The effect of atropine on the bispectral index response to endotracheal intubation during propofol and remifentanil anesthesia

Atropine has been reported to increase the propofol requirements for the induction of anesthesia during continuous infusion of propofol. We investigated the influence of atropine on the bispectral index (BIS) response to endotracheal intubation during anesthetic induction with propofol and remifentanil target controlled infusion (TCI). Fifty-six patients aged 18-50 years undergoing general anesthesia, were enrolled. For induction of anesthesia, propofol TCI was set at a target effect-site concentration of 4.0 mu g/ml. Two minutes later, remifentanil was started at an effect-site concentration of 4.0 ng/ml. Four minutes after the start of propofol TCI, patients received either atropine (10 mu g/kg) or an equal volume of normal saline. Tracheal intubation was performed 10 min after anesthetic induction. Mean arterial pressure, HR, SpO(2), and BIS were recorded during the 15 min-anesthesia induction. From 2 to 5 min after tracheal intubation, BIS was significantly higher in the atropine group than in the control group (p = 0.043, 0.033, 0.049, and 0.001, respectively). When compared with baseline values (immediately before intubation), BIS showed a significant increase at 1 min after intubation in both groups, without intergroup differences, whereas it decreased significantly from 4 to 5 min after intubation only in the control group. This study demonstrated that atropine maintained BIS increases in response to endotracheal intubation during anesthetic induction with propofol and remifentanil TCI, although the maximal response did not differ between the groups.