[Is entropy a monitor for the guidance of intraoperative analgesia?]

Abstract

Objective: Comparison between BIS (Bispectral Index) and state (SE) and response (RE) entropy during laparotomy for inflammatory bowel disease patients (IBD) and evaluation of the variations of RE and SE during nociceptive stimulation.

Study design: Prospective, observational study.

Patients and methods: Fourteen IBD's patients undergoing laparotomy were included. Anaesthesia aimed to maintain BIS between 40 and 60 by isoflurane and nitrous oxide. Analgesia was performed by sufentanil bolus administrated according to an increase of 20% of systolic blood pressure (SBP) and heart rate compared with the baseline values. BIS, RE and SE were measured at each nociceptive stimulation. A variance analysis (Anova) was used to assess BIS, RE and SE variations throughout surgery (p<0.05 as significant). Relationship between BIS, RE and SE was assessed by Pearson correlation (p<0.01 as significant). The ability for SE and RE to predict depth of anaesthesia and intraoperative analgesia was performed by calculating area under the receiver operated curves (AUC).

Results: BIS and entropy parameters had strictly the same evolution during anaesthesia. SBP increased significantly during nociceptive stimulation while no variation of RE was observed. A significant correlation was shown between BIS, RE and SE. The evaluation of anaesthesia depth was good for RE (AUC: 0.932+/-0.26) and SE (AUC: 0.926+/-0.27). There was however no difference between RE and SE to predict analgesic requirement.

Conclusion: Because RE includes muscular frequency analysis, it does not allow analgesic requirement evaluation in paralyzed patients.