Effect of oxygen-producing suture material on hypoxic colonic anastomoses in an experimental model

Abstract

Background: Anastomotic leak remains a significant cause of morbidity and mortality after colorectal surgery. Among multiple risk factors considered, hypoxia-ischaemia is considered to be a primary cause of intestinal anastomotic leakage. The aim of this experimental study was to assess safety, usability for surgical tasks, and efficacy of a newly developed oxygen-producing suture material in the healing of colonic anastomoses under critical conditions.

Methods: An oxygen-producing suture material was produced that is capable of releasing oxygen directly into the surrounding tissue. Off-the-shelf sutures loaded with calcium peroxide nano-crystals and covered with poly(d,l-lactide-co-glycolide) were assessed in vitro and in a rat model of hypoxic colonic anastomosis.

Results: In vitro assessment showed that these sutures can increase oxygen levels in a hypoxic environment. Potential oxygen byproducts did not seem to have a negative impact on the viability of intestinal cells. The use of oxygen-producing sutures in vivo resulted in increased tissue oxygen saturation, measured by visible light spectroscopy, and increased mechanical stability of the anastomosis.

Conclusion: Oxygen-producing suture material increased tissue oxygen saturation and mechanical stability of colonic anastomosis in a rat model.

Figure 1

Operation site The bluish aspect of the bowel serosa indicates the surgically induced tissue hypoxia. The nourishing vessels are divided and ligated (arrows), and the respective bowel segment is denuded completely from its vascular supply over a distance of 30 mm on each side of the presumed anastomosis. The anastomosis was done in an interrupted fashion using the assigned suture material per group (circle). Insert: Tissue oxygen saturation was measured non‐invasively using a handheld probe placed at each side of the (presumed) anastomosis.

Figure 2

Generation of oxygen a Shortly after putting the manufactured suture containing calcium peroxide (CPO) nano‐crystals into normal tap water, gas bubbles start to emerge from the suture. b No gas bubbles emanate from the untreated control suture. c Oxygen release was measured using a water displacement method. Some 2 mg poly(d,l‐lactide‐co‐glycolide) (PLGA)–CPO‐coated suture was added to a syringe and measured over a 72‐h period. Values are mean(s.d.).

Figure 3

Increased tissue oxygen saturation in sutured anastomoses under critical hypoxia Ineffective induction of hypoxia (low hypoxia) resulted in little effect on perianastomotic tissue oxygen saturation (Sto ₂) in anastomoses sutured with poly(d,l‐lactide‐co‐glycolide) (PLGA)–calcium peroxide (CPO), Vicryl™ or PLGA at all assessed time points. Under critical hypoxia, perianastomotic Sto ₂ was significantly higher in anastomoses performed using oxygen‐releasing sutures compared with controls (Vicryl™ or PLGA) at all measured time points. Oxygen‐producing sutures were able to maintain Sto ₂ close to the baseline level (dashed line). Values are mean(s.d.). Baseline, n = 69; low hypoxia, n = 33; critical hypoxia, n = 36; PLGA–CPO, Vicryl™ and PLGA, n = 4 each, per postoperative day. *P ≤ 0·001, †P < 0·050 (one‐way ANOVA and Student's t‐test contrasts).

Figure 4

Colonic crypt depth a Histological examination demonstrated significantly more perianastomotic mucosal growth when using oxygen‐releasing compared with Vicryl™ sutures at all assessed postoperative time points. b Bar graph shows that there was no significant difference in mucosal thickness between poly(d,l‐lactide‐co‐glycolide) (PLGA)–calcium peroxide (CPO) and PLGA, or between PLGA and Vicryl™ anastomoses. Values are mean(s.d.). PLGA–CPO, Vicryl™ and PLGA, n = 4 each, per postoperative day. *P < 0·050 (one‐way ANOVA and Student's t‐test contrasts).

Figure 5

Mechanical stability of anastomoses Anastomoses performed using oxygen‐releasing suture material (poly(d,l‐lactide‐co‐glycolide) (PLGA)–calcium peroxide (CPO)) sustained significantly higher intraluminal air pressure before leakage than non‐oxygen‐releasing controls (Vicryl™ and PLGA) on days 1 and 3 after surgery. Values are mean(s.d.). PLGA–CPO, Vicryl™ and PLGA, n = 4 each, per postoperative day. *P ≤ 0·010, †P < 0·050 (one‐way ANOVA and Student's t‐test contrasts).