Changes of Entropy Index and Cerebral Oxygen Metabolism in the Maintenance of Remifentanil Anesthesia and Their Predictive Value for Postoperative Hyperalgesia.

Objective: To explore the changes of entropy index and cerebral oxygen metabolism in the maintenance of remifentanil anesthesia and the predictive value of postoperative hyperalgesia.
Methods: A total of 266 patients undergoing general anesthesia in our hospital from January 2020 to October 2021 were selected, and remifentanil was used to maintain anesthesia. The state entropy, reaction entropy, and cerebral oxygen metabolism indexes (cerebral oxygen uptake rate (CERO ₂ ), arterial-venous blood oxygen difference (Da-jvO ₂ )) of patients before induction of anesthesia, 15 minutes during the operation, and at the end of the operation were compared. The influencing factors of postoperative hyperalgesia were analyzed. The logistic regression model of postoperative hyperalgesia was established, and the value of entropy index and cerebral oxygen metabolism in predicting postoperative hyperalgesia was evaluated by drawing the receiver operating characteristic curve (ROC).
Results: The state entropy, response entropy, and CERO ₂ at 30 min during the operation and at the end of the operation were lower than those before the induction of anesthesia, and Da-jvO ₂ was higher than that before the induction of anesthesia ( P < 0.001). At the end of the operation, the state entropy, reaction entropy, and CERO ₂ were higher than 30 minutes during the operation, and Da-jvO ₂ was lower than 30 minutes during the operation ( P < 0.001). The dosage of remifentanil, reaction entropy, and CERO ₂ at the end of the operation entered the logistic model. The AUC value of the reaction entropy and CERO ₂ combined to predict postoperative hyperalgesia at the end of the operation was 0.851 greater than the reaction entropy at the end of the operation ( χ ² = 3.847, P = 0.036), CERO ₂ ( χ ² = 2.589, P = 0.010) single index predictive value.
Conclusion: The entropy index and cerebral oxygen metabolism in general anesthesia patients change with the progress and discontinuation of remifentanil maintenance anesthesia, and the combination of the two has a high predictive power in postoperative hyperalgesia risk assessment. When the reaction entropy > 54.23, CERO ₂ > 34.14%, or the total dosage of remifentanil ≥ 30  μ g/kg at the end of the operation, we should be highly vigilant of the occurrence of postoperative hyperalgesia and postoperative analgesia management should be strengthened.
Competing Interests: The authors declare no competing interests.
(Copyright © 2022 Tianhao Zhang and Fang Ma.)