IS IMMUNE FUNCTION BETTER PRESERVED AFTER LAPAROSCOPIC VERSUS OPEN COLON RESECTION

The purpose of this preliminary study was to evaluate immunologic responses to laparoscopic vs standard open colon resection and to evaluate possible mediators of any differences found. Specifically, we compared cortisol levels and delayed-type hypersensitivity response after each method of colon resection in a group of 20 pigs. Two groups of 10 animals each were treated in identical fashion including bowel preparation, anesthesia, and postoperative management. The only difference between groups was that one underwent laparoscopic and the other an open colon resection. Blood specimens for cortisol were drawn before, during, and immediately postoperatively as well as at 11 A.M. on postoperative days 1 and 2. All animals had been previously immunized as piglets with Sow Bac-E (Oxford Veterinary, Worthington, MN), an antigen preparation of common pig pathogens. At the conclusion of the operative procedure 0.5 cc of the antigen was injected intradermally on the right forelimb of the animals. At 48 and 72 h postoperatively the largest diameters of induration surrounding the injection site were measured and averaged. Cortisol levels were measured in serum samples by radioimmunoassay (Met-Path, Rockville, MD). Statistical significance was determined by t-test. Results of skin antigen testing showed that the group of pigs that underwent laparoscopic resection had a 20% greater response, 1.54 cm +/- 0.28 cm at 48 h and 1.53 cm +/- 0.18 cm at 72 h. For the open-surgery group results were 1.24 cm +/- 0.26 cm at 48 h and 1.32 cm +/- 0.21 cm at 72 h, P < 0.05 for the difference between groups at both 48 and 72 h. Cortisol levels were not significantly different between groups at any of the time points. We conclude that T-cell-related immune function in this model, as measured by delayed-type hypersensitivity, is better preserved after laparoscopic than open colon resection. We further conclude that cortisol levels are not responsible for the improved preservation of the immune response. The benefits of improved postoperative immune function may be significant for patients undergoing laparoscopic colon resection.