The feasibility of recording blink reflexes under general anesthesia

Until now, there have been no reports on eliciting the blink reflex (BR) during anesthesia at a depth compatible with surgery. We introduce a novel method for eliciting the R1 component of the BR under inhalation or total intravenous anesthesia by using a short train of four to seven stimuli applied over the supraorbital nerve. Recording is done from the ipsilateral orbicularis oculi muscle. We set out to record the BR in 27 patients (age 1-78 years) without involvement of the facial nerve, trigeminal nerve, or brainstem. The BR could not be recorded in only 4 patients (recordability: 86.2%). All patients received at least one bolus of propofol while in surgery. Using this method, the BR was recorded on 4 awake healthy subjects. Boluses of propofol and muscle relaxants should be avoided in order to successfully record the responses. BR recording is feasible in patients under general anesthesia by using this novel technique.