Background: Abnormal release of inflammatory mediators following surgical injury is associated with immunological alteration, which may predispose to sepsis. Laparoscopic surgery is associated with reduced postoperative complications, but mechanisms are unclear. We hypothesized that early recovery following laparoscopic surgery may relate to minimal impairment of immune function. Design: Analysis of the temporal immune responses in two similar groups of patients randomized to open (n=22) vs laparoscopic (n=22) cholecystectomy. Patients were matched for age, height, weight, and operation time. Immune parameters, including monocyte superoxide anion (O-2(-)) and tumor necrosis factor release, neutrophil O-2(-) levels and chemotaxis, total white blood cell counts, partial arterial oxygen pressure, and serum cortisol and C-reactive protein levels were assessed preoperatively and on postoperative days 1 and 3. Results: There were significant increases (P<.001) in monocyte release of O-2(-) and tumor necrosis factor, neutrophil release of O-2(-) and chemotaxis, and white blood cell count in the open vs laparoscopic cholecystectomy study groups, with a concommitant decrease in partial arterial oxygen pressure. These findings correlated with significantly higher postoperative septic complications in the open cholecystectomy group (P<.05). There were no significant differences in either plasma cortisol or C-reactive protein levels between groups. All measurements were carried out in a blinded fashion. Conclusions: This study demonstrates that laparoscopic surgery appears to be associated with similar metabolic responses compared with open surgery, while immune parameters vary greatly between groups. The beneficial effects of laparoscopic surgery may relate, in part, to preservation of immune function in the postoperative period.Background: Abnormal release of inflammatory mediators following surgical injury is associated with immunological alteration, which may predispose to sepsis. Laparoscopic surgery is associated with reduced postoperative complications, but mechanisms are unclear. We hypothesized that early recovery following laparoscopic surgery may relate to minimal impairment of immune function. Design: Analysis of the temporal immune responses in two similar groups of patients randomized to open (n=22) vs laparoscopic (n=22) cholecystectomy. Patients were matched for age, height, weight, and operation time. Immune parameters, including monocyte superoxide anion (O-2(-)) and tumor necrosis factor release, neutrophil O-2(-) levels and chemotaxis, total white blood cell counts, partial arterial oxygen pressure, and serum cortisol and C-reactive protein levels were assessed preoperatively and on postoperative days 1 and 3. Results: There were significant increases (P<.001) in monocyte release of O-2(-) and tumor necrosis factor, neutrophil release of O-2(-) and chemotaxis, and white blood cell count in the open vs laparoscopic cholecystectomy study groups, with a concommitant decrease in partial arterial oxygen pressure. These findings correlated with significantly higher postoperative septic complications in the open cholecystectomy group (P<.05). There were no significant differences in either plasma cortisol or C-reactive protein levels between groups. All measurements were carried out in a blinded fashion. Conclusions: This study demonstrates that laparoscopic surgery appears to be associated with similar metabolic responses compared with open surgery, while immune parameters vary greatly between groups. The beneficial effects of laparoscopic surgery may relate, in part, to preservation of immune function in the postoperative period.