression of complement receptors. N Engl J Med. 1986;314:948–53. 34. Singer AJ, McClain SA, Hacht G, Batchkina G, Simon M. Semapimod reduces the depth of injury resulting in enhanced re-epithelialization of partial-thickness burns in swine. J Burn Care Res 2006;27:40–9. 35. Sun LT, Friedrich E, Heuslein JL, et al. Reduction of burn progression with topical delivery of (antitumor necrosis factor-α)-hyaluronic acid conjugates. Wound Repair Regen 2012;20:563–72. 36. Bucky LP, Vedder NB, Hong HZ, et al. Reduction of burn injury by inhibiting CD18-mediated leukocyte adherence in rabbits. Plast Reconstr Surg 1994;93:1473–80. 37. Choi M, Rabb H, Arnaout MA, Ehrlich HP. Preventing the infiltration of leukocytes by monoclonal antibody blocks the development of progressive ischemia in rat burns. Plast Reconstr Surg 1995;96:1177–85; discussion 1186–7. 38. Mileski W, Borgstrom D, Lightfoot E, et al. Inhibition of leukocyte-endothelial adherence following thermal injury. J Surg Res 1992;52:334–9. 39. Sheidegger D, Sparkes B, Lüscher N, Schonenberger GA, Allgower M. Survival in major burns treated by one bathing in cerium nitrate. Burns 1992;18:296–300.

Journal of Burn Care & Research May/June 2015

40. Eski M, Ozer F, Firat C, et al. Cerium nitrate treatment prevents progressive tissue necrosis in the zone of stasis following burn. Burns 2012;38:283–9. 41. Uygur F, Evinc R, Urhan M, Celikoz B, Haholu A. Salvaging the zone of stasis by simvastatin: an experimental study in rats. J Burn Care Res 2009;30:872–9. 42. Singer AJ, McClain SA. The effects of a high-potency topical steroid on cutaneous healing of burns in pigs. Acad Emerg Med 2002;9:977–82. 43. Shupp JW, Nasabzadeh TJ, Rosenthal DS, Jordan MH, Fidler P, Jeng JC. A review of the local pathophysiologic bases of burn wound progression. J Burn Care Res 2010;31:849–73. 44. Singer AJ, Taira BR, Lin F, et al. Curcumin reduces injury progression in a rat comb burn model. J Burn Care Res 2011;32:135–42. 45. Kuttan R, Bhanumathy P, Nirmala K, George MC. Potential anticancer activity of turmeric (Curcuma longa). Cancer Lett 1985;29:197–202. 46. Sharma OP. Antioxidant activity of curcumin and related compounds. Biochem Pharmacol 1976;25:1811–2. 47. Srimal RC, Dhawan BN. Pharmacology of diferuloyl methane (curcumin), a non-steroidal anti-inflammatory agent. J Pharm Pharmacol 1973;25:447–52. 48. Taira BR, Singer AJ, McClain SA, et al. Rosiglitazone, a PPAR-gamma ligand, reduces burn progression in rats. J Burn Care Res 2009;30:499–504. 49. Choi M, Ehrlich HP. U75412E, a lazaroid, prevents progressive burn ischemia in a rat burn model. Am J Pathol 1993;142:519–28. 50. Xiao M, Li L, Hu Q et al. Rapamycin reduces burn wound progression by enhancing autophagy in deep second-degree burns in rats. Wound Repair Regen 2013. 51. Deniz M, Borman H, Seyhan T, Haberal M. An effective antioxidant drug on prevention of the necrosis of zone of stasis: N-acetylcysteine. Burns 2013;39:320–5. 52. Schein O, Westreich M, Shalom A. Effect of intradermal human recombinant copper-zinc superoxide dismutase on random pattern flaps in rats. Head Neck 2013;35:1265–8. 53. Shalom A, Kramer E, Westreich M. Protective effect of human recombinant copper-zinc superoxide dismutase on zone of stasis survival in burns in rats. Ann Plast Surg 2011;66:607–9. 54. Morykwas MJ, Simpson J, Punger K et al. Vacuum-assisted closure: state of basic research and physiologic foundation. Plast Reconstr Surg 2006;117:121–6. 55. Morykwas MJ, David LR, Schneider AM, et al. Use of subatmospheric pressure to prevent progression of partial-thickness burns in a swine model. J Burn Care Rehabil 1999;20(1 Pt 1):15–21. 56. Germonpré P, Reper P, Vanderkelen A. Hyperbaric oxygen therapy and piracetam decrease the early extension of deep partial-thickness burns. Burns 1996;22:468–73. 57. Türkaslan T, Yogun N, Cimşit M et al. Is HBOT treatment effective in recovering zone of stasis? An experimental immuno-histochemical study. Burns 2010;36:539–44. 58. Rizzo JA, Burgess P, Cartie RJ, Prasad BM. Moderate systemic hypothermia decreases burn depth progression. Burns 2013;39:436–44. 59. Macri LK, Singer AJ, Taira BR, McClain SA, Rosenberg L, Clark RA. Immediate burn excision fails to reduce injury progression. J Burn Care Res 2013;34:e153–60. 60. Singer AJ, McClain SA, Taira BR, Rooney J, Steinhauff N, Rosenberg L. Rapid and selective enzymatic debridement of porcine comb burns with bromelain-derived debrase: acutephase preservation of noninjured tissue and zone of stasis. J Burn Care Res 2010;31:304–9. 61. Singer DD, Singer AJ, Gordon C, Brink P. The effects of rat mesenchymal stem cells on injury progression in a rat model. Acad Emerg Med 2013;20:398–402. 62. Öksüz S, Ülkür E, Öncül O, et al. The effect of subcutaneous mesenchymal stem cell injection on stasis zone and

Journal of Burn Care & Research Volume 36, Number 3

apoptosis in an experimental burn model. Plast Reconstr Surg 2013;131:463–71. 63. Kaufman JS, Reda DJ, Fye CL, et al. Subcutaneous compared with intravenous epoetin in patients receiving hemodialysis. Department of Veterans Affairs Cooperative Study Group on Erythropoietin in Hemodialysis Patients. N Engl J Med 1998;339:578–83.

Schmauss et al   e189

64. Mölgaard J, von Schenck H, Olsson AG. Effects of simvastatin on plasma lipid, lipoprotein and apolipoprotein concentrations in hypercholesterolaemia. Eur Heart J 1988;9:541–51. 65. Günter CI, Bader A, Dornseifer U, et al. A multi-center study on the regenerative effects of erythropoietin in burn and scalding injuries: study protocol for a randomized controlled trial. Trials 2013;14:124.