Neuromuscular blocking drugs do not alter the pupillary light reflex of anesthetized humans
A. T. Gray, S. T. Krejci and M. D. Larson
Department of Anesthesia, San Francisco General Hospital, Calif, USA.
OBJECTIVE: To test the hypothesis that systemically administered
neuromuscular blocking drugs acutely alter resting pupil size or the direct
reflex response to light in anesthetized humans. DESIGN: Patients were
randomized to receive an intravenous injection of saline (0.15 mL/kg),
pancuronium bromide (0.1 mg/kg), or vecuronium bromide (0.15 mg/kg) after
induction of general anesthesia and tracheal intubation. SETTING: The
University of California, San Francisco, Moffitt-Long Hospitals. PATIENTS:
Healthy adults (American Society of Anesthesiologists physical status I or
II) of either sex scheduled for elective surgery requiring general
anesthesia, tracheal intubation, and muscle relaxation of an anticipated
duration of 2 or more hours. MAIN OUTCOME MEASURES: Measurements of resting
pupil size, direct reflex response to light, and constriction velocity were
obtained in double-blinded fashion using infrared pupillometry. RESULTS:
Pupillary size, reflex amplitude, and constriction velocity were not
altered by the presence of either vecuronium or pancuronium. Tetanic
stimuli and concomitant isoflurane administration respectively increased
and decreased pupillary light reflex amplitude, indicating that pupillary
responses were not fixed. CONCLUSIONS: We conclude that systemically
administered neuromuscular blocking drugs (vecuronium and pancuronium) do
not acutely affect the pupillary light reflex in healthy, anesthetized
patients.
