BACKGROUND: Target controlled infusion (TCI) for propofol allows anesthesiologists to target constant blood concentrations of propofol. However, the pharmacokinetic parameters in TCI system do not take account of the patient's age, make up and gender. We evaluated the relationship between body fat percentage and the estimated effect site propofol concentrations at awakening. METHODS: Anesthesia was induced in 37 patients with fentanyl and propofol by TCI. Patients's percentage of fat was evaluated by measuring the thickness of the three parts of the skin fat with Skyndex (Caldwell Justiss, USA). After surgery and discontinuation of anesthesia, the estimated effect site propofol concentrations (EPEC) were determined when the patient could respond to verbal command. RESULTS: The EPECs at awakening were 1.5 +/- 0.2 micrograms.ml-1 in male and 1.5 +/- 0.3 micrograms.ml-1 in female. In male, the percentage of fat and body mass index (BMI) correlated significantly with EPEC (r = 0.79 and 0.49 respectively). In female, the percentage of fat and BMI did not correlate with EPEC. The estimated fentanyl effect site concentrations at awakening did not correlate with the EPEC. CONCLUSIONS: Male patients who have high percentage of fat have a tendency to delayed of awakening from propofol anesthesia. In female, however, no correlation was seen between percentage of fat and awakening time from propofol anesthesia. Measuring the percentage of fat might bring a new insight into pharmacokinetics of propofol.
BACKGROUND: Target controlled infusion (TCI) for propofol allows anesthesiologists to target constant blood concentrations of propofol. However, the pharmacokinetic parameters in TCI system do not take account of the patient's age, make up and gender. We evaluated the relationship between body fat percentage and the estimated effect site propofol concentrations at awakening. METHODS: Anesthesia was induced in 37 patients with fentanyl and propofol by TCI. Patients's percentage of fat was evaluated by measuring the thickness of the three parts of the skin fat with Skyndex (Caldwell Justiss, USA). After surgery and discontinuation of anesthesia, the estimated effect site propofol concentrations (EPEC) were determined when the patient could respond to verbal command. RESULTS: The EPECs at awakening were 1.5 +/- 0.2 micrograms.ml-1 in male and 1.5 +/- 0.3 micrograms.ml-1 in female. In male, the percentage of fat and body mass index (BMI) correlated significantly with EPEC (r = 0.79 and 0.49 respectively). In female, the percentage of fat and BMI did not correlate with EPEC. The estimated fentanyl effect site concentrations at awakening did not correlate with the EPEC. CONCLUSIONS: Male patients who have high percentage of fat have a tendency to delayed of awakening from propofol anesthesia. In female, however, no correlation was seen between percentage of fat and awakening time from propofol anesthesia. Measuring the percentage of fat might bring a new insight into pharmacokinetics of propofol.