CONTRIBUTIONS OF NURSES IN BASIC RESEARCH: DRESSING FIXATION MODEL FOR EXCISIONAL CUTANEOUS WOUNDS OF MICE

Objective: validate method of fixation of dressings on excisional cutaneous wounds of mice. Method: preclinical study. Sample made up of animals of the C57BL/6 strain, which had two excision wounds made in the dorsal region. Different methods and products, widely accepted in clinical practice, for fixing dressings in the animal model were evaluated. The evaluated outcomes were the length of stay of the dressing and the occurrence of adverse events. Results: crepe bandage, microporous tape and self-adhesive bandage had a shorter residence time when compared to polyurethane film. This, in turn, varied the time when comparing different marks (E, F, G and H) and number of turns around the animal’s body. With 1 lap, the time varied from <24 to 36 hours. With 2 laps, the marks E and G remained 48 and 96 hours, respectively, and F and H time <24 hours. G-brand film, cut to size 3 cm x 15 cm, giving the mouse body 2 turns, kept the dressing for 96 hours. The skin remained intact, with no adverse event. Conclusion: a dressing fixation model for wounds in mice was created with a product available in Brazil and compatible with the animal’s body structure. DESCRIPTORS: Healing. Bandages. Basic research. Stomatherapy. RESUMEN Objetivo: validar método de fijación de apósitos en heridas cutáneas excisionales de ratones. Método: estudio preclínico. Muestra compuesta por animales del linaje C57BL/6 que tuvieron dos heridas excisionales confeccionadas en la región dorsal. Se evaluaron distintos métodos y productos, ampliamente aceptados en la práctica clínica, para fijación de apósitos en el modelo animal. Los resultados evaluados fueron tiempo de permanencia del apósito y ocurrencia de eventos adversos. Resultados: La venda de crepé, la cinta microporosa y el vendaje autoadherente presentaron menor tiempo de permanencia cuando comparados con la película de poliuretano. Esta, a su vez, varió en el tiempo cuando comparadas distintas marcas (E, F, G y H) y número de vueltas alrededor del cuerpo del animal. Con una vuelta completa, el tiempo varió de menos de 24 a 36 horas. Con dos vueltas, las marcas E y G permanecieron 48 y 96 horas, respectivamente, y F y H, tiempo igual e inferior a 24 horas. La piel permaneció íntegra, sin evento adverso. Conclusión: se creó un modelo de fijación de apósitos en ratones con un producto disponible en Brasil y compatible con la estructura del cuerpo del animal.


INTRODUCTION
Basic research can contribute to solving problems inherent to nursing care 1 when the research results allow its translation into clinical practice 2 . The development of experimental model research by nurses becomes relevant, as it is possible to materialize reality and support the effect of nursing interventions. It is noteworthy that the animal model allows the evaluation of biological phenomena, which can be compared to humans 3 ,with an emphasis on translational research.
Animal experimentation allows the understanding of knowledge gaps related to physiological and pathological processes, which can impact clinical nursing practice. There is variability in experimental studies that address the healing of skin wounds, but, contradictorily, these studies are conducted by other professional categories 4,5 . Such an issue may limit the implementation of nursing interventions in the treatment of wounds in the context of in vivo research.
In nursing, there is still a debate about the relevance of the use of animals in research on themes in this area of knowledge 3 . However, some studies started to be produced in the area, especially those aiming at the integration of basic science to the contents of tissue repair of wounds 6,7 . It is believed that the use of available technologies for the treatment of skin wounds can be improved by Nursing through the development of experimental and clinical research 8 . In this way, the effects of these products on the different stages of the skin wound healing process will be explained. In this context, doubts persist about the adequate fixation of the dressing to the animal skin.
The term dressing fixation, in this study, represents the act of applying a product to maintain primary coverage over the wound. It is understood that the fixation of a dressing must be able to guarantee the maintenance of the cover over the wound bed for a certain period of time, preserving and protecting the wound against possible trauma. Therefore, in order to carry out studies on the treatment of wounds in animals, especially mice whose nature is restlessness and the ability to remove everything applied to their back, the first step is to establish a dressing fixation model consistent with clinical nursing practice.Thus, the aim of this study is to validate a method of dressing fixation on excisional skin wounds of mice. The different types of fixation tested were repeated at least five times until they were considered inappropriate or appropriate. Next, two animals were used to test the crepe bandage, two for microporous tape, two for self-adhesive bandages and four animals for polyurethane film. The animals were submitted to anesthesia at each dressing change.
Crepe bandage, microporous tape, self-adhesive bandage and polyurethane film were cut into strips approximately The study also evaluated the size of the cover to be applied to the excisional wound made with a 5mm surgical punch. The evaluation included the application of a 1 cm² plate dressing (one for each wound) and in a single rectangular shape, with the following dimensions: 1 cm long by 2 cm wide, to cover the entire area of the 2 wounds and ensure a small margin of overlapping of the skin around them.
Data collection took place in the first half of 2019. The study involved a sample of ten animals, which underwent five days of setting and adaptation before the excisional wound was applied and the dressing was applied. The animals were anesthetized with xylazine 2% at a dose of 10mg/kg and ketamine 10% at a dose of 100mg/kg (manufacturer Syntec), prepared in sterile 0.9% saline and administered intraperitoneally. Subsequently, these animals were submitted to trichotomy and asepsis of the dorsal region. The trichotomy was performed with a Wall® mini-trichotomizer, a portable model. Skin asepsis was performed with 70% alcoholic solution.
In each animal, two excision cutaneous wounds were performed in the middle region of the dorsum with the aid of a 5 mm diameter dermatological surgical punch. All skin tissue was removed, including epidermis, dermis, hypodermis and fleshy panicle. The wounds were made with a minimum distance of approximately 0.5 cm and a maximum of 1.0 cm between them 9 .
Then, coverage was applied over the wound and the dressing to be evaluated was fixed. The application followed the dressing fixation model 10 .The fixation was applied around the body of the mouse, in order to make one or two complete turns around the animal.
The integrity and maintenance of the fixation employed were evaluated every two hours for the first six hours after the end of the anesthetic effect, and every three hours for the subsequent six hours. After 12 hours from the beginning of the experiment, the evaluations were carried out every 6 hours until the dressing was partially or completely released. At the end of the experiment, the region around the wound was inspected to assess the integrity of the skin and identify adverse events.
During the study, the animals were kept in an exclusive room to house these animals, under controlled conditions of temperature (24° C), light (12 hours light/dark cycle), in individual cages (polypropylene box with an approximate size of 25 cm³) , with a distance of 5 cm (horizontal) and 60 cm (vertical) between them. The animals had free access to food and water, and the cages were cleaned twice a week to prevent the accumulation of ammonia in the environment.
At the end of the experiments, all animals were euthanized with overdose of anesthetic 2% xylazine at a dose of 30mg/kg and ketamine 10% at a dose of 300mg/kg, both prepared in sterile 0.9% saline, administered intraperitoneally, followed by cervical dislocation, according to the Brazilian guide of good practices for euthanasia of animals, Resolution

RESULTS
The dressing fixation time varied from 1 to 96 hours, according to the type and brand of the product (Table 1). The application of the crepe bandage, the self-adhesive bandage and the microporous tape was illustrated in Fig. 1. The crepe bandage was wrapped around the animal's body and the tip fixed with adhesive tape to simulate the reality of clinical practice (technique A) and with suture stitches (technique B). In both forms, the dressing time on the wound did not exceed 1 hour and 30 minutes.
The self-adhesive bandage was applied in two different ways, one by means of tactile pressure (technique A). However, it was not possible to apply adequate pressure to adhere to the bandage due to the mouse's body structure, which does not resist the tactile pressure necessary for self-adherence of this bandage. In the other way, the bandage was applied around the animal's body and sutured with a cotton thread in the proximal and distal portions (technique B). However, it was observed that the animal was able to sneak out of the tubular structure formed by the bandage. In the five attempts made in this modality, the dressing time in the wound bed did not reach five hours.
When fixing the dressing with microporous tape marks C (3M®) and D (Cremer®), the residence time was, at most, two hours for the two marks evaluated. The animals were able to chew the tape on the lateral regions and, with that, expose the primary cover and the wounds.
The use of the polyurethane film as a secondary covering was illustrated in Fig. 2 and the sequence of application of it was demonstrated in Fig. 3, as primary covering (a to d) and secondary covering (a' to d'), respectively. were applied with a complete loop around the animal's body. This type of fixation allowed the animals to gnaw on the film until it broke, with exposure of the covering and the wound. The dressing time was up to 36 hours for the E and G brands, and less than 24 hours for the F and H brands.
The same marks of polyurethane film were applied giving two complete turns around the animal's body. The dressing time was longer for the E (Systagenix®) and G (3M®) marks, with 48 and 96 hours, respectively. The brands F (Smith & Nephew®) and H (Curatec®) had a time of 24 hours and less than 24 hours, respectively.
The evaluation of the coverage for application on the wounds confirmed that the rectangular shape in the dimension of 1 cm long by 2 cm wide (vertical x horizontal) showed better performance for maintaining the dressing on the wound bed.
In this experiment, no adverse events were observed on the skin around the wounds. The applied dressings were maintained and observed until the animal itself removed them or there was loss of adhesion (natural detachment) of the dressing. This positioning considered that the objective of this study was to evaluate the duration of the dressing on the wounds, so there were no interventions, such as removal or punctual change of the dressing.
The results made it possible to establish recommendations for the adoption of the dressing fixation model ( Table 2). Table 2. Standardizations for making an excisional wound, applying and fixing dressings. Belo Horizonte (MG) − 2020.

Standardized variable Results
Place The mouse was chosen for this study because it is the most commonly used animal model, especially in studies of physiology and biochemistry, as they are easy to handle and maintain, in addition to being economically accessible. They can be standardized by age, sex, history and genetic predisposition, and allow the use of a relatively high number of animals for statistical validationHow to cite. However, the mouse has a small body, which makes it difficult to fix and maintain the dressings when assessing wound treatment.
Contributions of nurses in basic research: dressing fixation model for excisional cutaneous wounds of mice The middle dorsal region was defined as the best place for making excision wounds in mice of the C57BL/6 strain due to the physical constitution of these animals, corresponding to the largest area for the application and adhesion of dressings. It was also delimited that two wounds would be made on the backs of these animals so that the application and fixation of the dressing would occur more closely to the biophysics involved in the treatment of wounds. In addition, it was defined that the minimum distance between the wounds would be 0.5 to 1.0 cm in both directions (vertical and horizontal), especially when it comes to studies that involve making a number of excisional wounds ≥ to 2 9 . The evaluations demonstrated that the application of a single block covering (1cm x 2cm rectangle) was the most appropriate technique, as it allowed the occlusion of the wound area and ensured a small margin of exposed skin around the wound, reducing the time required for application. of the cover and fixation of the dressing, facilitating the handling of the cover and, consequently, reducing handling and stress of the animal.
The model of excision cutaneous wounds used as a reference, which establishes the making of four wounds on the dorsum of the mouse 9 , is reproducible, in addition to being widely accepted for the study of skin wounds. Likewise, the amount of wounds to be made is directly proportional to the amount of material needed for histological and/or immunohistochemical analyzes proposed.
Thus, the adaptation of this model to two wounds contributes to the maintenance of the animals' well-being during the experiment, as its spoliation is reduced by 50% and the possibility of discomfort and pain is less than in the model of four skin wounds.
At the end of this study, it was defined that the best fixation of the dressing is that made with transparent non-sterile polyurethane film of the G (3M®) brand, measuring 3 cm in length by 15 cm in width, applied over the primary covering or over the different types of wound care products.
The dimensions of the polyurethane film that allowed the application in two complete rounds around the mouse body ensured a longer dressing time (96 hours) when compared to just one round, which allowed a time of up to 48 hours. In addition, the length ensures that the polyurethane film is applied to the animal in order to overlap the primary cover used, ensuring a safety margin for the product's adherence to the animal's skin.
There are a large number of studies developed in experimental models 12,13 . However, these models used to evaluate wound treatment do not fully contemplate the principles of ideal dressing. Many are not able to provide an adequate environment for healing and materialize the reality of clinical practice.
The products used in the study for fixing dressings are routinely adopted by professionals in clinical practice. The choice of these products was directly related to the location of the wound and the characteristics of the product used to treat it.
Some experimental studies in murine models do not mention or describe the methods used clearly for the application and fixation of the dressing 14,15 . The main challenges for replicating these studies are gaps in information and variations in the way of applying the products investigated by the researchers.
Among the published experimental studies, some have described ways of fixing dressings in animal models 10,16,17 that served as support and guidance for the standardization of the dressing model used in this study in question.
A study 16  In another study 18 the silicone dressing was sutured with nylon threads to evaluate the healing of excisional skin wounds in animals with induced chronic kidney disease. Immediately after applying this plate, polyurethane film (3M) was applied as secondary dressing. The tissue from the wounds was collected at 3, 7 and 14 days after its preparation, when the fixation was removed. This polyurethane film was the same as in the study that managed to keep the dressing in place for 96 hours, when used with two turns on the mouse's body.
Another study also used the suture to maintain dressing over the wound 10 . There is a description of the fixation of a gel composed of platelet-rich plasma in the topical treatment of surgically induced second and third degree burns. The gel was applied over the lesion and fixed by means of a semi-rigid plastic disc attached around the wound with surgical stitches. Then, the researcher wrapped the animals' chest with adhesive tape to avoid removing the dressing by them. The suture of the disc was maintained for 5 days and after that period no dressing was applied to the wounds.
As in the aforementioned studies, in this research, the proposal for secondary coverage through the use of polyurethane film was adopted. However, the suture was excluded to keep the dressing on the wound, as this practice can interfere with the healing process as it is a source of trauma during its performance. In addition, each dressing change requires making a new suture.
Fixation with polyurethane film was tested, evaluated and adjusted for two turns on the animal's back, making it possible to standardize the fixation of dressings in the studies carried out by the researchers to evaluate the treatment of wounds in an animal model (mouse).
For making the wounds, the criteria regarding the location and size of the wound were maintained. It was considered that the 5 mm surgical punch is sufficient to make the wound and remove the tissue. Regarding the location, it was found that the more centralized the wound disposition (middle dorsal region), the greater the possibility of adhesion and fixation of the dressing. Such facts facilitate the application of the covering and the fixation of the dressing on the mouse.
The polyurethane film can be used as a primary covering to promote occlusion of the lesion or as a secondary covering, that is, to fix the applied dressing. The results achieved during the dressing fixation standardization experiment are similar to the procedures performed by professionals in clinical practice for fixing dressings on the wounds subjected to treatment.
Chronic wounds are more similar because they require frequent dressing changes over a long period of time. This characteristic requires greater care from professionals to implement care aimed at maintaining the integrity of the skin around the wound, where the dressings are adhered.
Despite the progress in translational research on skin wound healing in the past few decades, no animal model fully predicts all clinical outcomes 11 . However, the standard for dressing fixation is essential to ensure that the chosen treatment remains on the wound on the mouse's back for the prescribed time, in addition to preserving the integrity of the skin around the wound.
The experimental model partly materializes the process of dressing changes in the treatment of wounds carried out by nurses in order to assist in the development of new research in the area. It was possible to establish a dressing fixation model in mice with a 96-hour durability with the use of the G (3M®) polyurethane film, cut to size 3 cm long by 15 cm wide, giving two turns in the animal's body. The dressing permanence time meets the demands of the animal experiment segments. Thus, this model will contribute to nurses in fixing dressings in their practice and also during research involving coverage analysis, wound treatment and tissue repair.

CONCLUSION
The study presents an advance in knowledge, since it establishes a dressing fixation model for wounds in mice with a product available in Brazil and compatible with the animal's body structure. In addition, the G (3M®) polyurethane film and the technique of wrapping the mouse's body with two turns were resistant to the movements and action of the animal's teeth.
It is recommended that the proposed fixation model be used by nurses. It must also be expanded to other animals to confirm the effectiveness of the product (polyurethane film) and technique (two turns) with necessary adjustments to the dimension of the film (width x length), according to the size of the wound and its location.