title: [Simplified method to maintain propofol blood concentration in an approximately constant level associated to nitrous oxide in pediatric patients].
abstract: OBJECTIVE
  Maintaining target-controlled propofol blood concentrations in approximately constant levels is a technique that can be used in a simple way in the operating room. The aim of this study was to compare in clinical and laboratorial terms propofol infusion in children, using Shorts and Marshs pharmacokinetic parameters.
  
  
  METHODS
  Forty-one patients of both genders, aged 4 to 12 years, physical status ASAI or ASAII were distributed in two groups: Group S (n = 20) and Group M (n = 21). Shorts pharmacokinetic parameters were applied to group S, while Marshs pharmacokinetic parameters were applied to group M. Intravenous anesthesia was induced with 30 microg.kg-1 bolus alfentanil, 3 mg.kg-1 propofol and 0.08 mg.kg-1 pancuronium. Patients were intubated and anesthesia was maintained with N2O/O2 (60%) in controlled mechanical ventilation. Propofol infusion in group S was 254 microg.kg-1 (30 min) followed by 216 microg.kg-1.min-1 for additional 30 minutes. Propofol infusion in group M was 208 microg.kg-1 (30 min.) followed by 170 microg.kg-1.min-1 for additional 30 minutes. Using specific pharmacokinetic parameters for each group, the goal was a target-concentration of 4 microg.kg-1 propofol. Three blood samples were collected (at 20, 40 and 60 minutes) to measure propofol by the High Performance Liquid Chromatography method.
  
  
  RESULTS
  Groups S and M were similar in age, height, weight and gender (p > 0.05). There were no statistically significant differences between groups in SBP, DBP, HR, FiN2O, hemoglobin SpO2 and end tidal P ET CO2. The number of repeated alfentanil boluses showed no statistically significant difference between both groups. Bispectral index (BIS) showed also no statistically significant differences between M0 (awaken) and remaining moments in both groups. Error Performance Median (EPM) and Error Performance Absolute Median (EPAM) values were statistically different between groups in moment 60. Median propofol blood concentrations (microg.kg-1) were significantly different between groups M and S in moment 60 and between moments 40 and 60 in group S.
  
  
  CONCLUSIONS
  Anesthesia with propofol using Marshs pharmacokinetic parameters (group M) showed a lower error rate for obtaining 4 microg.kg-1 propofol target-concentration. In addition, less propofol was needed to obtain similar clinical results. For these reasons, it should be the method of choice for children ASA I aged 4 to 12 years.
authors.affiliation: Departamento de Anestesiologia, Universidade Estadual de São Paulo, Brazil. ptgv@uol.com.br
authors.forename: Pedro Thadeu Galvão
authors.initials: PT
authors.lastname: Vianna
authors.forename: Elizabeth Pricoli
authors.initials: EP
authors.lastname: Vilela
authors.forename: Francisco Carlos Obata
authors.initials: FC
authors.lastname: Cordon
authors.forename: Lídia Raquel de
authors.initials: LR
authors.lastname: Carvalho