Influence of Atropine on the Dose Requirements of Propofol in Humans

Summary: Objective: The purpose of this study was to evaluate the effect of atropine on the dose requirement of propofol for induction of anesthesia and propofol concentrations during continuous infusion. Methods Study 1: Forty patients were randomly allocated to the control or atropine groups. Induction of anesthesia commenced 3 min following the administration of 0.9% saline or atropine (0.01 mg kg" 1 ), using a Diprifuser set to achieve propofol concentration of 6.0 Mg mL" 1 . The primary end point was the propofol dose per kg at the moment of loss of response to a command. Study 2: Fifteen patients undergoing elective surgery were enrolled. Propofol was administered to all subjects via target-controlled infusion to achieve a propofol concentration at 2.0 Mg mL" 1 after intubation. Before and after administration of atropine (0.01 mg kg" 1 ), cardiac output (CO) was measured using indocyanine green as an indicator and blood propofol concentration was determined using high-performance liquid chromatography. Results Study 1: The propofol dose for each group was 2.22 ± 0.21 mg kg" 1 for control group and 2.45 ± 0.28 mg kg" 1 for atropine, respectively (p = 0.014). Study 2: After the administration of atropine, CO was significantly increased from 4.28 ± 0.83 to 5.76 ± 1.55 l min" 1 (p  1 (p  Conclusions Following the administration of atropine, the propofol requirements for the induction of anesthesia were increased and propofol concentrations were decreased during continuous infusion by the administration of atropine.