Bispectral index during modified rapid sequence induction using thiopentone or propofol and rocuronium

This randomized controlled trial compared Bispectral Index (BIS) values in 40 patients after a modified rapid sequence induction using thiopentone 4 mg/kg or propofol 2 mg/kg with rocuronium 0.6 mg/kg as muscle relaxant. Endotracheal intubation was performed at 60 seconds from induction of anaesthesia and BIS values were recorded for three minutes after induction. At the 120, 150 and 180 second measurements there was a significantly greater proportion of subjects with BIS values < or = 60 ("anaesthetized") in the propofol group compared with the thiopentone group (P values < 0.02, < 0.01 and < 0.01 respectively). All intubations were completed within two minutes. No explicit recall of intubation was detected clinically with either induction agent. The BIS scores we have measured suggest that thiopentone 4 mg/kg is more likely to be associated with lighter planes of anaesthesia and consequent risk of awareness than propofol 2 mg/kg, if intubation is delayed or prolonged.