NEUROMUSCULAR BLOCKING-DRUGS DO NOT ALTER THE PUPILLARY LIGHT REFLEX OF ANESTHETIZED HUMANS

Objective: To test the hypothesis that systemically administered neuro muscular blocking drugs acutely alter resting pupil size or the direct reflex response to light in anesthetized humans. Design: Patients wer e 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. Settin g: The University of California, San Francisco, Moffitt-Long Hospitals . Patients: Healthy adults (American Society of Anesthesiologists phys ical status I or II) of either sex scheduled for elective surgery requ iring general anesthesia, tracheal intubation, and muscle relaxation o f an anticipated duration of 2 or more hours. Main Outcome Measures: M easurements of resting pupil size, direct reflex response to light, an d 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 vecur onium or pancuronium. Tetanic stimuli and concomitant isoflurane admin istration respectively increased and decreased pupillary light reflex amplitude, indicating that pupillary responses were not fixed. Conclus ion: We conclude that systemically administered neuromuscular blocking drugs (vecuronium and pancuronium) do not acutely affect the pupillar y light reflex in healthy, anesthetized patients.