Performance of plasma vs. effect-site TCI for propofol in elderly patients

Wagner F¹, Petscher M¹ and Schraag S²

¹ Department of Anaesthesiology, University of Ulm Medical School, Germany

² Department of Perioperative Medicine, Golden Jubilee National Hospital, Clydebank, Scotland

Background and Goal of Study

There is a debate whether propofol TCI in effect-site control is clinically superior to plasma control. We compared the clinical performance of plasma and effect-site TCI with propofol in elderly patients.

Materials and Methods

After IRB approval and informed consent 30 patients >70 years of age were randomized to receive propofol TCI in either plasma (Marsh model, 15 pts., group P) or effect-site (Schnider model, 15 pts., group E) control. Anaesthesia induction was ramped up stepwise until both BIS was <60 for at least 60 sec and patients clinically lost consciousness (LOC), starting for both groups with a target concentration of 2μg/ml, increasing to 3μg/ml and 4μg/ml, respectively, allowing a 10 min equilibration for each step. Arterial propofol blood concentrations, BIS and sedation score (OAAS) were measured throughout the experiment. Time to LOC and measured blood concentration at the hypnotic endpoints were compared.

Results and Discussions

The following tables summarises the results (mean values ± SD).

We found no difference in propofol Cm at LOC between plasma and effect-site control, whereas the time to reach this endpoint was significantly longer in effect-site control, when titrated slowly. This may have been influenced by the choice of model. The difference in performance between the two models becomes negligible after the first 20 minutes. Neither model predicted the initial filling phase correctly.

Conclusion(s)

With the exception of the initial filling phase, where the Schnider model overpredicts and the Marsh model underpredicts, propofol TCI in effect-site control (Schnider model) performs similar to plasma control (Marsh model) in elderly patients.

References

Marsh B et al. Br J Anaesth 1991;67:41-8.

Schnider T et al. Anesthesiology 1999;90:1502-16.