Influence of Atropine on the Dose Requirements of Propofol in Humans

Abstract

  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 μg 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 μg 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<0.0001). Propofol concentration was significantly decreased from 2.12±0.28 to 1.69±0.27 μg mL^-1 (p<0.0001).
  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.