Natural orifice transluminal endoscopic surgery: Cardiopulmonary safety of transesophageal mediastinoscopy

Background and study aims: Physiological reactions during natural orifice transluminal endoscopic surgery (NOTES) mediastinoscopy may lead to cardiorespiratory depression. The aim of the current study was to assess cardiopulmonary changes during transesophageal mediastinoscopy in an acute porcine model. Methods: Transesophageal mediastinoscopy was performed under general anesthesia in eight female pigs with a bodyweight of 396kg. Mediastinal access was achieved via a submucosal tunnel. The cardiac index and global end-diastolic volume index (reflecting preload) were measured every 3 minutes by transpulmonary thermodilution. The following parameters were also recorded: mediastinal pressure, heart rate, mean arterial pressure, systemic vascular resistance index (SVRI; reflecting afterload), peak inspiratory pressure, pH, pCO², and pO². Results: In three animals, small tears in the parietal pleura resulted in tension pneumothoraces. The associated cardioplumonary deterioration was fatal in one pig. The other two pigs recovered after decompression with a chest tube. In the remaining five animals there were only mild hemodynamic and respiratory changes during mediastinoscopy. There was a significant (P=0.005) but minor transient fall in cardiac index, which correlated with a small rise in SVRI (r=0.857, P<0.001). In the pigs with uncomplicated mediastinoscopy, on-demand insufflation via the endoscope resulted in median mediastinal pressures of 4.5mmHg (range 2.310.2mmHg). Overall, mediastinal and thoracic structures could be identified without difficulty via the transesophageal approach. Conclusions: NOTES mediastinoscopy carries a substantial risk of inadvertent development of a pneumothorax. Otherwise, it leads to negligible hemodynamic and pulmonary changes. In conclusion, close monitoring for the presence of a pneumothorax during NOTES mediastinoscopy appears to be mandatory.