A canine model to assess the biochemical stress response to laparoscopic and open surgery

Abstract

Purpose: To develop an animal model to assess the stress response to open and laparoscopic surgery. Such a model would allow objective physiologic assessment of the putative benefits of laparoscopy and provide a framework in which to compare modifications in operative and anesthetic technique that might decrease the stress of surgery.

Materials and methods: Mongrel dogs underwent laparoscopic (N = 12) or open surgical (N = 12) left nephrectomy. In 11 control animals, after induction of anesthesia and line placement, the animal underwent either no intervention (open surgery sham; N = 6) or pneumoperitoneum only (laparoscopic sham; N = 5). Serum glucose and cortisol were measured preoperatively, at skin closure, and at 4, 8, and 24 hours postoperatively. Values at each time point were compared in the laparoscopic and open surgical nephrectomy groups and in each of the two nephrectomy groups and their respective shams.

Results: Compared with baseline, there was a sharp rise in serum cortisol at the time of skin closure, with a gradual decline to baseline values by 24 hours, in all experimental animals. Significantly lower serum cortisol concentrations were seen at 4 and 8 hours postoperatively in the laparoscopic group than in the open surgery group. Cortisol was significantly higher in the open group than in the sham-open group at all time points, whereas cortisol was greater in the laparoscopic group than in the pneumoperitoneum-only group only at the 4-hour time point. No differences were seen in serum glucose between groups.

Conclusions: The serum cortisol concentration appears to be a good measure of surgical stress in the canine model. The rapid decline in serum cortisol after laparoscopy compared with open surgery may indicate a lesser degree, or quicker resolution, of surgical stress in the former. Furthermore, the similarity in cortisol curves between laparoscopy and pneumoperitoneum only suggests that surgical stress in laparoscopic surgery may be attributable mainly to the effects of pneumoperitoneum.