POSTOPERATIVE IMMUNE FUNCTION VARIES INVERSELY WITH THE DEGREE OF SURGICAL TRAUMA IN A MURINE MODEL

Background: Major surgery through a laparotomy incision is associated with a postoperative reduction in immune function. Studies in rats inv olving sham procedures suggest that immune function may be preserved a fter laparoscopy. This study investigates the effects of incision leng th and exposure method for bowel resection with respect to postoperati ve immune function as assessed by delayed-type hypersensitivity (DTH) reactions. Methods: Male Sprague Dawley rats (n = 175) were challenged preoperatively, immediately postoperatively, and on postoperative day 2 with an intradermal injection of 0.2 mg phytohemagglutinin (PHA), a nonspecific T-cell mitogen. The averages of two measures of perpendic ular diameters were used to calculate the area of induration. Anesthes ia control rats underwent no procedure. Minilaparotomy rats underwent a 3.5-cm midline incision. Sham full laparotomy rats underwent a 7-cm midline incision. The open bowel-resection group underwent a cecal lig ation and resection through a 7-cm midline incision. In the laparoscop ic-assisted resection group a CO2 pneumoperitoneum and four-port techn ique was utilized to deliver the cecum through a 7-mm port where the c ecum was extracorporeally ligated anti resected. Results: Preoperative responses were similar in all five groups. Incision length: Full lapa rotomy group responses were 20% smaller than anesthesia control respon ses on postoperative day (POD)1 through POD4 (p < 0.02). At no time po int were the responses in the minilaparotomy group significantly diffe rent from either anesthesia control or full laparotomy group responses . Exposure method: The laparoscopic-assisted resection group responses were 20% larger than open group responses at the time of two of the f our postoperative measurements (p < 0.05, both comparisons). At all po stoperative time points, open resection group responses were significa ntly smaller than control responses (p < 0.05, all comparisons), where as at no time point were laparoscopic group responses significantly di fferent from control responses. Conclusion: We conclude that postopera tive cell-mediated immune function varies inversely with the degree of surgical trauma. Results from the minilaparotomy and laparoscopy grou ps suggest that procedures done through small incisions may result in preservation of postoperative immune function.