Experimental Models for Controlled Burn Injuries in Rats: A Systematic Analysis of Original Methods and Burn Devices.

Despite a wide variety of models found in literature, choosing the right one can be difficult as many of them are lacking precise methodology. This study aims to analyze and compare original burn models in terms of burn device and technique, parameters, and wound depth assessment. A systematic search was performed according to PRISMA guidelines on studies describing original experimental burn models in rats. The adapted PICO formula and ARRIVE checklist were followed for inclusion and assessment of quality of studies. Characteristics of animals, burn technique, burn parameters, and method of histological confirmation of burn depth were recorded. Twenty-seven studies were included in the final analysis. Most studies used direct contact with skin for burn infliction (n = 20). The rat's dorsum was the most common site (n = 18). Ten studies used manually controlled burn devices, while 10 designed automatic burn devices with control over temperature (n = 10), exposure time (n = 5), and pressure (n = 5). Most studies (n = 7) used a single biopsy taken from the center of the wound to confirm burn depth immediately after burn infliction. From the wide variety of burn models in current literature, our study provides an overview of the most relevant experimental burn models in rats aiding researchers to understand what needs to be addressed when designing their burn protocol. Models cannot be compared as burn parameters variate significantly. Assessment of burn depth should be done in a standardized, sequential fashion in future burn studies to increase reproducibility.

New Chimeric Groin Flap: Experimental Model in Rats.

AIM: Increased emphasis is on using tissue substitutes and stem cells to improve flap applicability and survival rates. To accomplish this, the first step is to have a versatile experimental flap, easy to harvest and use as a template. We sought to develop a reliable experimental chimeric groin flap with free mobility and reliable bloods supply that can be twisted, relocated, and integrated easily with other materials. MATERIALS AND METHODS: Ten male Wistar rats were included. The flap consists of a 2.5-cm skin paddle centered on the medial branch of the inferior epigastric artery and a 4.5/2-cm fat pad supplied by the lateral branch of the inferior epigastric artery. After being raised, flaps were resutured in their anatomical position. Flaps were followed up for 15 days. At the end of the study, the viability of flaps was analyzed by ultrahigh-frequency ultrasound, nontargeted contrast study, and histology assessment. RESULTS: All flaps survived without significant complications. Nontargeted microbubbles spread evenly in both the superficial and deep flap. Ultrasound assessment at day 15 showed no significant areas of necrosis or edema. Histology examination of 3 random flaps confirmed vessel patency and flap viability. CONCLUSION: We propose a simple, easy to harvest and reliable experimental flap which offers a main advantage of all-around mobility through its chimeric design. It is a suitable model for bioengineering studies as it can be used as a template for integration of tissue substitutes or stem cells, between its 2 components.

Role of Ultrahigh Frequency Ultrasound in Evaluating Experimental Flaps.

BACKGROUND: Experimental flap follow-up needs faster, safer, and less invasive techniques that can be easily correlated to clinical procedures. For this reason, we aimed to test the role of ultrahigh frequency ultrasound in follow-up of flap viability. Further on, we aimed to analyze if the chimeric groin flap can be mobilized in a sandwiched position without affecting its vascular supply by twisting its pedicle. METHODS: A total of 12 male Wistar rats, split into three groups, were used. Group A (n = 4) had the chimeric groin flap repositioned in a sandwich position on the anterior abdominal wall and underwent ultrahigh frequency ultrasound follow-up at days 10 and 14. Group B (n = 4) also had the flaps sandwiched, however, at day 14 the vascularity of flaps was proven by infusion of nontargeted ultrasound contrast agents, after which flaps were sent for histological analysis. Group C (C1 n = 2, C2 n = 2) was the control group. In C1 the chimeric groin flap was harvested and sent for histology on day 0, acting as a histological benchmark of flap viability, and in C2 the chimeric groin flap was re-sutured in its anatomical position and after 14 days, flaps were harvested and sent for histological analysis, acting as a direct control for Group B. RESULTS: Ultrasound showed constant vascular flow in both adipose and skin flaps in the sandwiched position. Microbubble study showed diffuse perfusion within flaps. Ultrasound measurements of flow velocity, flap volume, and percentage of vascularity showed a decrease in flap volume and increase in vascularity over 14 days. Histology showed similar viability in both groups. CONCLUSION: Ultrahigh frequency ultrasound may be a valuable tool for postoperative flap assessment, while the chimeric flap can be moved freely in a sandwich position making it suitable for adding tissue substitutes within its components.

Reduced Renal Mass, Salt-Sensitive Hypertension Is Resistant to Renal Denervation.

Aim: Activation of the sympathetic nervous system is common in resistant hypertension (RHT) and also in chronic kidney disease (CKD), a prevalent condition among resistant hypertensives. However, renal nerve ablation lowers blood pressure (BP) only in some patients with RHT. The influence of loss of nephrons per se on the antihypertensive response to renal denervation (RDNx) is unclear and was the focus of this study. Methods: Systemic hemodynamics and sympathetically mediated low frequency oscillations of systolic BP were determined continuously from telemetrically acquired BP recordings in rats before and after surgical excision of ∼80% of renal mass and subsequent RDNx. Results: After reduction of renal mass, rats fed a high salt (HS) diet showed sustained increases in mean arterial pressure (108 ± 3 mmHg to 128 ± 2 mmHg) and suppression of estimated sympathetic activity (∼15%), responses that did not occur with HS before renal ablation. After denervation of the remnant kidney, arterial pressure fell (to 104 ± 4 mmHg), estimated sympathetic activity and heart rate (HR) increased concomitantly, but these changes gradually returned to pre-denervation levels over 2 weeks of follow up. Subsequently, sympathoinhibition with clonidine did not alter arterial pressure while significantly suppressing estimated sympathetic activity and HR. Conclusion: These results indicate that RDNx does not chronically lower arterial pressure in this model of salt-sensitive hypertension associated with substantial nephron loss, but without ischemia and increased sympathetic activity, thus providing further insight into conditions likely to impact the antihypertensive response to renal-specific sympathoinhibition in subjects with CKD.

Design and Testing of an Experimental Steam-Induced Burn Model in Rats.

BACKGROUND: Most of the current models for experimental burns pose difficulties in ensuring consistency and standardization. AIM OF STUDY: We aimed to develop an automated, reproducible technique for experimental burns using steam-based heat transfer. METHODS: The system developed for steam exposure was based on a novel, integrated, computer-controlled design. Three groups of rats were exposed to steam for 1, 3, and 7 seconds. The lesions were evaluated after 20 minutes, 48 hours, and 72 hours after burn induction. RESULTS: One-second steam application produced a superficial second-degree burn; three-second application induced deep second-degree burn; and seven-second application led to a third-degree burn. CONCLUSION: The high level of automation of our integrated, computer-controlled system makes the difference between our system and other models, by ensuring the control of the duration of exposure, temperature, and pressure and eliminating as many potential human generated errors as possible. The automated system can accurately reproduce specific types of burns, according to histological assessment. This model could generate the reproducible data needed in the study of burn pathology and in order to assess new treatments.

The Effects of Adipose-Derived Stem Cell-Differentiated Adipocytes on Skin Burn Wound Healing in Rats.

Both adipose-derived stem cells (ADSCs) and fat grafting promote burn wound healing, but whether adipogen-derived cells using various inducers such as 3-isobutyl-1-methylxanthine (IBMX) and insulin affect wound healing is unknown. Herein, ADSC-differentiated adipogenic lineages were used in rat burn wounds to evaluate wound healing potential. ADSCs were cultivated using six different adipogenic differentiation conditions (IBMX ± insulin, IBMX for 5 days, high and low Dulbecco's modified Eagle's medium) and in vitro morphological changes and cell proliferations during adipogenic differentiation were recorded. Intermediate burn wounds were inflicted in 15 Wistar male rats. Afterwards, the rats were divided into five groups for subcutaneous injections under the wounds: control; ADSCs; differentiated adipocytes (-IBMX+INSULIN and +IBMX[D1-5]+INSULIN) and fat prepared by Coleman technique. Macroscopic changes and histology were documented for 3 weeks. Repeated measures analysis of variance was performed to analyze cell growth and wound healing with a statistical level set of P < .05. Induction cocktails significantly reduced proliferation and induced lipid droplet accumulation. Conditioning without insulin induced the least lipid accumulation, while discontinuing IBMX generated larger adipocytes (P < .001). Adipogenic differentiated ADSCs had similar wound healing abilities with ADSC and fat injections, but differentiated adipocytes (+IBMX[D1-5]+INSULIN) and fat grafting accelerated the early healing process relative to ADSC (P < .001). Reduced fibrosis and mild inflammatory infiltration limited to superficial dermis were observed in +IBMX(D1-5)+INSULIN and fat injection groups, while those reactions were mild to moderate in ADSC group. Differentiated adipocytes achieve similar wound healing results compared with ADSC and fat injections, but differentiated adipocytes (+IBMX[D1-5]+INSULIN) and fat grafting accelerate early healing relative to ADSC.

New antimicrobial chitosan derivatives for wound dressing applications.

Chitosan is a non-toxic, biocompatible, biodegradable natural cationic polymer known for its low imunogenicity, antimicrobial, antioxidant effects and wound-healing activity. To improve its therapeutic potential, new chitosan-sulfonamide derivatives have been designed to develop new wound dressing biomaterials. The structural, morphological and physico-chemical properties of synthesized chitosan derivatives were analyzed by FT-IR, (1)H NMR spectroscopy, scanning electron microscopy, swelling ability and porosity. Antimicrobial, in vivo testing and biodegradation behavior have been also performed. The chitosan derivative membranes showed improved swelling and biodegradation rate, which are important characteristics required for the wound healing process. The antimicrobial assay evidenced that chitosan-based sulfadiazine, sulfadimethoxine and sulfamethoxazole derivatives were the most active. The MTT assay showed that some of chitosan derivatives are nontoxic. Furthermore, the in vivo study on burn wound model induced in Wistar rats demonstrated an improved healing effect and enhanced epithelialization of chitosan-sulfonamide derivatives compared to neat chitosan. The obtained results strongly recommend the use of some of the newly developed chitosan derivatives as antimicrobial wound dressing biomaterials.

Synthesis and biological evaluation of new 2-azetidinones with sulfonamide structures.

New series of N-(arylidene)hydrazinoacetyl sulfonamides 4a1-6, 4b1-6 and N-(4-aryl-3-chloro-2-oxoazetidin-1-yl)aminoacetyl sulfonamides 5a1-6, 5b1-6 were synthesized. The structures of the new derivatives was confirmed using spectral methods (FT-IR, 1H-NMR, 13C-NMR). The antibacterial activities of these compounds against Gram positive (Staphylococcus aureus ATCC 6583, Staphylococcus epidermidis ATCC 12228, Enterococcus faecalis ATCC 25912) and Gram negative (Klebsiella pneumoniae CIP 53153, Proteus vulgaris CIP 104989, Citrobacter freundii CIP 5732, Enterobacter cloacae CIP 103475, Escherichia coli ATCC 25922, Pseudomonas aeruginosa CIP 82118) bacterial strains were evaluated using the broth micro-dilution method. Compound 4a2 displayed the highest antibacterial activity, especially against Staphylococcus epidermidis, Enterococcus faecalis and Pseudomonas aeruginosa. The antioxidant potential of the synthesized compounds was also investigated according to ferric reducing power, total antioxidant activity and DPPH radical scavenging assays. All tested compounds showed excellent antioxidant activity in comparison with sulfadiazine and sulfisoxazole which were used as parent sulfonamides. Moreover, some of them showed an antioxidant activity comparable with that of ascorbic acid. In general, the compounds designed based on a sulfadiazine skeleton (compounds 4a1-6, 5a1-6) are more active than those obtained from sulfisoxazole (compounds 4b1-6, 5b1-6), and the N-(arylidene)hydrazinoacetyl sulfonamide derivatives 4a1-6, 4b1-6 are more active than their azetidionone analogues 5a1-6, 5b1-6.

Training of microsurgical skills on nonliving models.

Although direct exposure to procedures in the operating theater environment, together with practice on laboratory animals, is still seen as the gold standard of teaching in microsurgery, practice on nonliving simulators is currently being validated as an important educational tool. We reviewed the widely used nonliving training models, together with currently accepted innovations, which are parts of curricula of training courses in microsurgery. Using the experience accumulated in training programs at the Centre for Simulation and Training in Surgery, we identified which particular skills can be reliably targeted by each nonliving tissue exercise. We were able to find five groups of nonliving training models: basic manipulation, knot-tying principles, completing the anastomosis, the real tissue experience, and training in virtual reality. The more abstract models might seem quite far from the real life experience, but they each closely address specific skills. It thus becomes convenient for the instructor to train these skills separately. This generates series of consistently favorable results once the skills are integrated into a more complex procedure. Focused exercises, once assembled in continuity, reconstruct the real life scenario. The training program can comprise a series of increasingly difficult exercises, which mirror the real life situations. Performance on nonliving models in each progressively more challenging exercise can be assessed via direct observation, assisted by clear and objective criteria. Finally, focused training will help both the transition to human surgery and replication of the favorable results to large series of subjects.

Assessment of the microsurgical skills: 30 minutes versus 2 weeks patency.

The aim of this study is to evaluate the amount of training needed by a trainee, with no background in microsurgery, in order to achieve proper skills for microvascular anastomosis. A protocol based on the rat femoral artery was established to provide a quantitative representation. Five inexperienced subjects started performing microvascular anastomosis. Patency was assessed at 30 min. The final assessment was performed at 2 weeks when rats were reoperated and the patency below the anastomosis was checked. The experiment was discontinued for one subject when he/she succeeded to have two series of four anastomosis with 100% patency at 2 weeks. The results were: 47.5% patency rate at 30 min and 7.5% at 2 weeks (series 1-2); 67.5 and 32.5% (3-4); 82.5 and 35% (5-6); 100 and 70% (7-8); 100 and 87.5% (9-10). Two trainees obtained 100% patency at 2 weeks after series 9-10. Other three needed two more series. There is a significant statistic difference (P < 0.01) between the results at 30 min and 2 weeks for the series (1-2, 3-4, 5-6, 7-8). The patency rate at 2 weeks reflects in a better way the microsurgical skills of a trainee. For long term functioning anastomosis, the training period needs an extension beyond that necessary for 100% patency at 30 min.

Loupes-only microsurgery.

Standard magnification in microsurgery is accomplished with the operating microscope. Loupes are perceived by the microsurgical community as technically less safe. However, after several years of microscope-only microsurgery, most of our microvascular procedures are performed under loupes 3.5-4x. Considering our results using loupes-only microsurgery, which are comparable with those obtained when using the microscope, we suggest that loupe-aided microsurgery might represent a natural progression for the experienced microsurgeon. Microsurgical skills and experience outweigh the importance of the magnification factor. While the microscope is mandatory for replantations distal to the palmary arch, microneurosurgery, and supramicrosurgery, loupes should be used in so-called "macro-microsurgery." One may include in this category replantations down to the palmar arch and free flaps with vessels more than 1.5 mm, such as the latissimus, serratus, (para)scapular, fibula, radial forearm, rectus abdominis, dorsalis pedis, omentum, and jejunum. Before starting loupes-only microsurgery, intensive training under the microscope is crucial. Less magnification does not mean less quality.

Vascular access in chronic dialysis: a plastic surgeon's approach.

Thirty-five years after Brescia et al. (N Engl J Med 275:1089-1092, 1966) realized the first peripheral autogenous arteriovenous fistula, the "Achilles' heel" of chronic dialysis is still the absence of a good-quality permanent vascular access. The number of patients depending on hemodialysis is increasing. Until 10 years ago, in Romania, there was a need to treat isolated critical cases. Nowadays, every dialysis center needs algorithms for a standardized approach, adaptable for each case. We reviewed 171 consecutive arteriovenous fistulas (132 patients) performed in adults in identical standard conditions: use of an inflatable tourniquet during the vascular dissection, microsurgical techniques, and use of only autogenous tissues. We analyzed our results, the technical difficulties encountered, and their management in long-term follow-up. The aim of this study was to set up the basic principles of our algorithms. Our approach, based on our education as plastic surgeons involved in hand surgery and microsurgery, might present the advantage of sparing renal patients vascular capital.