EtCO₂ and PONV: are the results really important?

To the Editor:

We thank Fujimoto et al. for probing the correlation of intraoperative end-tidal carbon dioxide (EtCO₂) with the risk of postoperative nausea and vomiting (PONV) in patients undergoing gynecological surgery [1]. We have some comments.

First, considerable evidence illustrated that a vast array of perioperative factors contribute to the incidence of PONV. We appreciate that the authors have already balanced a battery of crucial factors. However, we argue that they may miss some important influencing ones, including type and dose of antiemetics (e.g. 5HT3 antagonists), pain, history of PONV and motion sickness (the authors have acknowledged these limitations) [2, 3]. Second, area under the curve (AUC) of the lowest EtCO₂ was only 0.61 with the best cutoff value of 32 mmHg in patients with PONV; however, it seemed that the authors did not provide detailed information on its sensitivity and specificity. Therefore, EtCO₂ might not be an ideal indicator for predicting the incidence of PONV. The conclusion of the current study could be more convincible by addressing aforementioned considerations.

In all, we thank the authors for providing us a new potential predictor of PONV though some issues still needs to be answered, as well as urging us to seek effective predicting models to identify high risk patients. Additionally, the optimal strategy with bundled care should be suggested in the prevention and treatment of PONV.