Bladder pressure monitoring and CO2 gas-related adverse events during per-oral endoscopic myotomy

Per-oral endoscopic myotomy (POEM) is a minimally invasive treatment for esophageal achalasia. However, POEM has the potential risk of inducing carbon dioxide (CO2) gas-related adverse events, such as pneumoperitoneum, pneumomediastinum, and pneumothorax. The aim of this study was to evaluate the usability of bladder pressure monitoring as an index of CO2 gas-related pneumoperitoneum. The monitoring of bladder pressure and lung compliance and the incidence of iatrogenic pneumoperitoneum were retrospectively studied in 20 patients who underwent POEM between June 2013 and March 2015. The bladder pressure was measured using a Foley catheter. Abdominal distention was found in nine patients. The bladder pressure was significantly higher in the nine patients with the distention findings compared with patients without distention [7 (6-9)mmHg vs. 1 (0-2)mmHg; P<0.05]; however, the decrease in dynamic lung compliance was not significantly different compared with patients without distention [-7 (-9.3 to -5.1) vs. -5 (-10.2 to -1.3)ml/cmH(2)O; P=0.62]. Based on postoperative changes on CT scans; the following were the observations: pneumomediastinum (55%), minor pneumothorax (5%), pleural effusion (45%), atelectasis (15%), pneumoperitoneum (85%), and subcutaneous emphysema (15%). No significant clinical status was found among the patients postoperatively. Bladder pressure monitoring might be useful for detecting pneumoperitoneum during POEM.