Wound tensile strength and contraction rate are not affected by laparotomy or pneumoperitoneum

Background: Many cellular elements responsible for wound healing are affected by laparotomy. The aim of this study was to evaluate the effects of laparotomy and CO₂ pneumoperitoneum on wound healing. Methods: Male Sprague Dawley rats were randomly assigned to one of three experimental groups. Anesthesia control rats underwent no procedure. Pneumoperitoneum group rats were insufflated with CO₂ gas. Laparotomy group rats underwent a 7-cm midline laparotomy incision. The interventions were 30 min long. For the incisional study (n= 30), a 4-cm dorsal full-thickness skin incision was made on each rat and then closed with staples. On postoperative days 7 and 14, an equal number of rats were sacrificed from each group, and wound tensile strength measurements were performed. For the excisional study (n= 45), each group of 15 rats underwent a 2-cm diameter circular dorsal full-thickness skin excision. Blinded measurements of wound area were performed every other day until wounds closed. Results: Wound tensile strength values were not significantly different among experimental groups at either time point. The study had a power of 80% to find a 30% difference at POD 7 and a power of 80% to find a 23% difference at POD 14 to a confidence level of p < 0.05. Wound contraction data from the excisional model were analyzed with the Generalized Estimation Equations statistical approach. When we modeled the treatment group as a covariate, no statistical difference was found between groups, demonstrating equal slopes across time. Conclusions: From the results of these studies, we conclude that wound healing in this model is not significantly diminished following laparotomy or peritoneal insufflation, as compared to anesthesia control. Received: 26 September 1997/Accepted: 27 January 1998