Summary

Background and objective: The electroencephalographic Narcotrend Index (NI) is a measure of the hypnotic component of general anaesthesia. The purpose of this study was to evaluate the impact of Narcotrend guidance on propofol consumption and emergence times in children receiving total intravenous anaesthesia with propofol and remifentanil. Methods: Thirty children, aged 1–11 yr, scheduled for paediatric urological surgery were enrolled. Remifentanil was given to all patients at a constant infusion rate of 0.3 μg kg−1 min−1 throughout anaesthesia. Patients were randomly allocated to receive a continuous propofol infusion adjusted either according to a conventional clinical practice (Group C: n = 15) or guided by Narcotrend monitoring (Group NI: n = 15; target NI 60 ± 5). All patients were connected to the Narcotrend Monitor, but in Group C the anaesthetist was blinded to the screen of the monitor. Propofol consumption (mg kg−1 h−1) and emergence times (min) were the primary and secondary outcome measures. Results: Propofol consumption (median [inter-quartile range]) was significantly lower in Group NI compared to Group C (NI: 7.0 [6.4–8.2] vs. C: 9.3 [8.3–11.0] mg kg−1 h−1; P < 0.001), whereas Log-Rank-analysis revealed no intergroup difference in emergence times (Group NI: mean [95% confidence interval (CI)] 12.8 [11.2–14.4] min; Group C: 16.4 [12.6–20.2] min; P = 0.10). Haemodynamic variables remained stable within age-related limits, and there were no observations of adverse events, especially no clinical signs of intraoperative awareness in any patient. Conclusion: Narcotrend monitoring for guidance of propofol/remifentanil anaesthesia in children results in reduced propofol consumption compared to a conventional clinical practice.

Summary

Background and objective: Many anaesthesiologists still interpret haemodynamic responses as signs of insufficient cortical suppression. The aim was to illustrate how haemodynamics may only poorly reflect the level of cortical suppression and that electroencephalographic monitoring could indicate different relationships between cortical effects and haemodynamics.

Methods: Anaesthesia was induced with thiopental (7 mg kg−1), and fentanyl (2 μg kg−1) with succinylcholine (1.5 mg kg−1) for neuromuscular blockade in the 11 patients of Group 1. In Group 2 (n = 15), thiopental (7 mg kg−1) and succinylcholine (1.5 mg kg−1) were given. In Group 3, the patients (n = 13) received thiopental (7 mg kg−1), fentanyl (2 μg kg−1) and cisatracurium (0.1 mg kg−1), and they were intubated 3 min later than the patients in Groups 1 and 2. We determined conventional electroencephalographic (EEG) variables and classified 14 EEG stages in real-time ranging from A (=1), indicating full wakefulness, to F1 (=14), at profound cortical suppression.

Results: All groups had profound cortical suppression 45 s after thiopental administration, which rapidly decreased (EEG stage, 11 (6–13) versus 7 (2–13) at 4 min, P < 0.0001). Decreasing EEG stages were associated with increasing SEF 95, relative α and β power and decreasing relative δ power. During tracheal intubation, profound cortical suppression remained unchanged in Groups 1 and 2. In Group 3, cortical suppression had decreased before laryngoscopy (P < 0.005). In Group 2, 11 patients had heart rate responses to tracheal intubation, whereas only two responded in Group 1 (P = 0.015) and three in Group 3 (P = 0.02). Thirteen patients in Group 2 had arterial pressure responses, and five in Group 1 (P = 0.038). Circulatory responses did not differ between Groups 1 and 3.

Conclusions: Electroencephalographic monitoring was suitable to indicate in real-time that haemodynamics only poorly reflect rapidly changing levels of cortical suppression, and how haemodynamics and cortical activity depend on the applied combination of hypnotic and analgesic drugs during anaesthesia induction with thiopental.