Jean Rooney

Rapid and selective enzymatic debridement of porcine comb burns with bromelain-derived Debrase: acute-phase preservation of noninjured tissue and zone of stasis.

Deep burns are associated with the formation of an eschar, which delays healing and increases the risk of infection. Surgical debridement of the eschar is, at present, the fastest means to achieve an eschar-free bed, but the process can not differentiate between the viable tissue and the eschar and follow the minute irregularities of the interface between the two. We evaluated the efficacy and selectivity of a novel enzymatic bromelain-based debriding agent, Debrase® Gel Dressing (Debrase®), in a porcine comb burn model. We hypothesized that Debrase® would result in rapid debridement of the eschar without adverse effects on the surrounding uninjured skin. This is a prospective, controlled, animal experiment. Five domestic pigs (20–25 kg) were used in this study. Sixteen burns were created on each animals dorsum using a brass comb with four rectangular prongs preheated in boiling water and applied for 30 seconds, resulting in four rectangular 10 × 20 mm full-thickness burns and separated by three 5 × 20 mm unburned interspaces representing the zone of stasis. The burned keratin layer (blisters) was removed, and the burns were treated with a single, topical, Debrase® or control vehicle application for 4 hours. The Debrase®/control was then wiped off using a metal forceps handle, and the burns were treated with a topical silver sulfadiazine (SSD). The wounds were observed, and full-thickness biopsies were obtained at 4 and 48 hours for evidence of dermal thickness, vascular thrombosis, and burn depth, both within the comb burns and the unburned interspaces in between them. Chi-square and t tests are used for data analysis. A single 4-hour topical application of Debrase® resulted in rapid and complete eschar dissolution of all the burns in which the keratin layer was removed. The remaining dermis was thinner (1.1 ± 0.7 mm) than in the control burns (2.1 ± 0.3 mm; difference 0.9 mm [95% confidence interval: 0.3–1.4]) and was viable with no injury to the normal surrounding skin or to the unburned interspaces between the burns, which represents the zone of stasis. In control burns, the entire thickness of the dermis was necrotic. At 48 hours, Debrase®-treated areas were found partially desiccated under SSD treatment. The unburned interspaces demonstrated partial-thickness necrosis in two third and full-thickness necrosis in one third of wounds. In contrast, full-thickness necrosis was noted in all control interspaces (P = .05). In a porcine comb burn model, a single, 4-hour topical application of Debrase® resulted in rapid removal of the necrotic layer of the dermis with preservation of unburned tissues. At 48 hours, SSD treatment resulted in superficial tissue damage and partial preservation of the unburned interspaces.

A novel TGF-beta antagonist speeds reepithelialization and reduces scarring of partial thickness porcine burns.

Scar formation after thermal injury is common and results in significant aesthetic and functional impairment. Transforming growth factor beta (TGF-β) plays a significant role in scar formation. We tested the hypothesis that a novel TGF-β peptantagonist would reduce scar formation and wound contraction in partial thickness burns by using a randomized controlled experiment. The subjects include two domestic pigs (20–25 kg). Forty burns were created on the animal’s dorsum using an aluminum bar preheated to 80°C and applied for 20 seconds resulting in a partial thickness thermal burn extending half way down the dermis. Burns were treated every other day for 1 week, then twice weekly for 3 weeks with a topical TGF-β antagonist or its vehicle. Full thickness biopsies were obtained from all burns at 7, 10, and 14 days after injury. The wounds were completely excised after 28 days for histological assessment. Wound sections were stained with H&&E and evaluated by a dermatopathologist masked to treatment assignment for reepithelialization and depth of scar formation. We also determined the number of wounds at 28 days that healed with contracted, hour-glass shaped scars. Data were compared with &khgr;2 and t-tests. Twenty burns were treated with TGF-β antagonist and 20 with control vehicle. TGF-β antagonist increased the percentage of completely reepithelialized wounds at 14 days (90 vs 45%, P = .002) and reduced the percentage of contracted wounds (35 vs 65%, P = .02) and full thickness scars (10 vs 60%, P = .002) at 28 days. Treatment of partial thickness porcine burns with the TGF-β antagonist speeds reepithelialization and reduces scar formation and wound contraction in partial thickness porcine burns.

Validation of a porcine comb burn model

OBJECTIVE A brass comb burn model that creates 3 full-thickness burns separated by 3 interspaces of unburned skin representing the zone of ischemia has been described in rats. We evaluated this model in pigs. METHODS Design--observational. Subjects--6 pigs (20-25 kg). Interventions--4 burns created on each animal on the dorsum using a brass comb with 4 rectangular prongs preheated in boiling water and applied for 30 seconds resulting in 4 rectangular 10 x 20-mm full-thickness burns separated by three 5 x 20-mm unburned interspaces. Outcomes--wounds observed at 1, 2, 3, and 7 days for evidence of necrosis in unburned interspaces. Full-thickness biopsies from interspaces were evaluated with hematoxylin-eosin staining 7 days after injury for evidence of necrosis. Data analysis--the percentages of interspaces progressing to necrosis were analyzed with descriptive statistics. RESULTS Twenty-four comb burns with 72 unburned interspaces were created evenly distributed between the animals. The percentages of interspaces that progressed to full-thickness necrosis at 1, 2, 3, and 7 days after injury were 88.9% (64/72; 95% confidence interval [CI], 79.6%-94.3%), 88.9% (64/72; 95% CI, 79.6%-94.3%), 88.9% (64/72; 95% CI, 79.6%-94.3%), and 97.7% (70/72; 95% CI, 90.4%-99.2%), respectively. There was perfect agreement between gross inspection and histomorphology. CONCLUSIONS The comb burn model in swine results in the progression of most unburned ischemic interspaces to full-thickness necrosis within 1 to 7 days.

An in-vivo study of the wound-bursting strengths of octyl-cyanoacrylate, butyl-cyanoacrylate, and surgical tape in rats.

BACKGROUND Several non-invasive wound-closure devices are available. Clinical studies of low-tension lacerations suggest similar clinical outcomes with these devices. OBJECTIVE We compared the wound-bursting strengths (WBS) of octyl-cyanoacrylate (Dermabond), butyl-cyanoacrylate (Histoacryl Blue), and adhesive tape (Steri-Strips). METHODS Design-randomized, controlled, blinded experiment. Setting-university-based division of laboratory animal research. Subjects-15 Sprague-Dawley rats weighing 250-350 g. Interventions-standardized 2-cm full-thickness incisions were made in duplicate on both sides of the rats dorsum with a #15 surgical blade and closed with one of the three study wound-closure devices following manufacturer instructions. The order of closure was randomized. Measurements-WBS was measured after wound closure with a validated vacuum-controlled wound chamber device (BT-2000) that measures the pressure required to disrupt the closed wound. Data analysis-between-group comparisons were performed with pair-wise t-tests and chi-squared tests. This study had 80% power to detect a 75-mm Hg between-group difference in WBS (two-tailed alpha = 0.05). RESULTS We evaluated 30 incisions in 15 rats. The mean WBS of octyl-cyanoacrylate (298 +/- 58 mm Hg) was significantly higher than that of butyl-cyanoacrylate (199 +/- 87 mm Hg; difference 98 mm Hg [95% confidence interval (CI) 32-165], p = 0.006) or Steri-Strips (129 +/- 67 mm Hg; difference 169 mm Hg [95% CI 112-227], p < 0.001). The WBS of butyl-cyanoacrylate was stronger than that of Steri-Strips; difference 71 mm Hg (95% CI 4-138), p = 0.035. CONCLUSIONS Octyl-cyanoacrylate tissue adhesive has a higher WBS than butyl-cyanoacrylate, whose WBS is greater than that of surgical tape.

Healing of mid-dermal burns in a diabetic porcine model.

Wound healing is delayed in diabetic patients. We developed a diabetic-porcine burn model and compared the healing of partial-thickness burns in normal and diabetic pigs. We hypothesized that wound healing would be delayed in the diabetic swine. Diabetes mellitus was chemically induced in three domestic pigs (25–50 kg) by intravenous injection of streptozotocin 130 mg/kg over 30 minutes. Glucose levels were maintained between 250 and 500 mg/dl by injecting short-acting or long-acting insulin 1 unit/kg daily as needed. Three weeks later, 14 partial-thickness burns were created on the backs and flanks of each of the anesthetized pigs with a 2.5 × 2.5-cm aluminum bar preheated to 80°C and applied for 20 seconds. A similar number of burns were created on three control nondiabetic pigs. The burns were treated with a topical antibiotic, and 3-mm full-thickness biopsies were taken from all wounds at 7, 10, 14, and 21 days for histomorphologic evaluation using hematoxylin and eosin staining by a board-certified dermatopathologist masked to the type of pig. The main outcome was the percentage of the wound in cross section that was reepithelialized. Comparison of outcomes between normal and diabetic pigs was performed with Student’s t-tests. The diabetic pigs gained less weight, and their skin was considerably thinner than in the control pigs. Although the absolute depth of the burns was similar, the relative depth was greater in the diabetic pigs. The percentage of wound reepithelialization was lower in diabetic than in normal pigs at 7 days (1.8% [95% CI: 0–5.5] vs 65.0% [95% CI: 54.2–75.9]; P < .001) as well as at 10 days (19.2% [95% CI: 6.0–32.4] vs 76.9% [95% CI: 59.8–94.0]; P < .001) and 14 days (43.9% [95% CI: 30.4–57.4] vs 99.9% [95% CI: 92.6–100]; P < .001). All burns were completely reepithelialized at 21 days, and none of the wounds were infected. Reepithelialization of partial-thickness burns is delayed in streptozotocin-induced diabetic pigs when compared with normal pigs. It is unclear whether the delay in healing is due to the thinner skin or the metabolic consequences of diabetes or their combination.

Rosiglitazone, a PPAR-γ Ligand, Reduces Burn Progression in Rats

Burns induce the activation of an inflammatory cascade that generates reactive oxygen radicals and lipid peroxidation leading to burn wound progression and extension. Peroxisome proliferation-activated receptor-gamma is a nuclear hormone receptor that is activated by transcription factors and plays an important role in the regulation of cellular proliferation and inflammation. We hypothesized that treatment of burns with rosiglitazone, a peroxisome proliferation-activated receptor-gamma ligand, would reduce burn wound progression. This is a randomized controlled study of 20 Sprague-Dawley rats. Two burns were created on each animal’s dorsum using a brass comb with four rectangular prongs preheated in boiling water and applied for 30 seconds resulting in four rectangular 10 × 20 mm full thickness burns separated by three 5 × 20 mm unburned interspaces (zone of ischemia). Animals were randomized to rosiglitazone 4 mg/kg or vehicle by oral gavage 30 minutes after injury and at 24 and 48 hours after injury. Wounds were observed at 1, 2, 3, and 4 days after injury for visual evidence of necrosis in the unburned interspaces. Full thickness biopsies from the interspaces were evaluated with hematoxylin and eosin staining 7 days after injury for evidence of necrosis. The percentage of interspaces that progressed to necrosis was compared with &khgr;2 tests. Forty comb burns with 120 unburned interspaces were evenly distributed between rosiglitazone and vehicle. The number of interspaces that progressed to full thickness necrosis at 1, 2, 3, 4, and 7 days after injury in the rosiglitazone and vehicle groups were 9/60 (15%) versus 13/60 (21%) (P = .48), 16/60 (27%) versus 15/60 (20%) (P = 1.00), 24/60 (40%) versus 46/60 (77%) (P = .001), 35/60 (58%) versus 53/60 (88%) (P = .001), and 43/60 (72%) versus 54/60 (90%) (P = .02), respectively. Treatment with oral rosiglitazone reduces the percentage of unburned skin interspaces that progress to full necrosis in a rat comb burn model.

The effect of cyclodextrin-solubilized curcuminoids on amyloid plaques in Alzheimer transgenic mice: brain uptake and metabolism after intravenous and subcutaneous injection

IntroductionCurcuminoids may improve pathological conditions associated with Alzheimers disease. However, their therapeutic potential is limited by their exceedingly low bioavailability after oral administration. A method to deliver solubilized curcuminoids by injection was evaluated in Alzheimer transgenic mice.MethodsAmyloid protein precursor (APP)SWE, PS1dE9 mice were intravenously or subcutaneously injected at weekly intervals between the ages of 4 and 12 months with serum- or cyclodextrin-solubilized curcuminoids to assess their potential for plaque prevention. Alternatively, mice between the ages of 11 and 12 months were intravenously injected with cyclodextrin-solubilized curcuminoids at biweekly intervals to evaluate their ability to eliminate existing plaques. Plasma and brain levels of curcuminoids and their metabolites were also determined after subcutaneous and intravenous injection.ResultsWeekly long-term injections did not result in a significant plaque load reduction. However, intravenous injection of cyclodextrin-solubilized curcuminoids at higher curcuminoid concentrations and at a biweekly frequency between the ages of 11 and 12 months reduced the plaque load to approximately 70% of the control value. After intravenous injection, plasma levels of 100 μM curcuminoids and brain levels of 47 nmol/g could initially be achieved that declined to essentially undetectable levels within 20 minutes. The primary curcuminoid metabolites in plasma were the conjugates of glucuronide or sulfate and hexahydrocurcuminoids as reduction products. In the brain, both hexahydrocurcuminoids and octahydrocurcuminoids were detected as major metabolites. After subcutaneous injection, maximal curcuminoid plasma levels of 23 μM and brain levels of 8 nmol/g were observed at 30 minutes after injection and curcuminoids remained detectable for 2 to 3 h.ConclusionCurcuminoids are rapidly metabolized after injection and their effect on reducing plaque load associated with Alzheimers disease may be dependent on the frequency of administration.

Controlled mild hypothermia prolongs survival in a rat model of large scald burns.

OBJECTIVES Early surface cooling of burns reduces pain and depth of injury and improves healing. However, there are concerns that cooling of large burns may result in hypothermia and worsen outcomes. In contrast, controlled mild hypothermia improves outcomes after cardiac arrest and traumatic brain injury. The authors hypothesized that controlled mild hypothermia would prolong survival in a rat model of large scald burns. METHODS Thirty-six Sprague-Dawley rats (250-300 g) were anesthetized with 40 mg/kg intramuscular ketamine and 5 mg/kg xylazine, with supplemental inhalational isoflurane as needed. A single full-thickness scald burn covering 40% of total body surface area was created on each of the rats using a Mason-Walker template placed in boiling water (100 °C) for a period of 10 seconds. The rats were then randomized to hypothermia (n = 18) or no hypothermia (n = 18). Core body temperature was continuously monitored with a rectal temperature probe. In the experimental group, mild hypothermia was induced by applying ice packs over the prone rats until their rectal temperature was reduced by 2 °C for a period of 2 hours. After 2 hours of hypothermia, the rats were rewarmed back to their baseline temperature with a heating pad. The control rats were not cooled. The rats were monitored until death or for a period of 7 days, whichever was greater. The primary outcome was time to death. The difference in survival between the groups was determined using Kaplan-Meier analysis and the log-rank test. RESULTS   Hypothermia was induced in all experimental rats within a mean of 22 minutes (95% confidence interval [CI] = 17 to 27). The numbers of nonhypothermic and hypothermic rats that were dead at each time point were as follows: 2 hours, five versus none; 18 hours, 16 versus five; 24 hours, 18 versus eight; and 48 hours, 18 versus 13 (p = 0.05). There were no additional deaths after 48 hours. The mean time to survival of the hypothermic rats was significantly greater than that of the nonhypothermic rats (p < 0.001). CONCLUSIONS Induction of brief, mild hypothermia prolongs survival and increases the survival rate in nonresuscitated rats with large scald burns.

Indentation to Probe Atelectasis in Mammalian Lung

Of all the internal organs, mechanical behavior of the lung is arguably most closely related to physiologic function. In inflation and deflation, lung parenchyma may be treated as an elastic material with some viscous damping. However, quasi-plasticity is observed, in the form of atelectasis, which is the localized collapse of alveoli under different conditions. General anesthesia in lung is known to increase tendency for pulmonary atelectasis, and this condition is typically removed by mechanical inflation to high pressures, which can be hazardous. The specific mechanisms of atelectasis are not fully known, one reason for this being the difficulty in developing a direct characterization method to perform causal investigations. In a previous abstract, we described the potential for controlled indentation tests to probe atelectatic tendency in lung. In this talk, we present the first results of ‘hardness testing’ on dog and rabbit lung, using different inflation schemes. Specifically, we indented excised lungs at physiologic pressures, inflated with air, pure oxygen, and 0.2% isoflurane in oxygen. Between these three conditions, we found marked differences in ‘hardness’ of the lung, when indented with tip radii comparable to that of ribs. That is to say, large contrasts in residual impressions, as well as re-inflation behavior, were observed. In addition, effects of different inflation gases occurred within a much shorter time than previously reported in other surgical experiments, indicating perhaps different, faster mechanisms controlling atelectasis than previously considered.

Bronchial Thermoplasty by Application of Ultrasound Energy

Background: Asthma is a chronic inflammatory disease of respiratory airways, typically marked by spasms in the bronchi of the lungs, causing difficulty in breathing. Although the disease is very well documented, therapies are limited and patients mostly undergo symptom management. Bronchial thermoplasty is a radiofrequency-based treatment for severe asthma approved by Food and Drug Administration (FDA) in 2010 (Alair system, Boston Scientific Inc). Here we propose the use of ultrasound (US) energy to perform bronchial thermoplasty. Our hypothesis is that ultrasound affects bronchial smooth muscle at least as effective as radio-frequency (RF) but causes less collateral damage, and holds the potential to reduce the procedure time. In this publication we present a direct comparison of acute thermoplasty effects of RF energy versus ultrasound energy. Objective: To evaluate a bronchoscopic procedure based on circumferential ultrasound energy and its effect on bronchial wall structures in comparison to RF thermoplasty for asthma treatment. Methods: This is an observational study aiming for a direct comparison of an ultrasound system with existing asthma therapy based on radio-frequency. Mongrel dogs were used for optimization of ultrasound energy (300 J, 200 J, 100 J) with a 4.5 and 5.5 mm balloon catheter. 100 J was ultimately directly compared with RF effects on bronchial wall structures. Safety and efficacy of the ultrasound system was already previously established during renal denervation clinica stdies. Results: 12 mongrel dogs were used. Bronchoscopy procedures were feasible in all cases, and no adverse effects were seen in any dogs. Lungs were collected for histology and H&E staining. With the optimized 100 J ultrasound energy we observed mild bronchial tissue injury, with minimal hemorrhage and preservation of respiratory epithelium. The RF catheter caused distinct focal injury points resulting from direct contact of the RF electrodes with bronchial wall tissue. Acute histological examination shows hemorrhagic injury along the RF energy path with significant necrosis to all bronchial wall elements including respiratory epithelium. Conclusion: Ultrasound energy is safe, feasible, and at least as effective in affecting bronchoconstriction as RF energy offering a viable alternative to radiofrequency-based lung disease treatments.