Estudio comparativo entre inducción rápida y lenta de propofol en infusión objetivo-controlada: concentración de propofol prevista en la región de acción. Ensayo clínico aleatorizado

Background and objective

Studies have shown that rate of propofol infusion may influence the predicted propofol concentration at the effect site (Es). The aim of this study was to evaluate the Es predicted by the Marsh pharmacokinetic model (ke0 0.26 min⁻¹) in loss of consciousness during fast or slow induction.

Method

The study included 28 patients randomly divided into 2 equal groups. In slow induction group, target-controlled infusion of propofol with plasma, Marsh pharmacokinetic model (ke0 0.26 min⁻¹) with target concentration (Tc) at 2.0 μg.mL⁻¹ were administered. When the predicted propofol concentration at the Es reached half of Es value, Es was increased to previous Es +1 μg.mL⁻¹, successively, until loss of consciousness. In rapid induction group, patients were induced with target-controlled infusion of propofol with plasma (6.0 μg.ml⁻¹) at Es, and waited until loss of consciousness.

Results

In rapid induction group, Es for loss of consciousness was significantly lower compared to slow induction group (1.67 ± 0.76 and 2.50 ± 0.56 μg.mL⁻¹, respectively, P = 0.004).

Conclusion

The predicted propofol concentration at the Es for loss of consciousness is different for rapid induction and slow induction, even with the same pharmacokinetic model of propofol and the same balance constant between plasma and effect site.