Estimation of the plasma effect site equilibration rate constant of sufentanil in children using the time to peak effect of heart rate and blood pressure

Objectives: Although targeting the effect site concentration may offer advantages over the traditional forms of administering intravenous anesthetics, it is not applicable for sufentanil in children because its plasma effect site equilibration rate constant (k _e0) is not known yet. We estimated k _e0 of sufentanil in children using the time to peak effect (t_peak) method. Materials and Methods: Under general anesthesia, sufentanil t_peak was measured after administration of a submaximal bolus dose by means of the decrease in heart rate, blood pressure and calculated approximate entropy (ApEn) of electroencephalogram in 105 children (age range: 3-11 years). k _e0 was estimated using t_peak and known sufentanil pharmacokinetic parameters in normal children. Results: The mean t_peaks were measured as 44 ± 22 s and 227 ± 91 s by heart rate and by mean blood pressure respectively. The estimated k _e0 were 5.16/min and 0.49/min by heart rate and blood pressure respectively. t_peak could not be measured using the ApEn, thus k _e0 could not be calculated by ApEn in children. Conclusions: Shorter measured sufentanil t_peak by heart rate compared to blood pressure indicate that the heart rate decrease faster than decreasing of blood pressure. Moreover, the calculated sufentanil k _e0 in children depends on the pharmacodynamics parameters.