Hemodynamic and tissue blood flow responses to long-term pneumoperitoneum and hypercapnia in the pig.

BACKGROUND: Increased peritoneal blood flow may influence the ability of cancer cells to adhere to and survive on the peritoneal surface during and after laparoscopic cancer surgery. Carbon dioxide (CO2) pneumoperitoneum is associated with a marked blood flow increase in the peritoneum. However, it is not clear whether the vasodilatory effect in the peritoneum is related to a local or systemic effect of CO2. METHODS: In this study, 21 pigs were exposed to pneumoperitoneum produced with either CO2 (n = 7) or helium (He) (n = 7) insufflation at 10 mmHg for 4 h, or to two consecutive levels of hypercapnia (7 and 11 kPa) (n = 7) produced by the addition of CO2 to the inhalational gas mixture. Tissue blood flow measurements were performed using the colored microsphere technique. RESULTS: Blood flow in peritoneal tissue increased during CO2, but not He, pneumoperitoneum, whereas it did not change at any level of hypercapnia alone. There was no change in blood flow in most organs at the partial pressure of CO2 (PaCO2) level of 7 kPa. However, at a PaCO2 of 11 kPa, blood flow was increased in the central nervous system, myocardium, and some gastrointestinal organs. The blood flow decreased markedly in all striated muscular tissues during both levels of hypercapnia. CONCLUSION: The effect of CO2 on peritoneal blood flow during laparoscopic surgery is a local effect, and not attributable to central hemodynamic effects of CO2 pneumoperitoneum or high systemic levels of CO2.

Hypergastrinaemia induced by partial corpectomy results in development of enterochromaffin-like cell carcinoma in male Japanese cotton rats.

BACKGROUND: Among inbred female cotton rats (Sigmodon hispidus) 25%-50% of the animals develop spontaneous gastric carcinomas, whereas males have an incidence of less than 1%. The carcinomas are enterochromaffin-like (ECL)-cell derived. Animals with gastric carcinomas also have hypergastrinaemia and gastric hypoacidity, but the mechanism behind the hypoacidity is unknown. Carcinomas have been found in all female cotton rats with spontaneous hypergastrinaemia lasting more than 4 months, and a gastrin receptor antagonist prevents the development of carcinoma. The purpose of the present study was to investigate whether induced hypergastrinaemia in male cotton rats would also result in carcinomas. METHODS: Hypergastrinaemia was induced by partial corpectomy of male cotton rats, aiming at removal of 80%-90% of the corpus. A control group was sham-operated. RESULTS: All partially corpectomized animals developed persistent hypergastrinaemia. Six months after the operation, 9 out of 13 partially corpectomized animals developed gastric cancer. In the dysplastic mucosa surrounding the tumours there was an increase in chromogranin A immunoreactive cells, where numerous cells also were stained using the Sevier-Munger technique. Tumour tissue also contained cells that were chromogranin A positive and stained by Sevier-Munger. CONCLUSIONS: ECL-cell carcinomas can be induced in male cotton rats by partial corpectomy. This supports a previous statement that spontaneous carcinomas in female cotton rats are caused by gastric hypoacidity and hypergastrinaemia. In hypergastrinaemic animals, ECL-cell carcinomas develop independently of gender within a relatively short period of time, and cotton rats therefore represent an interesting model for studying gastric carcinogenesis.