Effects of general anesthesia on the human blink reflex

Abstract

The blink reflex was studied in 10 patients undergoing elective procedures under general anesthesia. Anesthetic agents were isoflurane, halothane, nitrous oxide, methohexital, and thiopental in various combinations. At induction, blink reflexes were diminished by low-dose thiopental (1-1.5 mg/kg) and abolished by high-dose thiopental (4-8 mg/kg) and methohexital (1.5 mg/kg). Blink reflexes were absent during halogenated volitile inhalational anesthesia and did not return until patients were in the recovery room, well after end-tidal anesthetic levels were zero by mass spectroscopy. Recovery of consciousness and the ability to blink on command often preceded return of any blink reflex activity, indicating that the blink reflex is not useful as a postoperative test of facial nerve function in the operating room after anesthesia. In six patients, blink reflexes were still diminished 2-3 hours after cessation of anesthesia, at a time when patients were fully oriented and corneal and eyelid reflexes were clinically normal. This finding suggests that the blink reflex might be a sensitive test of subtle CNS dysfunction after inhalational anesthesia and potentially could serve as a useful objective indicator of recovery from anesthesia for outpatient surgery.

The feasibility of recording blink reflexes under general anesthesia

“…10,[13][14][15] The exception was in patients with hemifacial spasm in whom the R1 component could be elicited. 11 Montero et al 12 recently presented evidence that report of BRs elicited during general anesthesia in patients with hemifacial spasm, recorded by Moller and Jannetta, 11 was in fact a phenomenon of "lateral spreading," initiated by antidromic activation of the facial nerve instead of trigeminal afferents.…”

Optical modelling of a supplementary tunable air-spaced goggle lens for rodent eye imaging

“…This can be best achieved under Lab experiment when the goggle lens is fastened onto the system and lens alignment monitored by moving the eye with respect to the goggle lens fixed [8,10]. In fact, for an anesthesized eye, blink reflexes can be appreciably diminished, and even abolished [25], which permits an optimal and steady placement of the lens for the use of an artificial cornea. However, in absence of sufficient level of anesthesia, blinks are expected to affect the optimal optical performance of an artificial lens alone, as shown in Fig 5.…”