title: Effects of cardiopulmonary bypass on propofol pharmacokinetics and bispectral index during coronary surgery.
abstract: OBJECTIVE
  Cardiopulmonary bypass is known to alter propofol pharmacokinetics in patients undergoing cardiac surgery. However, few studies have evaluated the impact of these alterations on postoperative pharmacodynamics. This study was designed to test the hypothesis that changes in propofol pharmacokinetics increase hypnotic effects after cardiopulmonary bypass.
  
  
  METHODS
  Twenty patients scheduled for on-pump coronary artery bypass graft (group, n=10) or off-pump coronary artery bypass graft (group, n=10) coronary artery bypass grafts were anesthetized with sufentanil and a propofol target controlled infusion (2.0 microg/mL). Depth of hypnosis was monitored using the bispectral index. Blood samples were collected from the induction of anesthesia up to 12 hours after the end of propofol infusion, at predetermined intervals. Plasma propofol concentrations were measured using high-performance liquid chromatography, followed by a non-compartmental propofol pharmacokinetic analysis. Data were analyzed using ANOVA, considering p<0.05 as significant.
  
  
  RESULTS
  After cardiopulmonary bypass, despite similar plasma propofol concentrations in both groups, bispectral index values were lower in the on-pump coronary artery bypass graft group. Time to extubation after the end of propofol infusion was greater in the on-pump coronary artery bypass graft group (334 +/- 117 vs. 216 +/- 85 min, p = 0.04). Patients undergoing cardiopulmonary bypass had shorter biological (1.82 +/- 0.5 vs. 3.67 +/- 1.15 h, p < 0.01) and terminal elimination (6.27 +/- 1.29 vs. 10.5h +/- 2.18, p < 0.01) half-life values, as well as higher total plasma clearance (28.36 +/- 11.40 vs.18.29 +/- 7.67 mL/kg/min, p = 0.03), compared to patients in the off-pump coronary artery bypass graft group.
  
  
  CONCLUSIONS
  Aside from the increased sensitivity of the brain to anesthetics after cardiopulmonary bypass, changes in propofol pharmacokinetics may contribute to its central nervous system effects.
authors.affiliation: Serviço de Anestesiologia e Terapia Intensiva Cirúrgica, Instituto do Coração, Hospital das Clínicas, Faculdade de Medicina da Universidade de São Paulo - São Paulo/SP, Brazil. navajasbarbosa@superig.com.br
authors.forename: Ricardo Antonio G
authors.initials: RA
authors.lastname: Barbosa
authors.forename: Silvia Regina C Jorge
authors.initials: SR
authors.lastname: Santos
authors.forename: Paul F
authors.initials: PF
authors.lastname: White
authors.forename: Valéria A
authors.initials: VA
authors.lastname: Pereira
authors.forename: Carlos R
authors.initials: CR
authors.lastname: Silva Filho
authors.forename: Luiz M S
authors.initials: LM
authors.lastname: Malbouisson
authors.forename: Maria José C
authors.initials: MJ
authors.lastname: Carmona