Effect of anaesthetic premedication with medetomidine-buprenorphine on the aqueous tear production in dogs

The Schirmer tear test (STT) was performed in 28 healthy dogs and five dogs with dry-eye syndrome before anaesthesia and 10 and 30 minutes after anaesthetic premedication with medetomidine (20 mug/kg) and buprenorphine (10 mug/kg). All healthy dogs had normal preanaesthetic STT values (16.9 +/- 1.08 mm/min). STT values 10 minutes after premedication were highly significantly decreased (p < 0.01) from the normal values to critical value (1.7 +/- 0.94 mm/min) and after 30 min STT was undetectable (STT 0 mm/min.). Dogs with dry-eye syndrome had preanaesthetic STT 6.4 +/- 0.18 mm/min. In comparison with healthy dogs, in this group STT values were undetectable (STT 0) already 10 min after premedication (p < 0.01). The age, breed, sex and body weight of the patients did not significantly influence the STT results. Medetomidine (20 mug/kg) with buprenorphine (10 mug/kg) is a good anaesthetic premedication that induces profound sedation and analgesia. STT was recommended as a part of preanaesthetic examination, and eye protection should be performed in each dog premedicated with medetomidine-buprenorphine to prevent corneal damage.