Surgical trauma does not decrease resistance to infection.

Objective: To investigate the effect on survival of two operations done at various intervals before the induction of monobacterial or multibacterial peritonitis in rats.

Design: Laboratory study.

Setting: Teaching hospital, Belgium.

Material: Inbred male white wistar R/A rats.

Interventions: Posterolateral laparotomy, hindleg amputation, or control (anaesthetic only) (n=90 animals in each group), followed by induction of Escherichia coli or Staphylococcus aureus peritonitis at 1, 7 or 14 days. Further groups of rats were similarly operated on (50 in each group), but peritonitis was induced by caecal ligation and puncture.

Main Outcome Measure: Survival 7 days after induction of peritonitis.

Results: Of the rats in which E. coli was used to induce peritonitis 27/28 (96%), 29/29 (100%), and 21/30 (70%) had survived 7 days after induction of peritonitis in the group that underwent posterolateral laparotomy, compared with 18/30 (60%), 20/28 (71%), and 18/28 (64%) in the control group; p 0.001, 0.002, and 0.78, respectively. The figures for hindleg amputation were 21/27 (78%), 23/27 (85%), and 17/30 (57%). The corresponding figures for S. aureus peritonitis were for posterolateral laparotomy 28/30 (93%), 20/30 (67%), and 24/29 (83%) compared with controls 21/30 (70%), 9/30 (30%), and 20/29 (69%); p 0.04, 0.009, and 0.75, respectively. The figures for hindleg amputation were 21/30 (70%), 12/30 (40%), and 23/30 (77%). Similar results were obtained with peritonitis induced by caecal ligation and puncture.

Conclusions: Although surgical trauma may depress various aspects of the immune response in rats, it does not decrease their resistance to intraperitoneal microbial infections. The previous opening of the peritoneal cavity seemed to improve survival in our model.