Bispectral Index Guided Timing of Intubation without Neuromuscular Blockade during Sevoflurane Induction of Anaesthesia in Adults

Abstract

The aim of this study was to assess the effectiveness of bispectral index monitoring (BIS) as a guide to the timing of intubation during sevoflurane induction of anaesthesia without the use of neuromuscular blocking agents in adults, and specifically, whether a target BIS value of 25 provides better intubating conditions than a target BIS of 40. Forty patients were randomized into one of two groups, a target BIS 25 (n=21) or a target BIS 40 (n =19). Patients received premedication with midazolam 20 μg/kg and fentanyl 0.5 μg/kg. Sevoflurane induction of anaesthesia was initiated and titrated to reach the target BIS value and maintained within the target range for two minutes. The trachea was then intubated, with intubating conditions being assessed using a standardized scale. The BIS 25 group had a superior median intubating score of 4 (range 3–9, [IQR 4–5]) vs the BIS 40 group with a median of 7 (5–10, [6–9], P<0.001). The time to reach target BIS values was not statistically different (BIS 25 group 6.6 min, BIS 40 group 5.1 min, P=0.054). End-tidal sevoflurane concentration upon reaching the target BIS was higher in the BIS 25 group (5.3%±1.2%) vs the BIS 40 group (3.5% ±0.95) (P<0.001). There was no statistical difference in haemodynamic parameters between groups. A target BIS value of 25 provides good to excellent intubating conditions and better intubating conditions than a target BIS of 40 during sevoflurane induction of anaesthesia without the use of neuromuscular blocking agents.