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Interaction modeling of propofol and sufentanil on loss of consciousness
1Department of Anesthesiology, University of Ulm, Germany. stefanschraag@compuserve.com
Study Objectives:
To examine the possible pharmacodynamic interaction of propofol and sufentanil with respect to the induction of loss of consciousness.
Design:
Prospective, randomized, double-blinded study.
Setting:
University hospital.
Patients:
30 female, ASA physical status I and II patients undergoing elective gynecologic surgery.
Interventions:
Patients were allocated randomly to receive an individual combination of propofol (1, 2, 3, 4, 5, or 6 micrograms/ml) and sufentanil (0.1, 0.2, 0.3, 0.5, or 1.0 ng/ml) target blood concentrations using target-controlled infusions.
Measurements And Main Results:
Study endpoint was loss of consciousness, which was tested by response to verbal commands and classified as responder or nonresponder, as assessed by the anesthetist, who was blinded to the drugs' target blood concentrations. Nonlinear association (interaction) of both drugs was accomplished with logistic regression analysis using the maximum likelihood method, based principally on the hypothesis of interaction: In [p/(1-p)] = beta 0 + beta 1 x Cprop + beta 2 x Csuf + beta 3 x Cprop x Csuf with a p-value < 0.05 for coefficient estimates considered significant. In the logistic regression model, sufentanil and propofol showed no supra-additive interaction regarding loss of consciousness (p = 0.5916).
Conclusions:
Our results give no evidence of additional hypnotic properties of sufentanil compared to the other fentanyl congeners, although logistic regression may be of limited value in modeling interaction of hypnotic-analgesic combinations.