Background: 30-67% of patients undergoing laparoscopic surgery reports shoulder pain. Besides, post-surgical course of patients undergoing converted laparoscopic procedures is similar to the course of patients who received a completely laparoscopic procedure. It is supposed that there is a temporary neurotoxic damage of the peritoneal sensitive nervous fibres defined by CO2.
Methods: A prospective review has been carried out by histologically analyzing 38 peritoneal biopsies from 10 selected patients, during different laparoscopic surgical procedures (6 cholecystectomies, 2 appendectomies, 1 selective bilateral ligature of the spermatic vessles) and at different times during each operation. Patients whom anamnesis, clinical or local conditions were suggestive for peritoneal flogosis were excluded from the study: therefore only 29 biopsies from 8 patients have been considered useful to the study.
Results: Histological analysis has been carried out with different methods of coloration (hematoxylin eosin, argentic staining) and at different magnifications (30x, 60x, 100x), without electronical microscopy or immunohistochemical studies. No biopsy showed signs of damage of the nervous structures.
Conclusions: Certainly, the realization of a pneumoperitoneum at CO2 doesn't cause damages of the peritoneal sensitive fibres. It has been demonstrated that the abdominal introduction of CO2 causes a "relative peritoneal acidosis", directly depending from the percentage of CO2 employed: the peritoneal pH decreases to 6.9 after 15 min of pneumoperitoneum with CO2 at 100% and to 7.35% with CO2 at 5% of air. Probably this condition causes a temporary biochemical change that defines reduction of the nervous impulses and, therefore, the "peritoneization" of the patient subjected to laparoscopic procedure. The "biochemical hypoesthesia", based on a change of the peritoneal homeostasis, would translate itself in a beneficial effect for the patient, persisting also when converted to laparotomic operation due the impossibility to proceed under laparoscopy, held up by the residual pneumoperitoneum.