Use of 2-octyl cyanoacrylate adhesive in rat liver induced lesion 1 Uso adesivo de 2-octil cianoacrilato em lesão induzida de fígado de ratos

PURPOSE: To evaluate  the healing process of  rat  traumatic  liver  lesion corrected with  the use of 2-octyl cyanoacrylate adhesive, compared to the use of biologically absorbable chromed catgut thread suture. METHODS: Thirty mail adult rats were divided into two groups (15 per group) according to the used method for liver lesion correction as follows: adhesive group (AG), and catgut group (CG); each group being divided into three subsets of five animals (7th, 14th, and 21st day), respectively, according to post-surgery evaluation. All animals were submitted to homogeneous lesion applying synthetic bonding to AG and using chromed catgut suture to CG for lesion correction. Macroscopic and microscopic parameters of healing processes were evaluated. RESULTS: Both  groups  of  animals  showed  excellent  abdominal  wall  healing,  with  no  evidence  of  infection,  and  no  abdominal cavity peritonitis or abscess. The presence of adherence was observed in both groups with no statistically significant difference. As to macroscopic evaluation, there was statistically significant difference with respect to specific factors of clinical inflammation (ischemic inflammation and giant celular inflammatory reaction) between animals evaluated on the 10th day (ischemic necrosis and giant celular inflammatory reaction) among animals evaluated on the 14th day (A14 versus C14). CONCLUSION: Applying  2-octyl-cyanoacrylate  adhesive  for  correcting  rat  liver  lesion  does  not  change  healing  process  when compared to the use of chromed catgut stitch.


Introduction
The abdominal cavity holds most of the digesting organ system as well as the adjunct glandules, being part of the urogenital system and autonomous plexus 1 .The increasing urban violence coupled with driving accidents has increased abdominal trauma incidence. Being the major abdominal human cavity glandule, the liver is a main lesion target. Therefore, liver traumatism is quite frequent, accounting to a high mortality rate 2 .
Liver trauma merits special attention as to its diagnosis and management. It is assumed that around 45% of closed abdominal trauma and 40% of open abdominal traumas involving the liver. Regarding closed abdominal trauma 84% due traffic accidents followed by 8% trauma by falling, and 2% by physical attack 3 .
Though presenting under several aspects, most liver traumas provoke small liver lesions that at times do not need specific management and when they do, they are solved with minor procedures. Liver lesions can be treated in several manners depending on their severity varying from simple stitching, drainage, regradas and widening resections, or even transplant. In spite of hospital improved infrastructure, aseptic means, material, technical and anatomical know-how, mortality rate is still elevated for subjects with lever lesions, though such organ is protected by the costal gradil 4,5 .
Lately, several treatment alternatives have been tried for liver lesion such as collagen haemostatic agent application, cellulose gelatin, as well as the use of base synthetic bondings diffused in spleen and digestive system, notably in experimental studies 6 .
There is scant information in the literature referring to this bonding use in parenchimatous bleeding. Aiming at collecting more information, we set out to study the use of 2-octyl cyanocrylate in rat liver provoked lesions to evaluate the healing process of the target organ lesions, comparing the use of the bonding agent with the long traditional chromed catgut suture, to evaluate both microscopic and macroscopic aspects.

Methods
The project was evaluated and approved by the by where the light-dark cycle was 12 hours and humidity was the same as a normal environment without any artificial regulation.
The temperature was a constant 20 ± 2ºC. The animals were fed standard commercial food and had free access to water throughout the experiment.
An anesthetic by an intramuscular injection of 0.2ml/100g of weight from a mixture of 1ml of ketamine (50mg) and 1ml of xylazine (20mg). The trychotomy of the ventral abdominal wall was done and anti-sepsis with polyvinylpyrrolidone-iodine.
The surgical procedure consisted of a median laparotomy with four centimeters. The injury in the liver was done at 2.5cm from the peritoneal reflection, followed by simple synthesis with catgut cromate (two stitches) on the catgut groups and synthesis with cianocrilate adhesive and adhesive groups. We then moved on to the laparorraphy at two levels: the first, peritonealmuscularaponeurotic; the second, of the skin, with continuous synthesis, utilizing 5.0 monofilament nylon (Figures 1 and 2).  After recuperating from the anesthetic, the rats were returned to their cages, where they had free access to standard commercial food and water. Immediately after surgery they were given an intramuscular dose of sodium diclofenac at a dosage of 10 mg/kg, as an analgesic and anti-inflammatory drug.
The animals were divided in two groups: adhesive group  After this evaluation, the surgical parts were opened lengthwise and extended on filter paper and set in 10% formalin and forwarded for histopathological study.  (Table 1).

Microscopic evaluation
Acute inflammation intensity was markedly accentuated for the C7 and discrete on the A7 with no statistically significant difference, p=0.250. It showed to be moderate on the 14th day for the CG and largely discrete for the AG; on day 21st it showed predominantly moderated on both evaluated groups. There was no statistically significant difference between the two groups neither on the 14th or 21st day with p=0.117 and p=0.676, respectively (Table 2). Chronic inflammation intensity was largely absent on the C7, discrete and moderate on the A7 with no statistically significant difference, p=0.296. It was absent in most animals from the C14, whereas there was a discrete intensity on the A14 with no statistically significant difference, p=0.117. On day 21st it presented predominantly discrete for both CG and AG with no statistically significant difference, p=0.403 (Table 3).

Discussion
Due to its easy availability, handling and accommodation, resistance to manipulation, surgical aggression, and to infectious processes, the rat was used for evaluation of liver healing course.
In the present study the animals were divided into two Simple suture with chromed catgut 4-0(Ethicon ® ) thread was used on the catgut group (CG) lesion, the choice being made because of its widespread use for correcting liver trauma lesions, thus observing adequate lesion haemostasia with no perceptive differences with respect to the adhesive group 9 .
As to macroscopic evaluation the presence of abdominal cavity bondings was not seen in the greater majority of animals where the bonding was used, contrasting with studies, where increased intra-cavity bonding was found 11 . We observed, however, statistically significant difference between the subgroups A7 and C7, with a lower bonding incidence for the A7 group.
Inflammation is divided into chronic and acute standards.
Acute inflammation has a relatively short duration, varying from hors to a few days, and its main aspects are fluid and plasmatic protein exudation and the emigration of leukocytes, neutrophils predominately. On the other hand, chronic inflammation has longer duration and it is histologically associated to the presence of lymphocytes and macrophages, blood vessel proliferation, tissue fibrosis and necrosis. Therefore, we opted to use the very same protocol used for the histological evaluation of the study pieces, excluding the reepitelization, coaptation of suture edges, and wall infiltrate extension items, present in the original protocol 14 .
It is assumed that acute inflammation characterizes the stage 1 or inflammatory phase of the healing process upon healing evaluation, whereas indicators for chronic inflammation correspond to stage 2, or proliferative phase of healing process 15 .
Hematoxylin-eosin dyeing was used in the present study to evaluate the proposed parameters 9 . However, the degree of fibrosis (collagen) was evaluated by Trichrome of Massom dyeing, not performing, nonetheless, the identification and quantification of collagen type.
The inflammatory reaction intensity degree could be of uttermost importance for the healing process, since the quantity of polymorphonuclear (PMN) in the wound has a close relationship with proliferation, activation and cellular movement, and the production of inflammatory process mediating cytokines 16 .
When evaluating histological changes in liver fragments on the respective groups, and comparing the groups with their respective dates of observation, one can notice statistically significant difference only on evaluating specific aspects of chronic inflammation (ischemic necrosis and alien body type giant celular inflammatory reaction between the A14 and C14 groups, where there was an increase of those parameters in the C14 group with respect to the A14 group. Both with respect to acute inflammation and chronic inflammation, we did not observe statistically significant difference between the two groups as to the other inter-group parameter evaluation.
Both for acute inflammation assessment and chronic inflammation parameters an average variance between mild and moderate within the described evaluation periods was observed, thus favoring the adequate healing process since the absence or excessive inflammatory response markedly compromises tissue healing.
Upon intergroup (A7 versus A14 versus A21 and C7 versus C14 versus C21) assessment, statistically significant difference was observed only for the catgut group when fibroblastic proliferation and capillary neo-formation were studied, contrasting with what was expected for both groups, which would be a decreased acute inflammatory intensity, and temporal progression of the chronic one.

Conclusion
Applying 2-octyl-cyanoacrylate adhesive for correcting rat liver lesion does not change healing process when compared to the use of chromed catgut stitch.