Abstract

Background: Postoperative strictures, which are still serious problems of tracheal surgery, are caused by an inflammatory reaction with subsequent edema and granulation tissue formation. Taking this into consideration, we have designed a study in which tenoxicam (potent, non-steroidal, antiinflammatory drug) was used after a tracheal surgery in rats.

Methods: Fourteen female Wistar rats were randomly divided into two groups (tenoxicam and control group) with equal numbers. Ketamine-xylazine anesthesia was performed in the rats. A vertical incision on the anterior tracheal wall, including the third to fifth cartilaginous rings, was performed and closed primarily with an interrupted suture technique using 4/0 absorbable suture. The tenoxicam group was administered 0.5 mg/kg/day tenoxicam and the control group was given 0.5 cc/day 0.9% NaCl via intraperitoneal route for 10 days beginning from the operation day. After two weeks, all animals were sacrificed under general anesthesia. Tracheas were excised, and a pathologist blindly evaluated the cases. The Mann-Whitney U-test was used for statistical analysis, and a value of p<0.05 was considered significant.

Results: The rat specimens were histologically evaluated and scored for inflammatory cell infiltration, angiogenesis, fibroblast proliferation, collagen deposition, and epithelial regeneration. There were meaningful differences in fibroblast proliferation (p=0.036) and epithelial regeneration (p=0.002). These results show that epithelial regeneration was higher and fibroblast proliferation was lower in the tenoxicam group.

Conclusion: Increased fibroblastic activity causes stenosis after tracheal surgery and the application of tenoxicam diminishes fibroblast proliferation and improves epithelial healing. Therefore, postoperative non-steroidal anti-inflammatory drug usage might be a useful therapy in the prevention of stenotic complications after tracheal surgery. However, further studies are needed.

Impaired airway healing and strictures are still serious problems of tracheal surgery. Postoperative narrowing of the tracheal lumen is caused by an inflammatory reaction with subsequent edema and granulation tissue.[1] Although improved surgical techniques and suture materials have diminished the stenotic complications of tracheal surgery, we still have to find a solution to further diminish this complication rate. We think that the solution should be less surgical and more medical.

Considering the inflammatory cause of stricture, we thought that non-steroidal anti-inflammatory drugs (NSAIDs) may prevent or diminish strictures and stenosis after tracheal surgery. Therefore, we designed the current study in which tenoxicam (a potent NSAID) was used after tracheal surgery in rats.

Methods

Fourteen female Wistar albino rats weighing 220-240 g were included in the study. They were randomly divided into two groups: the tenoxicam group (n=7) and the control group (n=7). The animals were anesthetized with 50 mg/kg ketamine hydrochloride (Alfamine, Alfasan Woerden, Holland) and 5 mg/kg xylazine hydrochloride (Alfazyne, Alfasan Woerden, Holland). The anesthetic agents were administered through the intraperitoneal route.

The animals were placed in a supine position. A vertical midline cervical incision was made, and strap muscles were retracted laterally. After exposure of the trachea, a vertical incision was made on the anterior tracheal wall including the third to fifth cartilaginous rings and closed primarily with an interrupted suture technique using 4/0 absorbable (polyglactine) sutures. Any intervention, such as intubation, was not needed for respiration since we did not obstruct the airway during the surgical procedure. After the surgical procedure, the animals were placed under a heating lamp until recovery from anesthesia. For postoperative care, 25 mg/kg/day cefazolin sodium for infection prophylaxis and 2 mg/kg/day tramadol HCL for analgesia were administered intraperitoneally to all animals.

The tenoxicam group had 0.5 mg/kg/day intraperitoneal tenoxicam (Oksamen, Mustafa Nevzat Ilaç Sanayi AŞ, İstanbul, Turkey), and the control group had 0.5 cc/day 0.9% NaCl for 10 days beginning from the day of the operation. After two weeks, all animals were sacrificed under general anesthesia. The trachea was excised from cricoid cartilage to carina with adjacent esophagus. The excised specimens were fixed in 10% neutral buffered formalin solution and embedded in paraffin wax for histological examination. One pathologist blindly evaluated the cases after hematoxylin and eosin staining along with trichrome staining.

The Ehrlich/Hunt numeric scale[2] was used for the scoring of inflammatory cell infiltration, angiogenesis, fibroblast proliferation, and collagen deposition. The scores were 0 for absence, 1 for occasional presence, 2 for light scattering, 3 for abundance, and 4 for confluence of cells or fibers. Epithelial regeneration was scored according to Loewen's study.[3] The scores were 0 for no epithelium, 1 for single layer epithelium, and 2 for multilayer epithelium with complete closure for airway healing.

The statistical analysis for group comparison was made with the Mann-Whitney U-test, and the value of p<0.05 was considered as significant.

The current study was reviewed and approved by Ethics Committee for Animal Studies at Düzce University, Düzce-Turkey. All animals received humane care in compliance with the Guide for the Care and Use of Laboratory Animals.[4]

Results

None of the rats died during the surgical procedure or postoperative care. One rat had a simple skin infection which did not extend deep to the trachea. Other rats did not have any complications.

The macroscopic examination after excision of operated tracheas did not reveal any dehiscence of the suture line or obstruction of the lumen in the operated part.

The rat specimens were histologically evaluated and scored for inflammatory cell infiltration, angiogenesis, fibroblast proliferation, collagen deposition, and epithelial regeneration. Two rats from the tenoxicam group were excluded from the study during histopathological examination because of technical reasons. The scores are presented in table 1.

Table 1: Histological scoring of the cases

We found meaningful differences in fibroblast proliferation (p=0.036; <0.05) and epithelial regeneration (p=0.002; <0.05). Hence, epithelial regeneration was higher, and fibroblast proliferation was lower in the tenoxicam group (Figure 1, 2). However, the differences in inflammation, angiogenesis, and collagen deposition did not reach statistical significance.

Figure 1: Photomicrograph of histopathology from tenoxicam group displaying less fibroblast proliferation and good epithelial regeneration (H-E x 200).

Figure 2: Photomicrograph of histopathology from control group displaying distinctive fibroblastic proliferation and impaired epithelial regeneration (H-E x 200).