Decreased tear production associated with general anesthesia in the dog

Schirmer I tear tests were done on 20 dogs before and during general anesthesia. Atropine sulfate reduced tear production from a mean base-line value of 20.35 +/- 3.33 mm/minute to 14.10 +/- 6.13 mm/minute, 10 minutes after its subcutaneous administration. The combination of subcutaneous atropine, intravenous thiamylal sodium, and inhalation anesthesia reduced tear production to a mean value of 0.53 +/- 1.12 mm/minute at 60 minutes after induction.