The objective of this study was to determine the effect of a constant rate infusion of medetomidine in the cortical brain activity and hemodynamic parameters in sevoflurane anesthetized puppies. Six puppies of the age of two weeks old were included in the study and were anaesthetized three times with sevoflurane. On the first anesthesia, each dog’s minimum alveolar concentration (MAC) for sevoflurane was determined by the use of the tail clamp method. On the second anesthesia (S) the puppies were anesthetized at each of five multiples of their individual’s MAC, 0.75, 1, 1.25, 1.5 and 1.75 MAC, and bispectral index and cardiorespiratory parameters were registered. On the third anesthesia (SM), puppies were anesthetized at each of five multiples of their individual’s MAC and medetomidine (5 µg/kg + 2µg/kg/h) was administered. Mild cardiovascular depression was observed in SM in comparison with S. Cortical and antinociceptive effects were not observed with medetomidine infusion although a mature EEG response to noxious stimulation would not have developed in puppies. Central alpha-2 adrenoreceptors would be immature in puppies during the first two weeks of life, and for this reason, medetomidine would not produce sedative and analgesic effects in young puppies. More studies have to be performed to support this statement.

Key words: Bispectral index, Infusion, Medetomidine, Puppy, Sevoflurane