Evaluation of aqueous tear production in dogs after general anaesthesia with medetomidine-propofol-carprofen-halothane.

The influence of an anaesthetic protocol, which included medetomidine, propofol, carprofen and halothane on tear production in the dog. There are no previous studies on the effects of this combination on tear production in dogs or in any other species. The present study included 39 dogs, which underwent non-ophthalmic surgery in our clinic. Preanaesthetically, all dogs had normal tear production (18.62±3.65 mm/minute) as this was recorded with Schirmer tear test I (STT I) and the ophthalmologic examination did not reveal anything abnormal. Tear production readings were recorded before the administration of premedication, at the end of anaesthesia, one hour and two hours postanaesthesia. No reverse agent was administrated. At the end of anaesthesia (right eye (oculus dexter, OD) P<0.0005, left eye (oculus sinister, OS) P<0.0005), as well as one hour postanaesthesia (OD P=0.020, OS P=0.001) there was a statistically significant reduction in tear production, which returned to normal values two hours postanaesthesia, regardless of the duration of the operation. This anaesthetic combination resulted in a decrease in tear production and, therefore, the use of tear substitute treatment in dogs undergoing anaesthesia with this protocol (combination) from the time the sedative is given until at least two hours after the end of anaesthesia is highly recommended.