Analysis of pO(2) in Malignant Ascites of Patients with Peritoneal Dissemination of Gastric Cancer

OBJECTIVE: Oxygen is one of the most important environmental factors for tumor development. In this study, we examined pO(2) in malignant ascites in patients with peritoneal carcinomatosis. METHODS: In 21 patients with peritoneal dissemination of gastric cancer, ascitic fluid was collected and its pH, pCO(2) and pO(2) were determined using a blood gas analyzer. RESULTS: In 21 patients, pH of malignant ascites was significantly lower than that of arterial blood (7.39 ± 0.07, 7.44 ± 0.02, p < 0.05). Accordingly, pCO(2) tended to be higher in ascites than in arterial blood. Unexpectedly, pO(2) in malignant ascites showed relatively high values (90.4 ± 27.72 mm Hg), which were mostly the same as those of arterial blood (97.09 ± 10.33 mm Hg, p = 0.858). Even in 19 patients whose samples were collected at bedside in room air, pO(2) of malignant ascites was 85.94 ± 23.94 mm Hg, which was patently higher than that in venous blood or in solid tumor tissues. CONCLUSION: Since the oxygen level critically affects the sensitivity of tumor cells to chemotherapeutic agents through metabolic transformation, the oxygenic condition in the peritoneal cavity may be beneficial for the progression of peritoneal metastasis, and also clinically important in considering the efficacy of chemotherapy.