BACKGROUND: Pneumoperitoneum for laparoscopic cholecystectomy induces prompt hemodynamic changes. The rapid onset of these changes suggests a neurohumoral response. The present study investigated the effects of pneumoperitoneum on plasma catecholamines and vasopressin during laparoscopic cholecystectomy. METHODS: We studied 18 healthy patients under general anesthesia using a isoflurane and nitrous oxide (50%). In our study, nine patients were selected for Group LC; they underwent the laparoscopic cholecystectomy. The remaining nine patients constituting Group OS served as the control, and underwent minor orthopedic surgery. Venous blood samples were collected 10 minutes after the induction of anesthesia, as well as 10 minutes after the insufflation of pneumoperitoneum or skin incision, and 10 minutes after desufflation of pneumoperitoneum or skin closure. Plasma vasopressin was measured using a radioimmunoassay method. Plasma epinephrine and norepinephrine were measured using the method of high-performance liquid chromatography. RESULTS: In Group LC, the plasma concentration of vasopressin increased remarkably from 2.1 pg/ml to 70.7 pg/ml after insufflation of pneumoperitoneum, and declined to 18.3 pg/ml after desufflation (P < 0.05). Plasma concentrations of epinephrine and norepinephrine also increased significantly after insufflation of pneumoperitoneum (P < 0.05). In Group OS, however, plasma concentrations of vasopressin, epinephrine, and norepinephrine remained stable throughout the operation. CONCLUSIONS: The pneumoperitoneum resulted in a substantial increase of plasma concentrations of vasopressin as well as a signifiant increase in the plasma concentration of epinephrine and norepinephrine during laparoscopic cholecystectomy.