Reliability of Propofol Target-Controlled Infusion in Elderly Patients  

Tae Igarashi, Osamu Nagata, Hiroko Iwakiri, and Makoto Ozaki
Department of Anesthesiology, Tokyo Women’s Medical University, Tokyo, JAPAN

Background

Propofol Target-Controlled Infusion (TCI) is now commonly used for the induction and maintenance of anesthesia. The estimated plasma concentration calculated from the patient’s body weight usually correlates well with the measured plasma concentration and can thus be reliably used for normal patients. In the case of elderly patients, however, the pathophysiological characteristics might affect tissue distribution and elimination of the drugs. Accordingly, we measured the propofol plasma concentrations of elderly patients to evaluate our hypothesis that propofol TCI is still reliable for use in elderly patients.

Materials and Methods

With IRB approval, we measured plasma concentrations of propofol in ten elderly patients (70-92 yrs) undergoing elective general anesthesia. Propofol TCI was commenced at a target plasma concentration of 3 µg/ml using a TCI pump (DiprifusorTM, AstraZeneca). The target concentration was kept at 3 µg/ml for at least 2 hours. Arterial blood samples were drawn for measurement of the propofol plasma-concentration analysis at 30, 60, 90, 120 and 180 minutes after the induction of anesthesia, and at the emergence from anesthesia.

Results

The measured plasma concentrations of propofol were not significantly different from the target plasma concentrations (3 µg/ml), and they showed no tendency to increase during the 3 hours of anesthesia (Fig.1). The standard deviations (SDs) of these elderly patients, however, ranged from 0.85 to 1.09. The mean estimated and measured plasma concentrations at emergence were 0.943 +/- 0.24 µg/ml and 1.01 +/- 0.16 µg/ml , respectively.

Discussion

The measured plasma concentrations of propofol in the elderly patients showed no significant difference from the estimated values during 2-3 hours of target-controlled propofol infusion, although individual differences among the elderly patients were greater than those measured among normal patients. We concluded that propofol TCI is a reliable method for maintaining anesthesia even in elderly patients.