Comparison of intubating conditions and hemodynamic responses to tracheal intubation with different effect-site concentrations of remifentanil without muscle relaxants during target-controlled infusion of propofol.

BACKGROUND

We compared the effects of different remifentanil effect-site concentrations on intubating conditions, and cardiovascular and bispectral index score (BIS) responses to intubation at a fixed effect-site concentration of propofol without muscle relaxants.

METHODS

Sixty-four patients were randomly assigned to one of three groups: remifentanil 2 (group R2, n = 22), 4 (group R4, n = 21), or 6 ng/ml (group R6, n = 21). Anesthesia was induced using target-controlled infusion of propofol 5 microgram/ml and each concentration of remifentanil. Laryngoscopy and intubation was attempted at 2.5 min following induction. Intubating conditions were assessed as excellent, good or poor using a standard scoring system. Mean arterial pressure (MAP), heart rate (HR), and BIS values were assessed.

RESULTS

Excellent or good intubating conditions were obtained in 91% of group R4 and 95% of R6, both of which are higher compared with 32% of R2 (P < 0.01). MAP and HR decreased significantly after induction in all groups. After intubation, they recovered to baseline value in group R2 and R4 but were significantly less than baseline values in R6. BIS response to intubation was attenuated in group R4 and R6 but not R2. Hypotension was more frequent in group R6 than R2.

CONCLUSIONS

Remifentanil target concentrations of 4 or 6 ng/ml combined with 5 microgram/ml propofol provided good or excellent conditions for tracheal intubation and prevented cardiovascular and BIS response during induction without muscle relaxants. However, the use of 6 ng/ml dose was associated with frequent occurrence of hypotension and bradycardia requiring treatment.