婦人科手術における脳組織酸素化指標と術後悪心・嘔吐との関連：前向き観察研究

Relationship between the Cerebral Tissue Oxygenation Index and Postoperative Nausea and Vomiting in Gynecologic Surgery：A Prospective Observational Study

要旨

　術後悪心・嘔吐（postoperative nausea and vomiting：PONV）の代表的なリスク評価法であるApfelスコアの予測精度は高くない。一方で脳内低酸素状態がPONVと関連する可能性がある。婦人科手術を受けた患者を対象に脳組織酸素化指標（tissue oxygenation index：TOI）とPONVとの関連を検討し，TOI測定がApfelスコアの精度を向上させるか検討した。

　従来の危険因子とは独立して “TOIの初期値” はPONVと関連した〔オッズ比 4.141［95％信頼区間（confidence interval：CI）：1.326-12.926］，P＝0.0144〕。“TOIの初期値” をApfelスコアに追加するとPONVのリスク評価精度が向上した（曲線下面積の差 0.1724［95％CI：0.0278-0.3170］，P＝0.0194）。

　TOIの測定がPONVの予測精度を向上させる可能性が示唆されたが，臨床上の差異は小さく，TOIを用いたPONV予測は臨床上困難といえた。

　Background：Although the Apfel score is commonly used to assess the risk of the development of postoperative nausea and vomiting（PONV）, it is not sufficiently accurate. It has been reported that PONV is associated with hypoxia of cerebral tissue.

　Methods：We investigated the relationship between a cerebral tissue oxygenation index（TOI）and the development of PONV in patients undergoing gynecologic surgery（n＝60, age 49.4±12.7）, and we sought to determine whether using this TOI improves the Apfel score’s accuracy.

　Results：The TOI at baseline（i. e., at the start of supplemental oxygen）was significantly associated with the occurrence of PONV〔odds ratio 4.141［95％ confidence interval（CI）：1.326-12.926］, P＝0.0144〕, independently of the risk factors described in previous studies. The addition of the baseline TOI to the Apfel score significantly improved the accuracy of the risk assessment of PONV（area under the curve difference：0.1724,［95％CI 0.0278-0.3170］, P＝0.0194）.

　Conclusions：These results suggest that obtaining patients’ cerebral TOI values may improve the accuracy of predicting PONV；however, the clinical difference was small and predicting PONV by using this TOI was clinically difficult.