The effect of preoperative corticosteroids on peritoneal macrophage function after laparoscopic and open abdominal surgery in a rat model.

BACKGROUND

Peritoneal macrophages play an important role in the immune response after abdominal operations. The stress response after these operations has been associated with impaired phagocytosis by peritoneal macrophages. This study examined the influence of minimally invasive techniques and preoperative corticosteroid administration on postoperative peritoneal macrophage phagocytic activity.

METHODS

After IACUC approval, 66 Sprague Dawley rats were randomly divided into 7 groups: baseline animals (B), anesthesia controls (AC), open cecectomy (OC), and laparoscopic cecectomy (LC). Within the AC, OC, and LC groups, half received intraperitoneal (IP) dexamethasone (10 mg/kg) 1 hour before surgery (+S), and the other half received an equal volume of normal saline IP (-S). Animals were observed postoperatively for 24 hours and were then euthanized. Peritoneal macrophages were harvested via intraperitoneal lavage. A phagocytosis assay was performed to calculate the net phagocytosis and percent response to the effector agent. Statistical analysis was performed using analysis of variance and a Student t test between groups. A P value of <.05 was considered significant.

RESULTS

Significant differences were observed between groups. The B group had a response rate of 94.2% +/- 56.7%, which was not different from the AC groups (-S, P = .28; +S, P = .16) or the LC-S group (P = .9). The lowest phagocytic activity rate was in the OC-S group with a response rate of 33.8% +/- 28.5%. The highest phagocytic response rates occurred in the AC +S (145.2% +/- 60.2%) and LC +S (198.1% +/- 103.5%). These were not significantly different from each other (P = .3). The LC +S group had a significantly higher percent response than all of the other groups. The phagocytic response rate of the OC +S group was not different from either the AC-S group (P = .07) or the LC-S group (P = .8); however, it was less than the AC +S group (P = .02) and the LC +S group (P = .003).

CONCLUSION

Open cecectomy resulted in greater impairment of the phagocytic activity of peritoneal macrophages than laparoscopic cecectomy. The addition of preoperative corticosteroids improved phagocytic activity back to baseline function. The combination of minimally invasive surgical technique and preoperative corticosteroid administration resulted in the greatest postoperative phagocytic function of peritoneal macrophages in a rat model.