RELATIONSHIP BETWEEN PUPIL SIZE AND ACETYLCHOLINESTERASE ACTIVITY IN PATIENTS EXPOSED TO SARIN VAPOR

Objective: To elucidate the effect of sarin vapor on pupil size and er ythrocyte acetylcholinesterase activity (AchE). Design: Retrospective observational survey. Setting: Emergency department of an urban teachi ng hospital. Patients: 80 patients who were exposed to sarin in a terr orist attack in Tokyo subways. Measurements and results: Pupil size an d AchE activity on the day of exposure were measured. Among the 80 pat ients, the pupils were miotic (< 3 mm) in 50 patients (62.5 %), while AchE activity was below the normal range (< 1.2 U) in 34 patients (42. 5 %). AchE was significantly lower in the miotic group than in the gro up with normal pupils (1.0 +/- 0.5 U vs 1.5 +/- 0.3 U, p < 0.01). In t he miotic group, AchE activity was lower than normal in 32 patients (6 4.0 %) but was decreased in only 2 patients in the normal pupil group (6.7 %) (p < 0.01). Conclusions: Miosis is a more sensitive index of e xposure to sarin vapor than erythrocyte AchE. Systemic poisoning is ap parently less likely to develop if the patient's pupil size is normal on arrival at the hospital.