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2 results

  • A comparison between bispectral index analysis and auditory-evoked potentials for monitoring the time to peak effect to calculate the plasma effect site equilibration rate constant of propofol

  • M.-Z. Zhang, Q. Yu, Y.-L. Huang, S.-J. Wang, X.-R. Wang
  • Journal:
    European Journal of Anaesthesiology / Volume 24 / Issue 10 / October 2007
    Published online by Cambridge University Press:
    01 October 2007, pp. 876-881
    Print publication:
    October 2007
  • Background and objectives

    To the best of our knowledge, the value of the plasma effect site equilibration rate constant (ke0) of propofol has not been reported in Chinese patients. The aim of this prospective, randomized study was to examine the characteristics of the time to peak effect (TPEAK) of propofol, a pharmacokinetic-independent descriptor of blood–brain equilibration, and ke0 derived from TPEAK with A-line auditory-evoked potential monitor and Aspect A-2000 bispectral index monitor in Chinese patients.

    Methods

    Two-hundred ASA I patients received a submaximal bolus dose of propofol (1.5 mg kg−1). TPEAK was randomly measured by means of the A-line auditory-evoked potential monitor (Group AAI (auditory-evoked potential index), n = 100) or the Aspect A-2000 bispectral index monitor (Group BIS, n = 100). Using TPEAK and four previously validated pharmacokinetic parameter sets of propofol, the ke0 was estimated according to a method proposed recently.

    Results

    The mean TPEAK was 145 ± 35 s (50–224 s) and 74±24 s (38–143 s) in Groups AAI and BIS, respectively (P < 0.01 between groups). There were no correlations between the patient’s age and TPEAKs (r = 0.147 and 0.031 for Groups AAI and BIS). The median ke0 in Group AAI was 0.64 min−1 with the model of Marsh, 0.17 min−1 with the Schnider model, 0.78 min−1 with the Tackley model and 0.93 min−1 with the Shafer model. The median ke0 in Group BIS was 1.87 min−1 with the model of Marsh, 0.83 min−1 with the Schnider model, 2.14 min−1 with the Tackley model and 2.48 min−1 with the Shafer model (P < 0.01 between groups and models).

    Conclusions

    The TPEAK of propofol measured by the A-line auditory-evoked potential monitor is different from that measured by the Aspect A-2000 bispectral index monitor. The TPEAKs of propofol from auditory-evoked potential index and bispectral index, and the values of ke0 calculated based on TPEAKs are different from previous reports and appear to be not affected by age. Further studies need to be taken to validate clinically the ke0 values of propofol.

  • Comparative assessment of the effects of alfentanil, esmolol or clonidine when used as adjuvants during induction of general anaesthesia

  • S. Fernandez-Galinski, S. Bermejo, R. Mansilla, O. Pol, M. M. Puig
  • Journal:
    European Journal of Anaesthesiology / Volume 21 / Issue 6 / June 2004
    Published online by Cambridge University Press:
    23 December 2004, pp. 476-482
    Print publication:
    June 2004

  • Summary

    Background and objective: This randomized, double-blinded, prospective study compared the effects of clonidine, esmolol or alfentanil on the level of hypnosis and haemodynamic responses to intravenous induction of anaesthesia and endotracheal intubation.

    Methods: Forty-five patients scheduled for elective surgery were allotted to one of three groups. They were given either alfentanil 3 μg kg−1min−1 (n = 15); esmolol 1 mg kg−1min−1 (n = 16) or clonidine 3 μg kg−1 (n = 14) as a 10 min infusion. The infusions of alfentanil and esmolol, but not of clonidine, were maintained during endotracheal intubation. Anaesthesia was induced with midazolam (2 mg) and thiopental as required to suppress the eyelash reflex. Atracurium (0.5 mg kg−1) was given to produce neuromuscular block. Mean arterial pressure, heart rate, and bispectral index were recorded on arrival (baseline), after study drug infusion, after injecting midazolam and thiopental, as well as after endotracheal intubation. ANOVA and χ2-test were used for analysis.

    Results: Blood pressure, heart rate and the bispectral index were unaltered by the study drugs, but thiopental requirements were reduced by alfentanil and clonidine (P < 0.014). Mean arterial pressure values (mean ± standard error of mean) in the alfentanil, esmolol and clonidine groups were: baseline: 107.8 ± 3.8; 106.6 ± 3.9; 103.4 ± 3.7 mmHg; after thiopental: 74.0 ± 4.2; 85.6 ± 4.3; 94.2 ± 4.1 mmHg and after endotracheal intubation: 91.7 ± 5.3; 114.1 ± 6.9; 123.6 ± 5.6 mmHg, respectively (two-way ANOVA, P < 0.001). Mean arterial pressure changed significantly after intubation from baseline (P < 0.001) after alfentanil (− 15%) and clonidine (+ 20%) but not after esmolol (+ 7%), while the changes between pre- and postintubation values were similar in all groups (24–33% increase). The bispectral index indicated that all patients had an adequate level of hypnosis, but the variability was higher in the esmolol group (P < 0.002).

    Conclusions: None of the study drugs blocked the increase in mean arterial pressure induced by endotracheal intubation, but esmolol provided better overall haemodynamic stability. All groups had an adequate level of hypnosis.