The administration of fentanyl with propofol reduces the blood concentration of propofol required to achieve adequate anesthesia for tracheal intubation. However, different intubation procedures have variable intensities of noxious stimulation and may require different levels of anesthesia. The goal of this study was to determine the propofol blood concentration at which 50% of patients did not respond to stimulation (Cp50) for laryngoscopy, intubation with a laryngoscope, insertion of a slotted oral-pharyngeal airway (Ovassapian airway), and intubation with a fiberscope when administered in conjunction with fentanyl. Patients undergoing elective surgery were given varying amounts of propofol or propofol with fentanyl, and their responses to the four procedures listed above were assessed. These experiments demonstrated that the propofol concentration required for intubation with a laryngoscope was similar to that for intubation with a fiberscope, and that the required level was reduced by fentanyl. Hemodynamic responses to intubation were lower with a fiberscope than with a laryngoscope. We conclude that almost the same concentrations of propofol or fentanyl are necessary for suppressing both of the somatic responses to tracheal intubation with a fiberscope or a laryngoscope. Hemodynamic responses were attenuated more during intubation with a fiberscope.
Implications: The propofol blood concentrations at which 50% of patients did not respond to stimulation for laryngoscopy, tracheal intubation with a laryngoscope, and tracheal intubation with a fiberscope were 10.9, 19.6, and 19.9 microg/mL, respectively. These were reduced by fentanyl. Hemodynamic responses to intubation were less with a fiberscope than with a laryngoscope.